Ludlum Measurements 375-9 User manual

LUDLUM MODEL 375-9
DIGITAL WALL-MOUNT AREA MONITOR
WITH MODELS 45-9 & 45-9-1 ION CHAMBERS
July 2016
Serial Number 230666 and Succeeding
Serial Numbers

LUDLUM MODEL 375-9
DIGITAL WALL-MOUNT AREA MONITOR
WITH MODELS 45-9 & 45-9-1 ION CHAMBERS
July 2016
Serial Number 230666 and Succeeding
Serial Numbers

Ludlum Measurements, Inc. July 2016
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Connecting the Detector 2-2
Power Up 2-2
Radiation Units 2-3
Checking Parameters 2-3
Setting Alarm-points 2-4
Operational Check (optional) 2-4
Specifications 3
Instrument Specifications 3-1
Detector Specifications 3-2
Operator Controls and Setup 4
Calibration Controls 4-1
Dipswitch (under calibration cover) 4-1
RS-232 Output 4-2
Demonstration Program 4-3
9-Pin Data Connector 4-4
Common Options and Modifications 5
Time and Date Stamp Option 5-1
Relay Options 5-2
4 to 20 mA Isolated Output Driver Option 5-3
Safety Considerations 6
Environmental Conditions for Normal Use 6-1
Cleaning Instructions and Precautions 6-2
Warning Markings and Symbols 6-2
Replacement of Main Fuse 6-3
Battery Replacement 6-3

Model375-9 TechnicalManual
Ludlum Measurements, Inc. July 2016
Calibration 7
Instrument Calibration Parameters 7-1
Analog Output 7-1
Threshold 7-2
Battery Charge 7-2
Detector Calibration 7-2
Detector Electronics Checkout 7-3
Recycling 8
Parts List 9
Model 375-9 Digital Wall-Mount Area Monitor 9-1
Main Board, Drawing 396 × 608 9-1
Wiring Diagram, Drawing 396 × 869 9-4
Model 45-9 Remote Area Monitor 9-4
Model 45-9-1 Remote Area Monitor 9-4
Remote Electrometer, Drawing 280 × 219 9-4
Drawings and Diagrams 10

Model375-9 TechnicalManual Section1
Ludlum Measurements, Inc. Page 1-1 July 2016
Introduction
he Model 375-9 Digital Wall-Mount Area Monitor is designed for
visibility and ease of use. Featuring a wall-mount chassis, the Model
375-9 has a four-digit LED display that is readable from thirty feet
away. Backlit indicators warn of low radiation alarm (yellow), high
radiation alarm (red), instrument failure (red) and low battery (yellow). A green
status light is a positive indication of instrument operation.
Note:
The Model 375-9 Ethernet (1370-055) option:
The Model 375-9 can also be modified to add a 100BaseT
Ethernet port. This port allows remote display and logging of
the data from the Model 375-9. To do this, special firmware
allows combinations of front-panel buttons to perform
additional functions. For example, press the LOW ALARM
and the CAL CONST buttons to set the unit ID and press the
LOW ALARM and DEADTIME buttons to set the Port
number- 0 to 9999 = port 50000 – 59999. Consult the Ludlum
Model 375 Ethernet manual for further assistance.
Parameters are protected under a calibration cover. Calibration is easily
accomplished by moving the CAL dipswitch to the right, and using the
pushbuttons to increment or decrement the calibration constant, dead time
correction and alarm point parameters. Parameters are stored in non-volatile
memory (retained even with power disconnected).
A five-decade logarithmic analog output is provided. A battery backup provides
48 hours of additional use after the primary power is removed. The
Model 375-9 comes equipped with an external detector, able to detect gamma
radiation. Typical range is from 0.1 mR/hr to 1 R/hr (other ranges available)
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Two common Model 375-9 systems with external detector are:
The Model 375-9 with Model 45-9 Ion Chamber
The Model 375-9 with Model 45-9-1 Ion Chamber Both detectors utilize a
stainless steel pressurized ion chamber with lead shielding for energy
compensation. An energy response curve is provided in the back of this
manual for quick reference.
Detector and electrometer are housed in an aluminum case. The electrometer
converts the detector signal to a pulse train for instrument recognition, and
generates the voltage for the detector anode

