'^v* :,y ^ iVv^v, ^'i'Cr V .*''*, ^«! %.^^ ,y ^ ^^•^^^ ,-^°*v • ^^' e »» ' C, vP » A^-^ ► 'i:^ -^^ \J -o , K - -• y T. J, % " -^^ o-^ °o ^^* ^^ .-Jv^ r . oV / \*^f^\/ V^^*/ \^^^\/ %^^-.o^ \'^%.^ -^^ 4 0*. «Ho^ o* > ^-to* .4 ^-^^^ 4^ ^ s''^-. <> "^T^T^- . 'J^-,. 'O, ^^^o'^."..^^^ ••- .^"..--* -^o ^VcO^.-,.-^^ •• .^"..v-. -^^ -" J>^ .0- ^^ "^^V^ ^\.^^^-^ X .' ;* , -^^ ^"-^K V «» *^ 4C)k ^: t^'-n.^. S'^^ ^^' ^ •ft, 1* ■' %,«* **■ •\/ -'^ Bureau of Mines Information Circular/1984 Microcomputer-Based Monitoring and Control System With Uranium Mining Application By C. T. Sheeran and J. C. Franklin UNITED STATES DEPARTMENT OF THE INTERIOR miMMB Information Circular 8981 I* Microcomputer-Based Monitoring and Control System With Uranium Mining Application By C. T. Sheeran and J. C. Franklin UNITED STATES DEPARTMENT OF THE INTERIOR William P. Clark, Secretary BUREAU OF MINES Robert C. Norton, Director o(d Library of Congress Cataloging in Publication Data: Sheeran, C, T. (Christopher T,) Microcomputer- based monicoring and control system with uranium mining application. (Information circular / United States Department of the Interior, Bureau of Mines ; 8981) Bibliography: p. 24. Supt. of Docs, no.: I 28.27:898*1. 1. Uranium mines and mining— Safety measures— Data processing. 2, Microcomputers. 3. Real-time data processing. I. Franklin, John C. II. Title. III. Series: Information circular (United States. Bu- reau of Mines) ; 8981. -TN^5,U4 [TN490.U7] 622s [622'.8] 84-600091 ^ CONTENTS '^ Page Abstract 1 Introduction 2 System description 3 rT^ Hardware 3 ^ Central processor 3 v^ Data-event printer 4 Communication trunk 4 Accessors 4 Binary accessors 4 Analog accessors 5 Modems 9 Software 9 Operating system 9 Application software 9 Main scan program 11 Command service. 14 Alarm printer service 14 CRT display service 14 Event sequencing 16 Installation 17 System use 18 Startup procedure 19 Data entry 20 Operation 20 Uranium mining applications 23 Records 23 Sequences 23 Conclusions 23 References 24 Appendix. — Analog accessor calculations 25 ILLUSTRATIONS 1 . Basic system hardware 3 2. Pulse-integrating accessor and continuous working level monitor 6 3 . Functional block diagram of PI accessor 8 4 . System memory map 10 5 . Status from different accessor types 11 6 . Flow diagram of scan procedure 12 7 . CRT display areas 15 8. CRT data display 15 9 . Block diagram of surface equipment hookups 18 TABLES 1. Accessors evaluated for uranium mining applications 5 2. Count period dipswitch assignments for pulse-integrating accessors 7 3. System commands sorted by function 21 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT ft/mln foot per minute min minute h hour ms millisecond in inch pet percent kHz kilohertz s second km kilometer V ac volt, alternating current L liter V dc volt, direct current m meter WL working level MeV million electron volts WLM working level month MICROCOMPUTER-BASED MONITORING AND CONTROL SYSTEM WITH URANIUM MINING APPLICATION By C. T, Sheeran and J» C« Franklin ABSTRACT The Bureau of Mines investigated a microprocessor-based real-time con- trol and monitoring system for uranium mining applications. The system is capable of controlling and monitoring up to 768 stations within 3 km of the central processor on a common four-wire cable. It can be used in conjunction with detectors to continuously monitor and display radiation working levels at points throughout the mine. Surface alarms are sound- ed for critical situations such as rapid radiation buildup, loss of pow- er to monitors or fans, and changes in air door position. Permanent records of all changes are automatically printed out with their time of occurrence. Printouts can also be obtained for shift reports or trend logs. The system can be used to remotely control fan startup and shut- down, and also can alert miners of underground conditions by blowing horns or turning on lights. Battery backup keeps the system operative for up to 4 h in case of a mine power outage, A special software fea- ture permits automatic, time-delayed, sequential restart of fans. ^Mining engineer, ^Supervisory physical scientist. Spokane Research Center, Bureau of Mines, Spokane, WA. INTRODUCTION In protecting the health and safety of underground personnel, the mining indus- try must contend with the radioactive gas radon and its daughter products. Radon and radon daughters are decay products of uranium and are found in nearly all types of mines. However, the extreme concen- trations of these daughters in uranium mines present a greater health hazard than that found in other types of mines. The radon daughters polonium-218 and polonium-2lA emit alpha particle radia- tion that may induce certain forms of cancer. Exposure to these daughters in mine air has been shown to produce a high incidence of lung cancer among uranium miners (J_).^ Present Federal safety standards state that the maximum allowa- ble concentration of radon daughters in a work environment is 1 WL unless respira- tors are worn. Total exposure per person is limited to 4 WLM for any calender year.^ Most of the uranium produced in the United States is mined from sandstone formations, which have high porosity and permeability and which may be highly fractured. Because of this, radon is re- leased from the sandstone very readily, and its emanation rate can be profoundly increased by a slight decrease in baro- metric pressure. Ventilation techniques that employ blowing, exhausting, and push-pull fan combinations are used by the industry to supply adequate air quantities to reduce . the radon daughter concentrations. As uranium mines have become larger and ■^Underlined numbers in parentheses re- fer to items in the list of references preceding the appendix. '^One working level is defined as any combination of short-lived daughters in 1 L of air that will result in the ulti- mate emission of 1,3 x 10^ MeV of alpha energy. This includes the radon daugh- ters from polonium-218 through polonium- 214. The working level month is defined as the working level exposure multiplied by the hours exposed, divided by 173. deeper, and electrical costs have risen, ventilation costs have increased sharply — ventilation now accounts for a major portion of underground uranium mine production expenditures. Bates (2^) es- timated that in order to comply with the 4-WLM standard, these costs ranged from $4.68 to $5.41 per ton of ore removed in 1980. This estimate included costs for electricity, ventilation shafts, fans, vent bags, and other associated equipment . An interruption in mine power, causing fan shutdowns, can produce drastic changes in the radon and radon daughter concentrations. Sometimes shutdowns may go undetected for some time. Franklin (3^) and Musulin (4-5^) have shown that fan shutdowns of 5- to 30-min duration can increase radon concentration to three to five times normal, Franklin (6^) reports that the mining activities of slushing and blasting may increase this concentra- tion up to 40 and 400 pet, respectively. The uranium industry presently uses Kusnetz sampling to determine personnel exposure and to detect areas where ven- tilation changes are needed to maintain desirable radon daughter levels. These samples are taken at various intervals ranging from daily to monthly, depending on radiation concentration and sampler availability. Kusnetz-type samples are usually very accurate point-in-time mea- surements. However, since concentrations are continually changing, more continuous methods of