Ludlum Measurements 375 User manual

LUDLUM MODELS 375 (INCLUDING SERIES ONE),
375/1, 375/2 AND 375/4
DIGITAL WALL-MOUNT AREA MONITORS
May 2017
Serial Number 278020 and Succeeding
Serial Numbers

LUDLUM MODELS 375 (INCLUDING SERIES ONE),
375/1, 375/2 AND 375/4
DIGITAL WALL-MOUNT AREA MONITORS
May 2017
Serial Number 278020 and Succeeding
Serial Numbers

Ludlum Measurements, Inc. May 2017

Ludlum Measurements, Inc. May 2017
STATEMENT OF WARRANTY
Ludlum Measurements, Inc. warrants the products covered in this manual to be free of
defects due to workmanship, material, and design for a period of twelve months from
the date of delivery. The calibration of a product is warranted to be within its
specified accuracy limits at the time of shipment. In the event of instrument failure,
notify Ludlum Measurements to determine if repair, recalibration, or replacement is
required.
This warranty excludes the replacement of photomultiplier tubes, G-M and
proportional tubes, and scintillation crystals which are broken due to excessive
physical abuse or used for purposes other than intended.
There are no warranties, express or implied, including without limitation 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 the purchase, use, or
inability touse product.
RETURN OF GOODS TO MANUFACTURER
If equipment needs to be returned to Ludlum Measurements, Inc. for repair or calibration, please send to the address below. All shipments should include
documentation containing return shipping address, customer name, telephone number, description of service requested, and all other necessary
information. Your cooperation will expedite the return of your equipment.
LUDLUM MEASUREMENTS, INC.
ATTN: REPAIR DEPARTMENT
501 OAK STREET
SWEETWATER, TX 79556
800-622-0828 325-235-5494
FAX [phone]

Ludlum Measurements, Inc. May 2017
Table of Contents
Introduction 1
Getting Started 2
External Detector (Option) 2-1
Power Up 2-1
Radiation Units 2-2
Checking Parameters 2-2
*Model 375 Series One 2-3
Setting Alarm Points 2-3
Operational Check 2-4
Return for Repair and Calibration 2-5
Specifications 3
Operator Controls and Setup 4
Calibration Controls 4-1
Dipswitch (under calibration cover) 4-2
RS-232 Output 4-3
9-Pin Remote Data Connector 4-3
9-Pin Relays Connector 4-4
Typical Internal Detector Setups 4-4
Common Options and Modifications 5
Relay Options 5-1
Ethernet Interface Option 5-5
Time and Date Stamp Option 5-5
Printer DIP Switch Settings 5-6
Sigma Alarm Modification Option 5-7
4 to 20 mA Isolated Output Driver Option 5-8
Safety Considerations 6
Environmental Conditions for Normal Use 6-1
Cleaning Instructions and Precautions 6-1
Warning Markings and Symbols 6-2
Electrical Safety Precautions 6-3
Replacement of Main Fuse 6-4

Models375(Including Series One),375/1, 375/2 &375/4
Ludlum Measurements, Inc. May 2017
Detector Connector 6-4
Battery Replacement 6-4
Calibration 7
High Voltage 7-1
Calibration Parameters 7-1
Analog Output 7-2
Discriminator 7-2
Battery Charge 7-2
Recycling 8
Parts List 9
Model 375 Digital Wall-Mount Area Monitor without Detector 9-1
Model 375/1 Digital Wall-Mount Area Monitor 9-1
Model 375/2 Digital Wall-Mount Area Monitor 9-1
Model 375/4 Digital Wall-Mount Area Monitor 9-1
Model 375 Series One without Detector 9-1
Model 375/2 Series One 9-1
Model 375/4 Series One 9-1
Main Board, Drawing 558 x 1 9-1
Wiring Diagram, Drawing 558 x 136 9-6
Internal Detectors 9-6
Drawings and Diagrams 10

Models375 (Including SeriesOne),375/1, 375/2&375/4 Section1
Ludlum Measurements, Inc. Page 1-1 May 2017
Introduction
he Model 375 Digital Wall-Mount Area Monitor is designed for
visibility and ease of use. Featuring a wall-mount chassis, the Model
375 has a four-digit LED display that is readable from 9.1 m (30 ft)
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.
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. Depending on
the needs of the customer, the Model 375 comes equipped with an internal
detector or a connector for use with an external detector. The Model 375/1
comes equipped with an internal CsI scintillator detector. The Model 375/2
and 375/4 come equipped with internal, energy-compensated GM detectors.
The Ludlum Model 375 Series One is a Model 375 with modified firmware.
Changes include certain display values in decimal points and units. Details can
be found in sections “Getting Started” and “Specifications.”
Sectio
n
1
T

Models375 (Including SeriesOne),375/1, 375/2&375/4 Section2
Ludlum Measurements, Inc. Page 2-1 May 2017
Getting Started
he Model 375 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 will be discussed in this section. Other sections of the
manual provide more detailed information.
External Detector (Option)
Warning!
Potential electrical shock hazard - Do not touch the center
pin of the detector connector unless the unit has turned off
and power has been removed for at least one minute.
The Model 375 comes equipped with either an internal detector or a
connector for use with an external detector. If your Model 375 is equipped
with a connector on the bottom side of the chassis, an external detector is
required. If you have an external detector, use the cable provided to connect
it to the Model 375.
Note:
Splicing or re-terminating cables must be done carefully.
Improper termination will result in the “shorting out” of the
detector voltage, a DET FAIL, and/or blown-fuse condition.
Power Up
Plug the wall-mount 9 Vdc power supply into a suitable wall (Mains) outlet.
Sectio
n
2
T

Models375 (Including SeriesOne),375/1, 375/2&375/4 Section2
Ludlum Measurements, Inc. Page 2-2 May 2017
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 below and on pages 2-3 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 (396Nyy) is then displayed as "396" and "xxyy"
(where xx and 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.
Radiation Units
The Model 375 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
highalarm 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>*.