Model375-9 TechnicalManual Section2
Ludlum Measurements, Inc. Page 2-1 July 2016
Getting Started
he Model 375-9 Digital Wall-Mount Area Monitor is designed for
ease of use. This section of the manual is designed to help the first-
time user get started. Initial power-up and basic features of the
Model 375-9 will be discussed in this section. Other sections of the
manual provide more detailed information.
Unpacking and Repacking
Remove the calibration certificate and place it in a secure location. Remove
the instrument and ensure that all items listed on the packing list are in the
carton. Check individual item serial numbers and ensure calibration
certificates match between instruments and detectors (if applicable).
To return an instrument for repair or calibration, provide sufficient packing
material to prevent damage during shipment.
Every returned instrument must be accompanied by an Instrument Return
Form, which can downloaded from the Ludlum website at
www.ludlums.com. Find the form by clicking the “Support” tab and
selecting “Repair and Calibration” from the drop-down menu. Then choose
the appropriate Repair and Calibration division where you will find a link to
the form.
Notice!
Volume 49 of the Code of Federal Regulations
(Transportation) applies anytime a person is
transporting or offering for transport, a hazardous
material to, from or through the United States
United States law states that shipping of hazardous
materials/dangerous goods requires that each Hazmat
Employee as defined by 49 CFR 171.8, must receive
training and be tested in accordance with 49 CFR
172.700 – 172.704.
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Model375-9 TechnicalManual Section2
Ludlum Measurements, Inc. Page 2-2 July 2016
Connecting the Detector
The Model 375-9 comes equipped with either a Model 45-9 or 45-9-1 Ion
Chamber (detector). The instrument detector connector is located on the
bottom of the chassis. Use the cable provided to connect the detector to the
Model 375-9.
Power Up
Plug the power cord into a suitable wall (Mains) outlet.
Note:
Model 375-9 units will normally be wired internally for 120
VAC. If requested, the unit may be wired for 220 VAC.
Check the label next to the AC input receptacle to verify the
required input voltage.
If the RS-232 feature is used, plug in a suitably wired 9-pin connector cable.
(See Page 4-4 for the pin assignment of the 9-pin connector.) Turn power
ON with the left side panel switch. Do not turn power OFF unless the unit is
to be removed from service.
Read and then remove the sticker (illustrated to the
left) from the instrument calibration cover.
Checking and setting of the alarm-point(s) is
discussed in detail pages 2-2 and 7-1 of this manual.
Initial power-up will momentarily activate the
internal front panel lights, sound the audio, and
display "8888" on the 4-digit LED display. The
firmware version number (39665Nyy) is then
displayed as "396" and "65yy" (where yy represents
the current version number).
When the instrument has finished measuring background, it will display the
current radiation reading and begin checking for an alarm condition.

Model375-9 TechnicalManual Section2
Ludlum Measurements, Inc. Page 2-3 July 2016
Radiation Units
The Model 375-9 may be calibrated for almost any desired radiation units of
measure. Common units of measure include mR/hr, µR/hr, R/hr, mSv/h,
µSv/h, cps, cpm, and kcpm. In each case, the unit of measure is indicated
underneath the four-digit display. Throughout the rest of this manual, the
notation <units> will be used as a substitute.
Checking Parameters
Check the low alarm point setting by pressing the LOW ALARM button. The
low alarm point will be displayed as long as the button is pressed. The low
alarm point is in units of <units>. The low alarm point can be set from 0.1
<units> to 9999 <units>.
Check the high alarm point setting by pressing the HIGH ALARM button. The
high alarm point will be displayed as long as the button is pressed. The high
alarm point is in units of <units>. The high alarm point can be set from 0.1
<units> to 9999 <units>.
Check the calibration constant by pressing the CAL CONST button. The
calibration constant will be displayed as long as the button is pressed. The
calibration constant is in units of cpm (counts per minute) per <units>. The
calibration constant can be set from 0.1 cpm/<units> to 9999
cpm/<units>.
Check the detector dead time correction by pressing down on the DEAD
TIME button. The dead time correction will be displayed as long as the
button is pressed. The dead time correction is in units of microseconds. The
dead time correction can be set from 0.1 microseconds to 9999 micro-
seconds.
Check the background subtract parameter by simultaneously pressing both
LOW ALARM and HIGH ALARM buttons. This feature allows the user to set a
number to subtract from all measurements. This feature is necessary since
the ion chamber electrometer is normally set to output 400 cpm (6.67 cps) as
the zero reference.