monitoring are needed to mini- mize miner exposure. Continuous monitor- ing can provide data never before availa- ble to ventilation engineers, which can be used to optimize the ventilation network. The Bureau of Mines has been investi- gating instrumentation that can help in detecting excessive working levels. Droullard (7) devised a continuous work- ing level monitor that has been used for several years in the Bureau's research activities in both experimental and active mines. Shaw and Franklin (8^) took this continuous working level monitor and interfaced it to a microcomputer to cre- ate an alarm system, which has been suc- cessfully field-tested. It was concluded from the field test that an alarm system with expanded capabilities would be more useful to the ventilation engineer. Therefore, work began on the new system described in this report. SYSTEM DESCRIPTION The system investigated is a modified Senturion-2005 manufactured by Conspec Controls, Ltd. Modifications were per- formed by Conspec in both hardware and software according to Bureau specifica- tions, and the Bureau has made further hardware modifications to the system for mine use. Much of the following informa- tion was derived from Conspec manuals (9). HARDWARE The Senturion-200 is advertised as a "microcomputer-based real-time data ^Reference to specific trade names and manufacturers is made for identification purposes only and does not imply endorse- ment by the Bureau of Mines. acquisition, monitoring, and control sys- tem." Its basic hardware consists of a central processor, data-event printer, communication trunk, and accessors , as illustrated in figure 1. Modems may also be included with the system for long- distance operation. Central Processor The central processor is a desktop unit that contains the main processor, video terminal (CRT), keyboard, disk drive, and accessor trunk drivers. The main processor is a Zilog-based microcom- puter system that uses a Z80A central processing unit with both parallel and serial input-output (I/O) ports. Memory consists of 65,536 (64K) bytes of dynamic Accessor Accessor FIGURE 1. - Basic system hardware. random-access memory (RAM) , with an addi- tional 7.168 (7K) bytes of erasable, pro- grammable read-only memory (EPROM) . A floppy-disk controller is used to inter- face to the system disk. Other compo- nents include direct memory access (DMA) logic, an on-board programmable read-only memory (PROM) programmer, and a four- channel counter-timer. An Intel 8080 microprocessing unit is used to control the CRT and keyboard. The alphanumeric keyboard is similar to the keyboard of an office typewriter, with additional special function keys used to simplify operator commands when in the main program. The system disk uses 8-in, single-sided floppy disks and provides 131,072 (128K) bytes of additional memory. Disks are used as nonvolatile storage for programs and data. Data-Event Printer A Teletype 43RO printer is used with the system for character-at-a-time , receive-only operation. The system is programmed for automatically and manually requested printouts. Automatic printouts are obtained for all alarms and events with their corresponding time of occur- rence. The printer can also be requested from the keyboard to print descriptions, shift reports, trend logs, and other sys- tem configurations and parameters. Communication Trunk The communication trunk is a data chan- nel through which the system communicates with the accessors. The trunk is con- nected to the central processor via an RS-232 interface and to the accessors via a single four-wire shielded cable. The trunk uses two of these wires to provide 24-V dc power to the accessors; the re- maining two wires are used to transmit and receive digital signals. Trunk- to-accessor communication is asynchronous at 4,800 baud. Accessors Accessors manufactured by Conspec pro- vide the interface between the system and the field devices to be monitored or con- trolled. At the heart of each accessor is an addressable universal asynchronous receiver and transmitter (UART) chip. This chip has an asynchronous data format consisting of a serial stream of data bits preceded by a start bit and followed by a stop bit. The UART receives two eight-bit words in a serial data stream from the processor; the first word re- ceived is an address , and the next is a command. When the address sent matches the programmed address of the receiver, the transmitter is enabled to transmit two data words consisting of accessor identity and status. Each accessor is actually a point mul- tiplexer with its own unique dipswitch- selectable address variable from to 127. An identity (ID) dipswitch on the accessor card permits the user to select the binary word that will be used by the processor to interpret the incoming data. Accessors are classified as either ana- log or binary. Both types of accessors were purchased for field testing in ura- nium mining situations. Table 1 is a list of accessors evaluated with the system. Binary Accessors Binary accessors control and/or report status from contacts. Three kinds of these accessors were used in mine tests to perform such jobs as turning on mine fans, flashing warning lights, or turning on underground alarm lights . Binary ac- cessors used include the Bl, B2, and B25 types. Bl Accessor The Bl accessor is used to monitor the condition of a field-mounted supervised contact. Each accessor can handle one TABLE 1. - Accessors evaluated for uranium mining applications Accessor' Type Data entry code ID dipswitch 7 6 5 4 3 2 10 1 5 4 00000000 00000000 (2) 10 10 10 7 2 1110 10 A5 (A). A8 (A). PI (A). Bl (B). B2 (BC), B25 (BC), B26 (AC), Process Potentiometric , Pulse-integrating. . , Single binary 2-state commandable binary, 5 output. ........... Setpoint (6 output). 'Accessor classification: A = analog; AC = commandable analog B = binary; BC = commandable binary. 2 Hardwired. function point and receives its input from a normally closed or normally open dry contact switch. Proper installation of end-of-line resistors enables the ac- cessor to monitor and detect sensor line faults. The contact sensor may be lo- cated up to 30 m from the accessor. The Bureau used this accessor as a bulkhead door position monitor, ventila- tion fan monitor, and mine power monitor. It has also been used in conjunction with the pulse-integrating accessor (analog) to detect power interruption and sensor line faults for the continuous working level monitors. from the surface. It could also be used in conjunction with a sequencing program to automatically restart fans in sequen- tial order after a power bump. B25 Accessor The B25 is a commandable accessor simi- lar to the B2, except that it can control up to five outputs. As with the B2, the accessor is used with an SRP to interface accessor circuitry to circuits having other voltages and currents. The B25 accessor cannot be used, however, to give flow status; it can only be used to turn devices on or off. B2 Accessor The B2 accessor is used for command controlling of any two-state, remotely located field device. The accessor is used with a slave relay package (SBIP) to interface accessor circuits with other voltages and currents. Used together, the accessor and SRP can start and stop motors, open and close dampers, or con- trol other two-state functions. The ac- cessor can also be used to monitor status and alarm conditions of motors not di- rectly commanded from the terminal. When proof-of-flow status (verifying that de- vice state matches commanded state) is required, the accessor and SRP can accom- modate either an ac or dc contact switch. In Bureau tests, this accessor was used to control underground ventilation fans Although the B25 occupies one address, it contains five different, individually selectable points. This accessor has been used in conjunction with sequencing programs to provide a central alarm indi- cator in mine tests. In this capacity, it has been used to drive light-emitting diode (LED) indicators, which represent specified mine conditions such as a work- ing level alarm. The central alarm indi- cator was located to provide a quick visual determination of current alarm conditions for underground personnel. Analog Accessors Analog accessors convert analog signals or pulses from field devices to digital form. The digitized value is then sup- plied to the processor upon interroga- tion. Four different types of these c o E > JO) c o ? w z> o 3 c c o u •o c D O w w o o u o c 0) DL ID o accessors were tested by the Bureau: A5 , A8 , B26, and pulse-integrating (PI) types. A5 Accessor The A5 is a process-type eight-bit ac- cessor that is used with a field device to monitor the condition of a dynamic process. The signals from the appropri- ate sensors are converted into analog values by a process transducer. The A5 accessor will accept and digitize an ana- log value within the range of to 5 V dc. The process transducer may be lo- cated up to 160 m from the accessor with- out loss of accuracy. The Bureau has used A5 accessors with J-Tec anemometers and with temperature and relative humidity sensors. A8 Accessor The A8 is a potentiometric-type eight- bit accessor that is used with a remotely located potentiometric sensor. Such a sensor can be used to monitor pressures or the position of a damper or other de- vice. This accessor can be used with any three-wire, full-travel potentiometric sensor that has a full-scale span between 2,000 and 10,000 ohms. The sensor may be located up to 160 m from the AS accessor. B26 Accessor was used with a sequence triggered by alarm conditions (such as working level, power-off , or sensor line fault) to turn on LED indicators. Pulse-Integrating Accessors The PI accessor card shown in figure 2 was built by Conspec according to Bureau specifications. This 16-bit accessor was designed to interface to continuous radi- ation monitors designed by the Bureau to measure radon and working level concen- tration (7^, 11 ) . These monitors output random, transistor-transistor logic (TTL) compatible pulses; the number of pulses per unit of time is proportional to radi- ation concentration. A block diagram of the PI accessor is shown in figure 3. This accessor accepts the TTL-compatible pulses at a single in- put and divides the input pulse frequency by a selectable factor (prescaler) . The prescaler is selectable from 2 to 255 and is entered as an eight-bit binary number at dipswitch S22. After being divided by this factor, the pulses are fed to a 16- bit binary counter where they are accu- mulated for a fixed period of time (count period) . This period is selectable from 0.4 to 819 s (13 min, 39 s) in increments of 0.2 s and is set as a binary number on dipswitches S20 and S25. Weights as- signed to each rocker switch are shown in table 2. The B26 accessor is a binary setpoint accessor with a resolution of six binary bits. It is similar to the B25 (binary) except that the outputs are not indi- vidually controlled. It is classified as a commandable analog accessor. The six outputs are controlled by position and have 64 different binary combinations of enabled or disabled states. Position corresponds to all outputs enabled; posi- tion 63 to all outputs disabled. This accessor can be used with other hardware logic to vary motor speeds or to adjust louvre positions. The B26 has been used by the Bureau to provide alarm indicator lights for the PI accessor. In this application, the B26 TABLE 2. - Count period dipswitch assign- ments for pulse-integrating accessors Dipj switch Rocker Weight , s S25., 4 3 409.6 204.8 2 102.4 1 51.2 S20.. 8 7 25.6 12.8 6 6.4 5 3.2 4 1.6 3 .8 2 .4 1 .2 S22 I I I I I I I I Pulse input Conditioner D ips w i t c h to select N (2-255) Prescaler -r N Reset ^ 16-bit counter Latch 16 MSB -C-JZ bit latch LSB Time base generator 0.4 s-13 min S20- S25 UART MUX Select Clock 307.2 kHz Mill lllllll Dips witch to select time base ID switch Address switch Data in ID in Address in 5_i Trunk interface ^ 1 To accessor trunk FIGURE 3. - Functional block diagram of PI accessor. (LSB = least significant byte; MSB = most significant byte; MUX = multiplexor.) The maximum accumulated count of this accessor is hardware-restricted to the 15-bit count value of 32,767; the pre- scaler and count period should be se- lected to meet this requirement. Two LED's located on the accessor cir- cuit card indicate the presence of an input pulse train and count period re- set, respectively. These LED's, off in normal operation, are enabled by switch- ing rocker 8 of S25 to the on position. Troubleshooting and calibration proce- dures may involve the use of these LED's. When the PI is interrogated during the scan, it will provide the processor with the last completed accumulated total. An on-board 16-bit register is used to save this last completed count. Since the data transmission to the processor is byte oriented, the processor requires two interrogations to obtain the full 16 bits of data. The ID dipswitch of the PI accessor, unlike that of other accessors, is hard- wired and, therefore, not selectable. When this ID is received during an inter- rogation, the processor calls a special software routine to handle the two re- turned data bytes. The 8 most signifi- cant bits of the 16-bit total are then used in calculations and in alarm processing. Modems Points many miles away from the proces- sor, such as those at another mine, can be monitored and controlled through modems. The modems, called long-distance accessors (LDA's), consist of a local and a remote unit. The local LDA is connect- ed to the communications line as an ordi- nary accessor and requires 110-V ac pow- er. Data transmission between this unit and the remote LDA may take place on dual, metallic-shielded, twisted-pair conductors or on a half-duplex, leased, 3,002 voice-grade telephone line. Dis- tance limitations are as follows: up to 2.7 km with 18 American wire gauge (AWG) dual cable, and up to 6,400 facility km with the leased telephone line. Several remote LDA units can be used with a sin- gle LDA local unit. Each message sent between modems is du- plicated and slowed down to 600 baud. When receiving, the modems compare dupli- cate messages for errors , then increase transmission rate to 4,800 baud into the accessor trunk line. The remote LDA functions also as a remote accessor trunk by providing +24 V dc and 4,800-baud transmission to its connected accessors. SOFTWARE Senturion-200 software is made up of two parts: the operating system and ap- plication programs. The operating sys- tem used is a control program for mi- croprocessors (CP/M) (10). Applications programs written by Conspec accomplish data acquisition, monitoring, and control of the various points. Operating System CP/M consists of programs that execute user commands and access hardware re- sources such as the CRT and printer. The basic system executive and boot-strapping programs reside in EPROM memory to enable the CP/M to be transferred