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Model 78 and 78-1

Technical Manual

Section 4

Ludlum Measurements, Inc.

Page 4-2

March 2021

Low Battery Icon

: indicates that the batteries have decreased to the minimum operating

voltage of 2.2 ±0.1 Vdc

COUNTING

: appears upon power-up, but not implemented

Front Panel Controls

ON/OFF Switch

: a two-position toggle switch that applies power to the instrument.

AUD ON/OFF Switch

: The clicks-per-event audio may be silenced or enabled via this front-

panel toggle switch. The audible alarm is independent of the

AUD ON

OFF

switch and will

override the audible clicks-per-event. An audible alarm can only be silenced by toggling the

RESET

switch.

mR/hr - R/hr Select Switch

: a protected toggle switch that toggles between mR/hr and R/hr

ranges

F/S (Fast/Slow) Response Switch

: a two-position toggle switch that selects fast or slow

counting response time

Variable Response

: dependant on the number of counts present; typically

4 to 25 seconds for

FAST

, and 4 to 60 seconds for

SLOW

Fixed Response

: The

FAST

response position is programmable from 1-199

seconds. The

SLOW

response position is approximately five times slower

than the

FAST

. For MDA-type measurements, the fixed response mode is

recommended

BKLITE (LCD Backlight) /RESET

: A momentary switch, which when pressed to the

BKLITE

position illuminates the LCD for a pre-programmed time. The backlight "

" time can be

selected from between 5 and 240 seconds during parameter setup. In the non-alarm
condition, pressing the momentary switch to

RESET

resets the ratemeter display to the

minimum display readout. In an alarm condition, pressing

RESET

will silence the audible

alarm. Pressing

RESET

a second time will reset the ratemeter

ALARM

and/or

ALERT

condition.

Main Board Controls

Note:

To access the internal circuit boards, unlatch the latches at each end of the
Model 78. Carefully separate the top chassis from the bottom cover (referred

to as a "can"). The can has the audio speaker (unimorph) with a two-
conductor cable attached to the main board. The audio plug may be

disconnected during the internal control adjustments.

Содержание 299335

Страница 1: ...LUDLUM MODEL 78 AND 78 1 DIGITAL ANALOG STRETCH SCOPE March 2021 Serial Number 299335 and Succeeding Serial Numbers ...

Страница 2: ...LUDLUM MODEL 78 AND 78 1 DIGITAL ANALOG STRETCH SCOPE March 2021 Serial Number 299335 and Succeeding Serial Numbers ...

Страница 3: ...n any implied warranty of merchantability or fitness which extend beyond the description of the face there of If the product does not perform as warranted herein purchaser s sole remedy shall be repair or replacement at the option of Ludlum Measurements In no event will Ludlum Measurements be liable for damages lost revenue lost wages or any other incidental or consequential damages arising from t...

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Страница 8: ...ont Panel Controls 4 2 Main Board Controls 4 2 Cal Switch Board Controls 4 3 Safety Considerations 5 Environmental Conditions for Normal Use 5 1 Warning Markings and Symbols 5 1 Cleaning and Maintenance Precautions 5 2 Maintenance 6 Recalibration 6 1 Batteries 6 2 Technical Theory of Operation 7 Detector Input Amplifier 7 1 Discriminator 7 1 Low Voltage Supply 7 1 High Voltage Supply 7 2 Detector ...

Страница 9: ...and Variables 8 2 Loading Default Parameters 8 4 Calibration 8 4 General Detector Setup Information 8 5 Exposure Rate Calibration 8 5 Detector Overload OVL Calibration 8 6 Recycling 9 Parts List 10 Model 78 Digital Analog Stretch Scope 10 1 Main Circuit Board Drawing 272 x 591 10 1 Cal Switch Board Drawing 272 352 10 3 Display Board Drawing 408 259 10 4 Chassis Wiring Diagram Drawing 272 596 10 5 ...

Страница 10: ...e on time programmable fixed or variable response time and a count overflow visual alarm Warning There is a reduced response in pulsed fields due to the detector dead time The Model 78 incorporates independent adjustable alarms for both detectors There are two alarm indications The first level alarm is indicated by display of ALERT on the LCD The second level alarm is indicated by display of ALARM...