Model375-9 TechnicalManual Section2
Ludlum Measurements, Inc. Page 2-4 July 2016
Setting Alarm-points
The LOW ALARM and HIGH ALARM points can only be changed while the
instrument is in calibration mode. Switch the top dipswitch CAL MODE
(behind the calibration cover) to the right to place the instrument into
calibration mode.
Changing alarm-points is done by holding down the corresponding
parameter key and pressing the up or down arrow buttons. Alarm-points can
be set in the range of 0.1 to 9999. When an alarm-point is changed the
instrument will sound an audible beep to confirm the saving of the
parameter, and will then return to displaying the current radiation level.
Note:
Once the alarm point(s) is set, it is important to remember to
switch the CAL MODE switch back to the left. This action
protects the parameters from inadvertent changes.
Operational Check (optional)
The operational check is an important assurance that the radiation detector
and electronics are working correctly.
Note:
Ludlum Measurements suggests that an operational check be
performed on a regular basis. Local procedures may
supersede.

Model375-9 TechnicalManual Section2
Ludlum Measurements, Inc. Page 2-5 July 2016
For an operational check it is necessary to use a radiation check source (not
included, but available). When not being used, store the check source in a
secure area.
Note:
LMI check sources present very minimal risks and are
therefore unlicensed (Exempt Quantity Sources reference:
10 CFR 30.71 Schedule B). The radioactive element is sealed
(permanently bonded or fixed inside a capsule) so you need
not wash your hands after handling. Radiation exposure
while handling this source is very minimal with no identified
long or short term risks. Although the amount of radiation
given off by exempt sources is so low that it presents no
significant hazard, they should be handled with care and
respect. Time, distance and shielding are the best ways to
control exposure.
1. Taking the source in hand, place it so that it is located on or near
the center (same location each time) of the detector. (For
internal detector models, a metal plate on the bottom of the
chassis identifies the location of the internal detector.) Hold it
there for approximately 5 seconds or until the reading stabilizes.
Take note of the displayed level of radiation.
2. Verify that the reading is within 20% of the last reading
obtained. Remove the source from the detector.
3. If an alarm is activated, ensure that all visual and audible devices
(if applicable) work correctly.

Model375-9 TechnicalManual Section3
Ludlum Measurements, Inc. Page 3-1 July 2016
Specifications
Display: 4-digit LED display with 2 cm (0.8 in.) character height.
Display Range: 000.0-9999
Display Units: can be made to display in mR/hr, R/hr, µSv/h, mSv/h.
Linearity: Readings within 10% of true value with detector connected.
Operating Range: typically 0.1 mR/hr to 1R/hr
Status (green light): indicates the instrument is functioning properly
Low Alarm: indicated by a yellow light and slow beep (1 per second)
audible tone (can be set at any point from 0.0-9999)
High Alarm: indicated by a red light and a fast beeping, (4 per second)
audible tone (can be set at any point from 0.0-9999)
Note:
Audible indicators can be configured as a single beep if
desired. Audio intensity is controlled by rotating the baffle
on the audio device.
DET Fail: indicated by a red light and an audible tone greater than 68
dB at 60.1 cm (2 ft) for conditions of instrument failure or no count
from detector
Low Bat: indicated by a yellow light; less than 2 hours of battery life
remaining
Calibration Controls: accessible from the front of instrument
(protective cover provided)
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Instrument
Specifications

Model375-9 TechnicalManual Section3
Ludlum Measurements, Inc. Page 3-2 July 2016
Dead Time: adjustable to compensate for dead time of the detector
and electronics (can be read on the display)
Over-range: a display reading of ˝----˝and activated low and high
alarms indicate that the radiation field being measured has exceeded
the counting range of the instrument (or when dead time correction
accounts for more than 75% of the displayed reading)
Data Output: a 9-pin connector providing 5-decade log output, RS-232
output, signal ground connection, FAIL and HIGH ALARM signals
(current sink), and direct connection to battery and ground
RS-232 Output: a 2-second dump for computer data logging
Remote (optional): Ludlum Model 271 (part # 48-2475) or Model 272
(part # 48-2656) remote units
Power: 95-135 Vac (178-240 Vac available), 50-60 Hz single phase
(less than 100 mA), 6-volt sealed lead acid rechargeable backup battery
(built-in)
Battery Life: typically 48 hours in non-alarm condition; 12 hours in
alarm condition
Battery Charger: Battery is continuously trickle charged when the
instrument is connected to line power and turned on.
Warning!:
Only a certified technician or calibration personnel should
replace battery.
Construction: aluminum housing with ivory powder-coat finish
Size: 18.7 x 24.6 x 6.4 cm (7.4 x 9.7 x 2.5 in.) (H x W x D), excluding
detector
Weight: 2.9 kg (6.5 lb), excluding detector
Detector: external, typically a Model 45-9 or 45-9-1 ion chamber as
detailed below (others are available)
Detector Housing:aluminum with beige powder-coat finish, 7.6 x 25.7
cm (3 x 10.1 in.) (Diax L)
Ion Chamber: 17 cm3volume; stainless steel wall chamber filled with
Xenon at 7600 torrpressure
Detector
Specifications