from disk to RAM on powerup, CP/M commands consist of both resident and transient directives. Resident commands are "built in" and can be used to read the current disk direc- tory (DIR) , erase files from the disk (ERA) , rename files (REN) , type out con- tents of a file to the CRT (TYPE) , and save the contents of memory as a file on the disk (SAVE), Transient commands such as DDT, ED, MOVCPMM, PIP, SYSGEN, and XDIR are known as utilities. These have a file type of ,C0M and will appear in the directory if present. These commands enable the user to debug programs (DDT) , create and edit files (ED) , alter the CP/M image size (MOVCPMM) , copy files from one disk to another (PIP) , copy the CP/M boot onto new disks (SYSGEN), and look at files in alphabetical order with file size listed (XDIR) , These resident and transient commands are explained in detail in CP/M manuals. Application Software Once the CP/M is booted, the user can enter into application programs written by Conspec, These various programs per- form in concert with each other and com- prise the main program, A keyboard com- mand (see "Startup Procedure" section) begins the loading sequence, which first alters the RAM configuration and then loads files stored on disk. For the Bureau's system, the following files are loaded: 1, S200BAS — main operating software, 2, PRNIOP — printer-operation software, 3, NLDAOP — modem-timing software. 10 4. SHRIOP — shift-report software. 5. RADNOP — pulse-integrating accessor software. 6. ESQ203 — event-sequencing software. After loading each of these files, the computer will display memory locations and other data. The locations corre- spond to slots in the startup procedure area shown on the Senturion memory map (fig. 4). When loading is complete, the main program starts and runs in a con- tinuous loop to perform the monitoring and control functions. While in this mode, only application commands are ac- cepted (CP/M commands are invalid) . FFFF Status saved on and read from disk Startup CP/M-DDT Special tables CF-OFS tables status buffer Scan buffer Alarm buffer Specials and custom software Main operating software Variables and flags Units and mode 1/2, 3/4 tables I/O device buffers ( printer and CRT ) Reserved for CP/M Interrupt vector table and disk drive commands FIGURE 4. • System memory_ mop. 11 Application programs include the main scan program, command service, alarm printer service, CRT display service, and other software such as the sequencing program. Main Scan Program Once in the main program, the processor continuously sends messages to the acces- sors in a predetermined sequence. Mes- sages consist of an address and a command to which the appropriate accessor responds by returning its identity and status. Status consists of digitized in- formation, which may represent an analog reading or the position of contacts, as shown in figure 5. After requesting information from an accessor, the processor waits several milliseconds for data to be returned. During this time, it performs the remain- der of its tasks such as updating the CRT or performing calculations. If no data are returned, as in the case of broken communication lines, a communication-fail alarm is generated. The processor then continues with the scan, starting with the next address. A flow diagram of the scan procedure is shown in figure 6. The scan checks only those accessors that the operator has enabled through the key- board. Scan time per accessor is on the order of 10 ms; total scan time depends upon the number of enabled accessors on- line. The presence of modems in the sys- tem slows down the scan time. For binary points, received data are checked against the last valid reply re- ceived. If they match, the message is ignored and no updating of status occurs. With analog points, the received data are checked for normal or alarm condition, and the delay-to-alarm counter (up to 255-s delay permitted) is updated accord- ingly. If there is a change in the data Central processor Accessor value Accessor value Contact status Command Contact status PI accessor B1 accessor B2 accessor Analog voltage Anemometer Pulses Contacts ANALOG — II — Normally open I '-^4f—' Normally closed BINARY Relay Fan motor FIGURE 5. - Status from different accessor types. 12 Update scan address counter Yes Set end-of scan flag Reset try counter Set transmit flag Transmit data Restart timer Main line r^ start J ? FIGURE 6. - Flow diagram of scan procedure. 13 Increment trycounter Set up the error code Fill print CMD buffer Increment trycounter Retransmit ^ ^^1S\,Yes Transmit Restart ^xecute^^^' timer |No JT ^^D irN^ progress^ Set CMD progress flag Tno FIGURE 6. - Flow diagram of scan procedure -Continued. 14 received, the processor determines the nature of the change and records this in- formation in a temporary buffer. From there, the information is decoded and displayed on the CRT and printed if desired. Command Service Command requests may originate from either the keyboard or from a programmed event sequence. It is possible for both to be in simultaneous operation on a time-share basis. Command requests are prioritized when issued, and a system executive processes them for priority before passing them to a command execu- tion routine. A successful execution is printed out as an event on the printer and also displayed as a status change on the CRT. If a command initially fails, the processor will try again twice more before printing out a code of the failure on the printer. Alarm Printer Service The user determines at the time of data entry whether a point's events will be printed. It the print option is chosen, an occurring event (change of state) causes an internal buffer to be filled. These data are then transferred to the printer. The format observed for these messages is shown below, followed by an example printout for both binary and ana- log points. TIME PT. NO. DESCRIPTOR MODE 1/2 MODE 3/4 STATUS 10:19:30 30 965 FAN MONITOR ON NORMAL 11:14:01 17 WL#207 (ESCAPE) HIGH ALARM 13:09:00 17 WL#207 (ESCAPE) NORMAL 14:00:42 1 807 COM. FAN OFF ALARM 15:33:58 1 OFF COMMD EXEC 15:33:58 1 807 COM. FAN OFF NORMAL VALUE 1.0004600 WL 0.9923400 WL STATUS indicates the condition of the point and will be one of the fol- lowing: NORMAL, ALARM, communications failure (C.FAIL), communications restored (CREST), sensor lines open (SLO), or sensor lines closed (SLC). For analog points , the alarm status may have an identifier such as HIGH, LOW, or RATE. CRT Display Service The CRT screen is divided by software into five display areas , as shown in fig- ures 7 and 8. Area 1 contains 12 lines reserved for critical change-of-state conditions. As these conditions occur, the processor enters the data in this area and denotes recent entries with a flashing caret (<) to the right of the data. The user may acknowledge the event by pressing the special ACK key on the keyboard, and the caret will disappear. If the event is an alarm condition, a horn may sound, which is silenced by pressing the SIL key. Since the CRT can display only 12 of these lines at a time, software provision has been made to store remaining alarms in a temporary buffer until CRT space becomes available. In this case, the cursor (*) located to the left of the events will blink. The dis- play can be edited by positioning the cursor to any point with the UP and DOWN keys, and deleting the line with the DEL key. Waiting lines will automatically appear at the bottom of the display area. For protection, it is impossible to delete lines if unacknowledged events are present. Alarms are displayed in reverse video format (black letters on a white background) for easy identification. Area 2 is reserved for user communica- tion with the computer. Keyboard inputs are echoed in this area, which is also used by the processor to prompt for data entry. All invalid input is ignored by the program. User commands consist of three-character mnemonics , some of which are entered by pressing special keys. 15 Area 1 Area 2 Area 3 Critical alarm Displays up to 12 alarms and return to normal conditions simultaneously. Alarms are displayed in reverse video format Operator data request and/or reply, keyboard input echo Continuous status monitoring area Up to 6 analog or binary points ma be displayed and continuously update Area 4 Date Time Sequencing Displays sequence numbers currently in operation Area 5 FIGURE 7. - CRT display areas. FIGURE 8. - CRT data display. 