Страница 11: ...nstrument is calibrated to a specific detector s and is therefore not interchangeable To return an instrument for repair or calibration provide sufficient packing material to prevent damage during shipment Also provide appropriate warning labels to ensure careful handling Include detector s and related cable s for calibration Every returned instrument must be accompanied by an Instrument Return Fo...

Страница 12: ... Turn the ON OFF switch to the ON position The display goes through an initialization sequence showing all 8s with decimal points Check on all segments to ensure they are on as illustrated The LCD then shows the firmware number in the format P XX YY The XX is the firmware number and the YY is the firmware version The following figure is for example only to illustrate location of display Note The M...

Страница 13: ...e alarm conditions If an alarm condition is not present depressing RESET the first time will reset the alert condition and zero the ratemeter Position a check source to produce a reading of 0 5 to 2 0 mR hr 0 005 to 0 02 mSv h while observing the ratemeter fluctuations select between the fast and slow response time FAST SLOW positions to observe different variations in the display The SLOW positio...

Страница 14: ...er response All stated times correspond to a range of 10 to 90 of the final reading Factory default is variable so that the instrument will automatically adjust the response time to the best setting for the current count rate Variable Response dependent on the number of counts present typically 4 to 25 seconds for FAST and 4 to 60 seconds for SLOW Fixed Response The FAST response position is progr...

Страница 15: ...dle current drain approximately 35 mA backlight off minimum battery voltage 2 2 0 1 Vdc BATTERY DEPENDENCE Meter readings vary by less than 3 from fully charged batteries until the battery symbol appears indicating the need for recharge or replacement BATTERY LIFE approximately 250 hours for alkaline batteries battery failure indicated on display SIZE 12 2 x 10 9 x 105 9 cm retracted 377 2 cm full...

Страница 16: ...ressing RESET will acknowledge the audible ratemeter alarm Depressing RESET a second time will reset the ratemeter reading and ratemeter alarm ALERT ratemeter count has increased above the preset alert threshold To reset an ALERT condition depress RESET once if in the non alarm condition and twice if in an ALARM condition The first depression in the alarm condition acknowledges the audible alarm T...

Страница 17: ...or FAST and 4 to 60 seconds for SLOW Fixed Response The FAST response position is programmable from 1 199 seconds The SLOW response position is approximately five times slower than the FAST For MDA type measurements the fixed response mode is recommended BKLITE LCD Backlight RESET A momentary switch which when pressed to the BKLITE position illuminates the LCD for a pre programmed time The backlig...

Страница 18: ...e latches at both ends of the instrument and remove the electronics DISC Discriminator a multi turn potentiometer approximately 20 revolutions used to vary the detector pulse counting threshold from 2 to 100 mV A Ludlum Model 500 Pulser or equivalent should be used in checking or adjusting the pulse discrimination parameter Note When making adjustments to the HV potentiometer make note of the foll...

Страница 19: ... and 40 microamperes corresponding to the specific detector saturation point The Cal Switch board also utilizes a 16 position rotary switch FUNCTION to select the 16 setup parameters Refer to schematics and component layout drawing near the end of the manual All of the setup parameters are stored in the non volatile EEPROM which will retain data even after the Model 78 batteries are removed Changi...

Страница 20: ...4 Occurs when conductive pollution or dry nonconductive pollution becomes conductive due to condensation This is typical of industrial or construction sites Environmental Rating IP52 Warning Markings and Symbols Caution The operator or responsible body is cautioned that the protection provided by the equipment may be impaired if the equipment is used in a manner not specified by Ludlum Measurement...

Страница 21: ...e the batteries 2 Allow the instrument to sit for one minute before accessing any internal components The crossed out wheelie bin symbol notifies the consumer that the product is not to be mixed with unsorted municipal waste when discarding each material must be separated The symbol is placed on the front panel See Section 9 Recycling for further information The CE mark is used to identify this in...

Страница 22: ...aning or accessing internal components for maintenance Recalibration Recalibration should be accomplished after any maintenance or adjustment of any kind has been performed on the instrument Battery replacements are not considered to be maintenance and do not normally require the instrument to be recalibrated Note Ludlum Measurements Inc recommends recalibration at intervals no greater than one ye...