Model375-9 TechnicalManual Section3
Ludlum Measurements, Inc. Page 3-3 July 2016
Energy Compensation: lead shield, 0.130 cm (0.051 in.) thick
Low Energy Cut-off: 60 keV
Range: typical configurations of 0.1 mR/hr through 1 R/hr, 1 mR/hr
through 10 R/hr, or 10 mR/hr through 100 R/hr. Selection of ranges
must be decided at time of purchase. Contact LMI for further details.
Detector Voltage: 150 V
Calibration Reference: 137Cs
Signal Output: transistor collector with internal pull-up resistor of 100
kΩconnected to a 5-volt supply line. This will supply a negative pulse
train proportional to the radiation field.
Power Supply: 5 V at up to 100 mA
Bias Output: With no radiation signal from the detector, the output
pulse rate is set at 400 counts per minute (cpm). This signal must be
subtracted from the radiation signal for good linearity.
Control: a multi-turn subsurface potentiometer for setting the bias
output. Start with the control fully clockwise, then slowly turn
counterclockwise until a count rate of 400 cpm is obtained.
Connectors: 5-pin circular; weatherproof
Warm-up Time: approximately 5 minutes

Model375-9 TechnicalManual Section4
Ludlum Measurements, Inc. Page 4-1 July 2016
Operator Controls and Setup
Calibration Controls
Remove the calibration cover to expose the calibration controls. The
calibration controls include the up/down buttons, three calibration
potentiometers, and the option dipswitch (detailed in the following
subsection). The three potentiometers are detailed below/
Warning!
Do not touch the circuit board in the calibration window
due to potential for electric shock.
RCDR: Used to adjust the logarithmic analog voltage output. Adjusted in
calibration mode to the full-scale voltage reading or adjusted to a known
point at some given reading.
THRESHOLD: Internal discriminator used to set the pulse threshold for
counting pulses from the detector. Pad allows direct measurement of
threshold voltage.
BAT CHARGE: Used to set the backup battery trickle charging voltage. It
is set to 6.9 Vdc while the battery is disconnected.
Dipswitch (under calibration cover)
When the calibration cover is removed, a four-pole dipswitch is accessible
that can activate or deactivate options. These four options are CAL MODE
(MEMWRITE), LATCH, ALARM, RANGE and SINGLE BEEP.
Dipswitch 1: Switching the top CAL MODE switch to the right places the
instrument into calibration mode. Parameters can only be changed while
the instrument is in calibration mode. Calibration mode also changes the
RCDR output to full-scale so that the full-scale voltage may be set by the
RCDR potentiometer. Moving the CAL MODE switch back to the left
locks the parameters and disables any further changes.
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Model375-9 TechnicalManual Section4
Ludlum Measurements, Inc. Page 4-2 July 2016
Dipswitch 2: The second switch, LATCH ALARM, changes the high
alarm to a latching alarm. This switch does not affect the low alarm,
which is always non-latching. When switched to the left, the high alarm
is non-latching; the alarm automatically turns off when the radiation
level drops below the alarm point. When switched to the right, the
highalarm light and audio signals are latched until either the LOW ALARM
or HIGH ALARM button is pressed.
Dipswitch 3: The third switch, RANGE, selects the range of the
instrument. To select the 0.1 <units> - 999.9 <units> range, switch the
RANGE switch to the left. To select the 1 <units> - 9999 <units> range,
switch the RANGE switch to the right.
Dipswitch 4: Switching the fourth switch to the right places the
instrument into SINGLE-BEEP mode. This option limits the audio
output to a single half-second beep on LOW ALARM and HIGH ALARM.
DET FAIL audio output (steady tone) is not limited.
RS-232 Output
With the CAL MODE dipswitch in the left position the Model 375-9 dumps
RS-232 data onto pin 4 of the 9-pin connector every two seconds.
An example program which shows how an IBM compatible PC can be used
to collect the data is given on following page.