16 Area 3 contains six lines reserved for monitoring continuous status. Any point chosen for display in this area will be continuously updated with current analog value or binary status. Area 4 is serviced by a special program to display the current time and date. These are set by keyboard commands. Area 5 is reserved for event-sequencing activity. Any sequence currently in operation will be displayed in this area; also, interrupted sequences sorted in order of priority will be noted. Event Sequencing The event-sequencing software allows the user to program a series of events with associated time delays. These se- quences may be started either manually (with the ESQ command) or automatically. Automatic sequencing is accomplished by setting a software trigger to initiate the sequence, A trigger is a specified condition for a point; when the point changes status to this condition, the corresponding sequence is initiated by the processor. Changes of state permit- ted for triggering include normal, alarm, high alarm, low alarm, mode 1 (on) , mode 2 (off), and communication failure. In mine situations, event sequencing has been used to restart fans after power bumps and to control LED indicators rep- resenting alarm conditions. The sequencing software contains 255 sequence processing units (SPU's), Each^ SPU has the following structure: Header (contains SPU number, prior- ity, and hold status). Event 1. Event 2, Event 3, Link, pointer (points to another SPU). Up to eight SPU's can be any one time; when more been activated (queued) , and performed according ority, SPU's can be length by using the link to another SPU. in operation at than eight have they are sorted to their pri- chained to any pointer to point A sequence event can be one of three types: a test, a command, or a null event, A test event within a sequence may be applied to any point in the sys- tem and is used to direct the flow of the sequence. Conditions that can be tested include normal, alarm, communica- tion failure, and less than, equal to, or greater than a test value. Condition- al jumps or calls may be chosen as a re- sponse to the test result, A jump di- verts the sequence to another SPU if the test condition is false, A call performs another sequence as a subroutine when the test condition is true. Call depth is limited to four calls within prior calls. Commands in a sequence behave in the same manner as operator commands entered through the keyboard. Although any type of accessor may be tested, only commanda- ble accessors such as the B2, B25, and B26 types may be commanded. Time delays up to 255 s may be Included with a com- mand event. A null event produces no action except continuation of the sequence during pro- cessing. Null events are desirable be- cause of programming considerations. In area 5 of the CRT display are eight reserved lines, which correspond to eight activity nodes present for sequencing. As a sequence is queued, it appears in this area in the following form: 17 start SPU# * current SPU# * current event#. When all eight lines are filled with operating sequences, new sequences will be held until an activity node becomes free. A higher priority sequence will temporarily interrupt a lower priority sequence when all nodes are in use. INSTALLATION As part of the installation process, planning must take place to decide on sensor locations and which fans to moni- tor and control. The actual installation of the system in a mine typically con- sists of stringing the cable; installing accessors, monitors, and protection de- vices; and installing the main processor and associated surface equipment. Elec- trical checkout of the cable is necessary to ensure continuity and separation of the conductors prior to making final con- nections. Care must also be taken to ensure that the accessor trunk shield is tied to ground potential at only one place, usually at the central processor. Failure to do so may result in destruc- tive ground-loop currents. Cable should be placed along the mine back or rib in such a way as to avoid snagging by mine equipment. It is pref- erable not to run cable next to power or feeder cables in order to avoid stray electrical interference. Supporting strength of the cable and cable insula- tion type are determined by the particu- lar application. Since accessors are de- signed to function within 33 pet of 19 V dc, gauge of the power wires in the cable should be chosen to minimize voltage loss due to impedance. The cable supplied by Conspec uses 14-AWG power wires and indi- vidually shielded 18-AWG data wires in an overall shield with a common drain. This cable was found to be adequate in runs up to 3 km from the accessor trunk. Voltage boosters may be used to compensate for voltage loss due to longer runs. Accessors should be installed within proper distance limits to their field devices. Both accessors and field de- vices should be placed in protected areas to minimize accidental damage from per- sonnel and equipment. Accessors used by the Bureau were housed in waterproof metal enclosures; power and communication wires entered through military specifica- tion (MS) type connectors. Lightning protection devices should be installed where cable enters or exits mine buildings, shafts, or portals. Both primary and secondary protection are sug- gested by the manufacturer. Basic surface equipment consists of a central processor, printer(s), battery backup unit, and an accessor communica- tion trunk. Voltage regulation, noise suppression, or power conditioning de- vices may be required if voltage spikes are present on the 110-V ac power input to the processor. A hookup block diagram of the surface equipment is shown in figure 9. After connecting the accessor cable to the communication trunk, voltage may be measured at each accessor to check splice connections and also to ensure that prop- er operation voltage is present. At this point, an accessor check diagnostic can be used to check proper operation of each accessor before starting the main program. Once in the main program, system troubleshooting is simplified by using alarm states to diagnose problems. As an example, the Bureau often uses Bl-type accessors to monitor the power and sensor line condition of continuous radiation monitors. Low alarm limits are set for a value significantly below background count. Power failure to a monitor is then an alarm condition; a low alarm without a corresponding power-fail alarm may indicate an electronic malfunction in the monitor. 