Страница 23: ...osion at least every three months If the instrument has been exposed to a very dusty or corrosive atmosphere more frequent battery servicing should be used Note Never store the instrument over 30 days without removing the batteries Although this instrument will operate at very high ambient temperatures battery seal failure can occur at temperatures as low as 37 C 100 F ...

Страница 24: ... pulses from amplifier U021 are coupled to pin 2 of U011 comparator The discrimination level is set by the DISC control connected to pin 3 of U011 As the positive pulses at pin 2 of U011 increase above DISC reference at pin 3 pin 1 goes low producing a low pulse Pin 1 of U011 is normally held high 5 volts by R014 The low pulse from pin 1 of U021 is coupled to univibrator U001 U001 shapes and fixes...

Страница 25: ...drop is developed across R031 and sensed by comparator pins 5 6 and 7 of U131 as detector current increases When the voltage at pin 5 of U012 goes below pin 6 pin 7 goes low signaling U111 µP to send the OVERLOAD alarm to the LCD OVL control on Cal Switch Board provides adjustment for the overload set point Microprocessor µP U111 controls all of the data control inputs and display information The ...

Страница 26: ...ransfer the data to the LCD drivers The backplane BP signal from U211 provides the reference signal approximately 125 Hz at 5 Vdc to the LCD DSP1 BP connection When a segment is illuminated the signal to that segment will be out of phase with the BP signal If the segment is OFF the signal will be in phase with the BP signal Backlight Drive Depressing the BKLITE button instructs the µP to set the B...

Страница 27: ...e LCD associated with a particular parameter Once the desired data is entered depress the ENTER button The LCD characters should stop flashing and the new parameter data should display To read pre programmed setup parameters switch the FUNCTION switch to position A and select the pre programmed detector setup number using the parameter change procedure above Once the detector setup number is enter...

Страница 28: ...system dead time POSITION 2 CALIBRATION CONSTANT allows changing the calibration constant for the current detector setup The calibration constant CC adjusts from 0 001 to 280 X 109 The calibration constant converts counts time base to units time base POSITION 3 SERIES CONSTANT adjusts the calibration of the high range tube typically about 300 Adjustable from 0 to 9999 POSITION 4 NOT USED POSITION ...

Страница 29: ...wer than the fast TC For MDA type measurements the fixed response time mode is recommended POSITION 7 RATEMETER ALARM ALERT allows changing the ratemeter alarm for the current detector setup The units of this alarm are the same as the units for the ratemeter display The fifth push of the left button allows the decimal point to be moved The ratemeter alarm adjusts from 1µR to 999 R hr POSITION 8 NO...

Страница 30: ...LCD Time Off 5 sec Detector 0 Calibration The Model 78 calibration routine consists of entering detector parameters into memory by way of the switch board and adjusting the CAL controls HV1 HV2 DISC and OVL for the specific detector operating requirements The first subsection of calibration will give a general overview of detector setup including the determination of various detector operating vol...

Страница 31: ... with the following values for DT Dead Time Switch Position 1 CC Calibration Constant Switch Position 2 and SC Series Constant Switch Position 3 Note that the SC is left at zero for the lower range tube but is used for the high range tube s calibration For exposure rates mR hr DT 75 x 10 6 CC 645 x 105 SC 0000 R hr DT 40 x 10 6 CC 100 x 104 SC 300 For dose equivalent rates Sv h Firmware 27201n07 µ...

Страница 32: ... pulse output continues to decrease in the saturated field the detector current drain continues to increase This increase in current is detected by a comparator circuit which triggers the OVERLOAD enunciator on the LCD by way of the microprocessor For GM detectors the OVL trip point is adjusted to the point to where the readout no longer increases with increasing radiation intensity In the event t...

Страница 33: ...t simply desires to inform its consumers of the range of recyclable materials present in its products so that the user will have flexibility in following all local and federal laws The following types of recyclable materials are present in Ludlum Measurements Inc electronics products and should be recycled separately The list is not all inclusive nor does it suggest that all materials are present ...