Model375-9 TechnicalManual Section4
Ludlum Measurements, Inc. Page 4-3 July 2016
BYTE1 0 x
BYTE2 x x
BYTE3 x OR x
BYTE4 x x
BYTE5 . .
BYTE6 x 0
BYTE7 Audio Status =1=on
BYTE8 High Alarm Status=1=on
BYTE9 Low Alarm Status =1=on
BYTE10 Over Range Status=1=on
BYTE11 Monitor Status =1=on
BYTE12 Error Code
BYTE13 Carriage Return (ODH)
BYTE14 Line Feed (0AH)
The RS-232 data includes the
current radiation readings and the
current condition of the status
lights. The data is presented in the
following format:
'Demonstration Program
'Model 375-9 RS-232 communication program written for QuickBasic
'This program causes the computer screen to display the data being dumped from the Model 375-9.
'Needs the following cable:
' Model 375-9 PC (9-pin) PC (25-pin)
' pin4TXD pin2 pin3
' pin2GND pin5 pin7
'Cable connector has male pins on Model 375-9 side
'Cable connector has female pins on PC side
'openupcommunicationswithserialport#1
'at 2400 bps (baud), no parity, 8 data bits, 1 stop bit
'no handshaking, buffer size of 8k
OPEN "COM1:2400,n,8,1,bin,CS0,DS0,CD0, RB0" FOR INPUT AS #1
'openupfilename•foroutput
CLS 'clearthescreen
LOCATE 1
PRINT 'PressEsckeytostopreadingdata."
COM(1)ON 'enablecomltrapping
ON COM(1) GOSUB Getcomport 'if something comes in coml, then get it
WHILE(1) 'loopuntilEsckeyishit
comment• = INKEY•
IF comment• = CHR• (27) THEN GOTO endloop
WEND
endloop:
COM (1) OFF
CLOSE#1 'CLOSECOMport.
END
Getcomport:
WHILE LOC(1) <> 0
ComPortInput• = INPUT•(1 ,#1) 'bring in data from serial port
PRINT ComPortInput•; 'print data to screen
WEND
RETURN
1.

Model375-9 TechnicalManual Section4
Ludlum Measurements, Inc. Page 4-4 July 2016
9-Pin Data Connector
The 9-pin connector provides output signals from the instrument and
input voltage to the instrument. The pin assignments are:
pin1- +BATTERY
pin2- GND IN
pin3- FAIL_L
pin4- RS232 DUMP
pin5- RCDR
pin6- NA
pin7- HIGH ALARM_L
pin8- EXT RESET_L
pin9- +5VDC OUT
The FAIL and HIGH ALARM digital signal outputs are open drain 2N7002
outputs, able to sink about 50 mA each.

Model375-9 TechnicalManual Section5
Ludlum Measurements, Inc. Page 5-1 July 2016
Common Options and
Modifications
Time and Date Stamp Option
Description:
When an alarm or failure occurs the Model 375-9 will print the current
reading, date, time and either ALARM or FAIL to the RS-232 port. The Model
375-9 will print once every 30 seconds as long as the alarm or fail condition
is present.
Setup:
You will need the following: A Model 375-9 instrument, a 1220 40-
column printer, and a cable (8303-674).
The printer should be configured at 2400 BPS (baud), no parity, 8 data
bits, 1 stop bit, and no handshaking. See printer manual for proper
setup instructions.
Setting the date and time:
Check the month and day (MMDD) by pressing the LOW ALARM and
HIGH ALARM buttons simultaneously. The month and day will be
displayed as long as those buttons are pressed. The month and day can
be set from 0101 to 1231.
Check the year (YYYY) by pressing the LOW ALARM and CAL CONST
buttons simultaneously. The year will be displayed as long as those
buttons are pressed. The year can be adjusted from 0000 to 9999.
Check the hours and minutes (HHMM) by pressing the LOW ALARM
and DEAD TIME buttons simultaneously. The hours and minutes will
be displayed as long as those buttons are pressed. The hours and
minutes can be adjusted from 0000 to 2359.
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