18 Battery backup 110 V ac ^ Voltage sensor and time delay + 12 V dc "T ^Communication trunk Inverter 110 V ac Spike protection 110 V ac Power supply To acce ssors + 24 Vdc Data -^ > Surge protection + 24 V dc Data I LL + 24 V dc Line driver card 110 Vac Printer Data Processor Data FIGURE 9. - Block diagram of surface equipment hookups. Communication failure alarms are also diagnostic in nature. They may be. caused by cable incontinuity , improper voltage to accessor, or accessor malfunction. Cable incontinuity would cause a C.FAIL . alarm to be generated for all accessors downstream. This narrows the fault to the area between two accessors: the last with communication and Low voltage commonly types of accessors (Bl may suspect recurring one accessor to be due repeated address or a malfunction. the first without. affects certain type) first. One C.FAIL alarms on to an accidentally possible accessor SYSTEM USE After a final checkout of both surface and underground connections, the user may start the system, enter and begin operation. the data base. 19 STARTUP PROCEDURE The following step-by-step procedure assvimes all connections have been proper- ly made. 1 . Ensure that power is on to terminal and printer(s) . 2. Turn on disk drive, insert system disk, and close drive door, 3. "Cold boot" the system into the CP/M mode by performing the following steps: a. Push the reset button (rear of terminal) . b. Type the spacebar to obtain the CRT message MPS-92 > c. Type the letter F. CP/M will now be loaded from the disk into RAM. After loading is complete, the CRT displays >FQCPM VI. 1 A> 5. After the main program is loaded, an initialized date and time appear on the CRT in addition to the message READ STATUS FRM DISK OPTION (Y OR N) X (flashing) On the first powerup after installation, probably no status information will have been stored on disk. In this case, re- spond "N" and press the return key. Sta- tus, or system configuration, must then be entered through the keyboard into mem- ory before it can be saved on disk. If status has previously been saved, respond "Y" to the prompt before pressing the re- turn key. This causes all system status to be loaded. From this point onward, all user com- mands consist of three-character mnemon- ics typed on the keyboard and followed by the return key. After a command is en- tered, the computer will prompt for further data. 6. After the disk drive stops click- ing, remove the disk, and turn off the drive. An access code must now be en- tered in order to communicate further with the computer. Two access codes are available , which permit different levels of entry: lower (operator) and higher (supervisor) , The A> is known as the A prompt ("A" cor- responds to the disk drive designation) . The computer is now waiting for further user input. The user can now either per- form CP/M functions or enter into the main program mode as shown below. 4. To enter the main program mode, type SUBMIT S and press the return key. This will cause the main program to be loaded, a process which takes about 1 min. During this time, the CRT will display files as they are being loaded. The lower level code allows the user to perform housekeeping functions oriented to system maintenance. These include editing the CRT display, editing the scan, commanding controllable points, making temporary changes in parameters, and requesting certain print routines. The supervisor code contains the opera- tor commands as a subset, and also allows this user to enter and delete points, control disk input and output , set up shift reports, program event sequences, and perform print routines. 20 After entry of the access code, an "ACCESS ALLOWED" message on the CRT noti- fies the user to proceed. 7. Set the time with the STT command. Present time is entered in 24-h format. 8. Set the date with the STD command. The new date and time will now be printed on the printer. DATA ENTRY The data base, or status, consists of all point parameters that may be saved on disk. This includes point numbers, ad- dresses, accessor trunk number, etc., as well as sequencing programs and times for shift report or trend log generation. These data are initially entered by the user through the keyboard with data entry commands such as NEW. The NEW command is used to enter specific accessor informa- tion such as point number, accessor type, address, trunk number, announcement op- tions, and other parameters. Parameters that allow conversion of analog data to engineering units and set alarm limits are also entered at this time. These parameters may be updated at any time with the CAP command. With this command, old values are displayed while the computer waits for new input. Values that the user does not wish to change are retained by pressing the SKIP key. Values for correction factor (CF) and offset (OFS) are actually entered into a memory reference table. These values may be referenced by more than one accessor. Up to 255 different CF and OFS factors may be stored in the table. The CFI and OFS commands are used to enter values into the reference table. A data entry format imist be observed. The format for correction factor (CFI command) is M*X.XX E SX, where M = multiplier (1, 2, or 4), X.XX = value between 0.00 and 2.55, E = 10 (implied), to be raised to the power of SX, and SX = sign and exponent (-7 to +7). The offset entry format (OFS command) is S X.XXXX E SX, where S = sign (+ or -) , X.XXXX = value between 0.0000 and 7.9999, E = 10 (implied), raised to the power of SX, and SX = sign and exponent (-7 to +7). After data entry is completed, the DSS and PCO commands may be used to verify proper entries. Each accessor must be entered in the scan with the EDS command before the processor will initiate comr- munication. Points can also be removed from the scan with this command for main- tenance or other purposes. OPERATION Valid user commands are given in ta- ble 3, An (s) next to the command de- notes it as supervisor-level only, and a (k) signifies that a special key also ex- ists for that command. 21 TABLE 3. - System commands sorted by function Description Command' Function Print routines: Trend log. . . . Accessor scan list. Descriptor list... Shift report Correction factor and offset table. Sequence program- ming units. Sequence triggers. Alarm summary Time and date, Commandable points: Binary point (B2, B22, B25 accessors) . LTT, TREND HDG(k) ACC. DSS, TSR(s), SPN(s), REQ. PCO(s) PSQ(s) STP(s) ALS, ALARM SUMMARY (k). TIME AND DATE(k). COC, COMM BINARY (k). Used to enter point assignment and time period for trend log generation. Up to 10 analog points are permitted, and time per- iod is variable from 1 to 99 min. The TREND HDG key will print a heading for the log. Produces printout of the scan list sorted by address and trunk number. This indicates which accessors are enabled in the scan. Prints point numbers, addresses, descrip- tors, and other data. Generates printouts of averaged values per point for up to 30 points. TSR is used to set printout times from 00 to 23 h (99 gen- erates a report each hour) . SPN assigns points to the report; REQ requests current shift report without reset of count or average. Prints desired range of correction factors and offsets in both machine and floating- point format. Prints desired range of SPU's. Prints sequence triggers by point number. Prints current alarms by point number and identifies alarm condition. Prints current time and date. Used to execute a mode change command on a binary point. A CRT and printer