Страница 34: ... 04 5663 C021 100pF 3KV 04 5532 C031 0 0047µF 3KV 04 5547 C032 100pF 3KV 04 5532 C033 0 0047µF 3KV 04 5547 C041 C043 0 0047µF 3KV 04 5547 C101 47µF 10V 04 5666 C121 47µF 10V 04 5666 C122 C123 27pF 100V 04 5658 C131 0 0047µF 3KV 04 5547 C132 C133 0 1µF 50V 04 5663 C134 0 01µF 50V 04 5664 C135 47µF 10V 04 5666 C136 0 01µF 50V 04 5664 C137 47µF 10V 04 5666 C138 100pF 100V 04 5661 C139 0 001µF 100V 04...

Страница 35: ...1 LM358D 06 6312 U231 LT1073CS8 5 05 5852 SOCKET 44P 06 6613 CR021 MMBD7000LT1 07 6355 CR031 GI250 2 07 6266 CR041 CR044 GI250 2 07 6266 CR231 CXSH 4 EB33 07 6358 CR241 MMBD914LT1 07 6353 CR242 CXSH 4 EB33 07 6358 R002 10K 3269X1 103 09 6921 R027 1M 3269X1 105 HV LIMIT 09 6906 R001 100K 1 4W 1 12 7834 R011 R012 10K 1 4 W 1 12 7839 R013 1K 1 4W 1 12 7832 R014 10K 1 4W 1 12 7839 R015 100K 1 4W 1 12 ...

Страница 36: ...0Ohm 1 4W 1 12 7840 R241 2 21K 1 4W 1 12 7835 R242 200Ohm 1 8W 1 12 7846 Y221 6 144 MHZ 2 GND 3 GND 01 5262 L231 100µH CTX100 2 21 9740 T101 4275 083 AUDIO 4275 083 T141 L8050 40 0902 P1 1 640456 2 MTA100 12 13 8061 P2 1 640456 3 MTA100 13 13 8100 P3 640456 6 MTA100 6 13 8095 P4 640456 2 MTA100 2 13 8073 P5 1 640456 2 MTA100 12 13 8061 CLVRLF 18 8771 BOARD Completely Assembled Cal Switch Board 527...

Страница 37: ...7023 R14 1 5K 1 4W 5 10 7065 R15 1K 1 4W 5 10 7009 R16 1M 1 4W 5 10 7028 SW1 3CTH9 PB UP 08 6716 SW2 3CTH9 PB LEFT 08 6716 SW3 3CTH9 PB ENTER 08 6716 SW4 350134GSK FUNCTION 08 6721 P6 640456 5 MTA100x5 13 8057 P7 640456 3 MTA100x3 13 8081 P9 1 640456 0 MTA100x10 13 8066 P10 640456 6 MTA100x6 13 8095 P11 640456 2 MTA100x2 13 8073 P13 640456 2 MTA100x2 13 8073 BOARD Completely Assembled Display Boar...

Страница 38: ... MTA100 6 13 8171 J4 CONN 640442 2 MTA100 2 13 8178 J5 CONN 1 640442 2 MTA100 2 13 8407 J6 CONN 1 640442 5 MTA100 5 13 8140 J7 CONN 640442 3 MTA100 3 13 8512 J8 CONN 640442 8 MTA100 8 13 8184 J9 CONN 1 640442 0 MTA100 10 13 8136 J10 CONN 640442 7 MTA100 13 8171 J11 CONN 640442 2 MTA 100 13 8178 J12 JACK TINI 42A 21 9333 J13 CONN 640440 2 MTA 100 2 13 8202 R1 10M 1 4W 5 10 7031 R2 3 3M 1 4W 5 10 70...

Страница 39: ...arch 2021 Reference Description Part Number BODY DETECTOR 2272 287 W2 RG 174 U 8612 21 9463 BOARD ASSEMBLY TUBE 5272 584 V1 GM TUBE 71210 01 5295 V2 GM TUBE 71616 01 5298 SHLD THOMPSON TUBE 01 5055 W1 COIL CORD 8348 8272 309 LABEL AVERY S1014 03 5352 6 FT SHOULDER STRAP 22 9649 ...

Страница 40: ...cuit Board Drawings 272 x 591 3 sheets Main Circuit Board Component Layout Drawing 272 x 590A Cal Switch Board Drawing 272 352 Cal Switch Board Component Layout Drawing 272 353 Display Board Drawing 408 259 Display Board Component Layout Drawings 408 260 2 sheets Wiring Diagram Drawing 272 596 Section 11 ...

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