message will indicate result. Analog point (B26 accessor). CPA, COMM ANALOG(k). Changes output position of commandable ana- log point. A CRT and printer message will indicate result. ^A (k) next to a command signifies that it is a special key function. An (s) de- notes it as supervisor level only. 22 TABLE 3. - System commands sorted by funbtion — Continued Description Command ' Function Status file editing: Descriptor change. DSE Allows descriptor change of any point. New descriptor must contain 18 characters (blanks are permitted). Analog parameter change. CAP Allows change of alarm limits , correction factor and offset reference numbers, units code, and other parameters for analog points. Correction factor CFI Enters correction factor into reference ta- entry and change. ble. Only properly formatted correction factors are accepted. Offset entry and change. OFS Enters offset into reference table. Only properly formatted offsets are accepted. New accessor data NEW(s) Enters accessor data into memory. entry. - Edit the scan EDS(s) Enables or disables accessors from the scan. Delete a point. . . . KIL(s) Removes a point from memory. Change access codes. EAC(s) Changes senior and junior access codes. CRT display editing: Auto screen roll ROL Automatically acknowledges and deletes old events from CRT alarm and event area to and acknowledge. make room for display of new data. Set time and date. STT, Used to enter time and date in numerical STD. format . The STD command generates a print- out after date entry. Immediate status ISR, Displays immediate status of any point at request. STATUS (k). the time command is issued. This display ' is not updated. Clear CRT screen. . CRT Clears CRT screen. Only updated data will reappear. Continuous status CSl to C26 Enters and deletes points in status display monitoring. area on lower part of CRT. Disk status: Save status on SVD(s) Saves current status on nonvolatile disk disk. wr*A^\Vir/ * ••• •• • • • •• memory . Read status from RDS(s) Loads status from disk into memory. disk. j.*-fc-» i-f\*<^/9mm9 mm m •• •• Format a disk FMT(s) Formats a new disk to be compatible with system. 'A (k) next to a command signifies notes it as supervisor level only. that it is a special key function. An (s) de- 23 URANIUM MINING APPLICATIONS The computerized system investigated offers many advantages to the uranium mining industry, particularly in the use of its monitoring and control capabili- ties. The system requires only a four- wire cable between the main processor and the accessors to provide 24-V dc power and communication. This cable may be wired in parallel, series, or branched to allow for accessor installation over dis- tances of up to 3 km from the central processor. Longer distances may be achieved through the use of voltage boosters and modems. Up to 128 accessors may be used per trunk line, and up to four of these lines are supported by hardware and software, for a total capacity of 512 accessors. These acces- sors can be interfaced to most stationary mine equipment for monitoring or control, including fans , pumps , radiation detec- tors, air doors, and anemometers. The system's monitoring capabilities may be used to keep records , initiate command sequences, and assist in trouble- shooting the system and its interfaces. RECORDS Recordkeeping is automatic for all changes of state or alarm occurrences. The operator is notified of these occur- rences at the console so that remedial action can be taken if necessary. This can be applied to continuous radiation monitoring as well as to keep track of air door positions or the operational status of fans or other motors. In radi- ation monitoring, a rate alarm may be set to warn of rapidly changing conditions before critical exposure levels are reached. Shift reports may be used as an aid in figuring average working level exposure in monitored areas . Trend logs may be used to study radiation variation in connection with mining activity or environmental changes . Studies such as these may improve ventilation effec- tiveness and thereby reduce ventilation costs. SEQUENCES Command sequences can be constructed for either manual or automatic operation. This feature may be used to turn on, or off,- a number of fans from the console in a predetermined sequence with time delays between steps. Status monitoring then gives feedback to inform the operator of command execution and if indeed the fans went to the commanded state. Anemometers interfaced to the system would give further verification of ventilation flow. In monitoring mine power with the system, the above sequence could be set to auto- matically start fans after a power out- age. Other sequence applications include warning personnel of imminent fan or motor startups or high radiation levels , and controlling fans based on radiation readings . Troubleshooting the system hardware (cables, accessors, and field devices) is aided by using the system's monitoring capabilities. Certain types of alarms may be used to diagnose hardware problems and to narrow down their locations. Basic hardware problems that will be de- tected by the system include broken trunk line, broken sensor line between accessor and field device, power failure for field devices, and certain electronic malfunc- tions in field devices such as radiation monitors . CONCLUSIONS With continually changing radon daugh- ter concentrations present in underground uranixim mines, minimizing worker exposure can be difficult. The system described in this report has the capability to con- tinuously monitor critical situations such as fan operation and radon daughter concentrations and to alert the ventila- tion engineer when excessive measurements are present. It also has the capability to control ventilation, sound underground warnings, and automatically restart fans after power failures. Recordkeeping fea- tures of the system will help the venti- lation engineer to control radiation haz- ards and to predict where future problems may occur. 24 REFERENCES 1. Archer, V. E. Statement on the Ra- don Daughter Standard and Changes Pro- posed by MESA. Testimony before the Fed- eral Metal/Nonmetal Mine Safety Advisory Committee, Seattle, WA, Oct. 26-28, 1976, 8 pp.; available upon request from Spo- kane Res. Cent., BuMines, Spokane, WA. 6. Franklin, J. C. Control of Radia- tion Hazards in Underground Uranium Mines. Paper in Proc. Radiation Hazards in Mining: Control, Measurement, and Medical Aspects, Oct. 4-9, 1981, Golden, CO. Soc. Min. Eng. AIME, 1981, pp. 441- 446. 2. Bates, R. C. Ventilation Cost Im- pact of Reduced Radon Daughter Working Levels. Paper in Proc. Radiation Hazards in Mining: Control, Measurement, and Medical Aspects, Oct. 4-9, 1981, Golden, CO. Soc. Min. Eng. AIME, 1981, pp. 1066- 1070. 3. Franklin, J. C, T. 0. Meyer, R. W. McKibbin, and J. C. Kerkering. A Contin- uous Radon Survey in an Active Uranium Mine. Min. Eng. (N.Y.), v. 30, No. 6, June 1978, pp. 647-649. 4. Musulin, C. S., J. C. Franklin, and F. A. Roberts. Effects of a Fan Shutdown on Radon Concentration in a Positive Pressure Ventilated Mine. BuMines RI 8738, 1982, 10 pp. 5. Musulin, C. S., J. C. Franklin, and V. W. Thomas. Effects of the Diurnal Cy- cle and Fan Shutdowns on Radon Concentra- tion in an Experimental Uranium Mine. BuMines RI 8663, 1982, 13 pp. 7. Droullard, R. F., and R. F. Holub. Continuous Working-Level Measurements Us- ing Alpha or Beta Detectors. BuMines RI 8237, 1977, 14 pp. 8. Shaw, D. M. , and J. C. Franklin. Continuous Area Monitoring and Alarm Sys- tem. Eng. and Min. J,, v. 183, No. 5, May 1982, pp. 84-90. 9. Conspec Controls, Ltd. (Downs- view, Ontario, Canada). Senturion-200 Hardware and Software Reference Manuals, 1982 versions. 10. Zaks, R. The CP/M Handbook with MP/M. Sybex, Inc., Berkeley, CA, 1980, 321 pp. 11. Franklin, J. C, R. J. Zawadski, T. 0. Meyer, and A. L. Hill. Data- Acquistion System for Radon Monitoring. BuMines RI 8100, 1976, 19 pp. 25 APPENDIX. —ANALOG ACCESSOR CALCULATIONS Data returned from analog accessors, depending on the accessor type, contain either one or two bytes of digitized ana- log data. The computer processes these data for alarms and uses a single- precision math routine to convert to en- gineering units for printout and display. Initially, the user is required to calcu- late and enter parameters that are used by the system to determine alarms and to convert accessor values to engineering units. These parameters may be saved as status on disk and read into memory upon later startups. The basic equation used by the processor is Correction factor and offset are calcu- lated from these values as follows: FP = R * CF + OFS, (A-1) where FP = floating point value for display, R = accessor value, CF = correction factor, and OFS = offset. The accessor value is the returned data from eight-bit accessors or the eight most significant bits from pulse- integrating (PI) accessors. Because PI accessors have additional hardware fac- tors involved (selectable count period and prescaler) , their calculations are slightly different and will be covered later. EIGHT-BIT ACCESSORS To calculate the correction factor and offset for A5 or A8 accessors, the values to be displayed at the minimum and maxi- mum imputs must be known. For the A5 accessor, this represents the values at V dc (minimum input) and 5 V dc (maximum input). For the A8 accessor, this repre- sents the values at ohms resistance of the remote potentiometric sensor (minimum input) and 2,000 to 10,000 ohms full- scale resistance of the remote potentio- metric sensor (maximum input). and CF = OFS = Vmin, Vmax - Vmin 255 (A-2) (A-3) where OFS = offset, CF = correction factor, Vmin = value to be displayed at minimum input , and Vmax = value to be displayed at maximum input. Alarm limits are calculated in machine units for data entry reasons. These can be obtained by substituting desired alarm limit values (for FP) into equations A-4 and A-5 to calculate for the accessor value (R) as shown below: FP(L) = R(L) * CF + OFS, (A-4) and FP(H) = R(H) * CF + OFS, (A-5) where FP(L) = floating point low alarm value , FP(H) = floating point high alarm value , R(L) = low alarm limit in ma- chine units, and R(H) = high alarm limit in ma- chine units. Values obtained for alarm limits , R(L) and R(H) , are rounded to the nearest whole number for machine entry. An exam- ple analog calculation is shown below, A J-Tec anemometer is to be used to measure air velocity in a drift. Since the J-Tec has an analog voltage output , it will be used with an A5 accessor. The following information is known: 26 1. J-Tec VA-215 anemometer output is from to 5 V dc, corresponding to air velocity from to 1,500 ft/min. 2. The desired alarm limits are Low limit = 100 ft/min. High limit = 1,000 ft/min. Determine (1) CF and OFS and (2) alarm limits for machine entry (R values): 1. CF and OFS: From equation A-3: ^ Vmax - Vmin ^ 1,500 - 255 255 = 5.88. From equation A-2: OFS = Vmin = 0.00. 2. Alarm limits: Low alarm (100 ft/min) From equation A-4: 100 = R(L) * 5.88 + 0; R(L) = 17. High alarm (1,000 ft/min) From equation A-5: 1,000 = R(H) * 5.88 + 0; R(H) = 170. PULSE-INTEGRATING ACCESSORS The following discussion pertains to a PI accessor interfaced to a continuous radiation monitor such as a radon or working level monitor. The continuous radiation monitor outputs random electrical pulses corresponding to radiation input. PI ac- cessors accumulate a count of these pulses for a preset time period. Accu- mulated pulses are converted to radiation concentrations such as picocuries per liter or working levels by the equation RC = ^^-^^ * DF C * DF B * DF (A-6) where RC = radiation concentration, C = gross accumulated pulses , B = background (per period T) , T = present count period, and DF = calibration factor. The PI accessor divides incoming pulses by a prescaler value and accumulates the result for a period of time (T) . At the end of T, this result (the accessor val- ue) is latched and supplied to the pro- cessor upon interrogation. At the end of each T, the old value is replaced by a new one. Prescaler Value The relationship between accessor value and actual count is where and R = C/P, R = accessor value, C = count from radiation monitor , P = prescaler value. (A-7) Although the maximum accessor value is software-limited to 37,767, the optimum range of R in consideration of processing speed is 256 < R < 512. (A-8) 27 Therefore, under normal radiation condi- tions, the accessor will be set up so that the prescaler value is in the range 256 < C/P <> 512 (desirable condition). (A-9) Furthermore, the prescaler value must be an integer between 2 and 255, inclusive. This value is set as a binary number on dipswitch S22. Correction Factor, Offset, and Alarm Limits Example PI Calculation In this example, a calibrated working level monitor has been installed in a mine heading. The desired sample time is 5 min. The following information is known: 1. Average background count in the heading is 5,500 counts per 5 min, 2. The detector calibration factor (DF) is 6.7 E-4 WL-min per count. 3. The desired alarm limits are The CF and OFS values are used by the processor to convert the R value to radi- ation concentration (RC). Equation A-1 is used in this operation, and the float- ing point value to be found is RC: RC = R * CF + OFS, where RC = radiation concentration (floating point value), R = accessor value, CF = correction factor, and OFS = offset (may be positive or negative) . By substituting with equations A-6 and A-7 and rearranging terms , a similar form can be obtained: RC = R * (P * DF) (B * DF) (A-10) Therefore, for the continuous radiation monitors , CF = P * DF and OFS = - (B * DF) (A-11) (A-12) The background (B) and count (C) terms in the above equations are averaged val- ues obtained during monitor calibration. Low limit = 2,750 counts per 5 min (one-half of background). High limit =1.0 WL. Determine (1) optimum prescaler value, (2) CF and OFS, and (3) alarm limits for machine entry (R values): 1. Optimum prescaler value: The "normal" expected radiation concentration ranges up to 1 WL; therefore, count at 1 WL is found from equation A-6: 1 WL - ^'= - l'^""'' * (6.7 E-"). C(l WL) = 12,962 counts. Prescaler range from equation A-8 is 12 962 256 < ^ ;^°^ < 512; therefore, 25 < P < 50. A moderate value, P = 40, is then chosen. 2. CF and OFS: From equation A-11: 40 * (6.7 E-4) CF = = 5.36 E-5. 28 From equation A-12: OFS = - 5,500* (6.7 E'M = - 7.37 E-^ 3. Alarm limits: Low alarm (one-half of background = 2,750 counts) From equation A-7: R(L) = 2,750/40 = 69. High alarm (1.0 WL) From equation A-1: 1.0 WL = R(H) * (5.36 E'^) - (7.37 E-1) , R(H) = 324. INT.-BU.OF MINES,PGH.,PA. 27 566 . » * A -^fA'„ \,^^ /^^ \/ ;^^o %,^^ - ,-v V' 6 O" • ^"'-» "^ V .... ♦^^ *-.# 0^ ol* • / 1 • - V .»* A \.** •• v^ .*l.^'* . » • ■ ^b. 'o . , • A " '°- ,4.*^ .^^^ V * * / .*l-^% '°o .-Jv^ iPvV >M/}^M' a"^ -^ "•' *..<^ •• '^- " "^^ f ^ " "^^^d^ V, \^ .. 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