The Victoreen® Model 943-227-15 Digital Preamplifier, is designed to operate with the Model 943-27,
Current Mode Beta Scintillation detector and the Model 942A-200C Series Digital Ratemeter (UDR) or the
Model 960 Series Digital Process Control system. When connected to the beta sensitive scintillation
detector, it comprises a monitoring system which operates in the range of 10
Pico amperes). The UDR provides display, control, and annunciator functions for the monitoring system.
The preamplifier contains a microprocessor controlled, auto-zeroing, integrating electrometer, a
programmable gain amplifier, an analog-to-digital converter and an asynchronous serial communications
interface. Communications with the UDR is accomplished via the optically isolated Victoreen Serial
Communication Loop driver/receiver circuitry.
Interconnection of the detector and preamplifier is accomplished utilizing two, six (6) foot coaxial cables.
One cable supplies the high voltage for the detector (negative polarity). The other cable is used for the
detector output signal. Interconnection between the preamplifier and the UDR or 960 system is
accomplished via a six-conductor cable and a high voltage coaxial cable.
The detector operates at a potential of approximately (-) 500 VDC, and produces a nominal DC output
current of 1 x 10
this corresponds to a range of 1 x 10
The preamplifier is a self-contained electronics unit that processes the DC input signal from the detector,
digitizes the signal, and transmits the digitized value to the readout via a modified RS232C compatible
serial data communication port. It contains two printed circuit boards (mounted on the rear of the
enclosure cover, a terminal block for terminating the field cable from its associated controller and two
connectors for terminating the detector Signal and HV coaxial cables. The larger of the two printed circuit
boards is the 977-210-10M Serial Interface board. This board controls the communications with the
controller. The smaller board is the 977-200-15M Electrometer. It contains the microprocessor and
associated circuitry for converting the detector output current into a digital value.
For additional information on the detector or readout device, refer to the instruction manual for the Model
943-27-31 detector, the Model 942A-200C UDR, or the applicable Model 960 System manual.
-12
amperes to 1 x 10
-4
amperes. Depending on sampling geometry and detector set up,
-3
to 1 x 10
+5
uCi/cc.
-3
to 105 uCi/cc (or 1E0 to 1E8
1.2 Application
The Model 943-227-15 Digital Preamplifier is used with the Victoreen 942A-200C or Model 960
microprocessor based radiation monitors. The Model 942A-200C or 960 system provides the +15 VDC
preamplifier electronics power, (-) 500 VDC detector power and the RS232C serial communications
support. The digital preamplifier is available in two serial port configurations. For applications less than
50 feet, the Model 943-227-15, configured for RS232C communications, is used. For applications
requiring signal transmission distances of up to 1 mile, the Model 943-227-15VL, configured for Victoreen
Loop communications is used. Table 1-1 is a list of available configurations and compatible 9XX series
equipment. Please contact Fluke Biomedical Radiation Management Services for additional information.
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1
943-227-15 Digital Preamplifier
Operator Manual
Table 1-1. 943-227-15 Variations and Compatible Equipment
Preamplifier
Variations
943-227-15 Digital
Preamplifier
943-227-15VL Digital
Preamplifier
943-227-15VL-M1
Digital Preamplifier
Application Detector Readout
Transmission
Distances
Less than 50 feet
Transmission
Distances up to 1
mile
Transmission
Distances up to 1
mile; 2.0 inch conduit
field cable interface
943-27-31 Beta
Detector,
Current Mode
Operation
943-27-31 Beta
Detector,
Current Mode
Operation
943-27-31 Beta
Detector,
Current Mode
Operation
942A-200C Digital Ratemeter
or Model 960 Digital Process
Control System
942A-200C Digital Ratemeter
or Model 960 Digital Process
Control System
942A-200C Digital Ratemeter
or Model 960 Digital Process
Control System
1.3 Specifications
General specifications for the Model 943-227-15 Digital Preamplifier are listed below. The 943-227-15
series products are designed for nuclear applications, and any repairs to it by personnel not qualified to
ANSI 45.2.6 1978, Skill Level II may void the nuclear rating.
If a problem develops, the preamplifier may either be returned to the factory for service, or repaired by a
qualified technician.
1-2
Table 1-2. General Specifications for the 943-227-15 Digital Preamplifier
Feature: Specification:
Preamplifier Power
Preamplifier Input
Preamplifier Output
Electronic Accuracy
Response Time
Dimensions
(H x W x D)
Weight
Housing
Operating Temperature
Relative Humidity
Compatible Detectors
Detector Interface
Cable Requirements
Modification
Information
+ 15 v @ 20 mA
DC current, 1E-12 to 1E-3 amperes from 943-27 Current Mode Beta
Scintillation detector
943-227-15, RS232C;
943-227-15VL, Modified RS232C serial data for transmission distances up
to 5,280 feet.
8.0 in. x10.0 in. x 4.0 in.
(20.3 cm x 25.4 cm x 10.2 cm)
943-227-15-M1 or 943-227-15VL-M1:
8.0 in. x10.0 in. x 6.0 in.
(20.3 cm x 25.4 cm x 15.2 cm)
Approximately 8 lbs. (3.6 kg)
Gasketed, NEMA 4, Steel enclosure with hinged cover
32 °F to 122 °F
0 °C to + 50 °C
0 to 99 % non-condensing
Victoreen 943-27 Current Mode Beta scintillation detector only
Detector cables enter thru “Seal Grip” fittings; Mating SHV receptacle
provided for HV; Mating BNC receptacle provided for Signal
Victoreen Loop Communications: 6 conductors, 18 AWG (2, TwPr, 2 Single
conductor) with overall shield. For max transmission distance, 16 AWG is
recommended;
RS232C communications: 8 Conductors, 18 AWG (4 TwPr) with overall
shield.
For the Model 943-227-15VL-M1, refer to Modification description provided
in Appendix E
General Information
Application
1
1-3
943-227-15 Digital Preamplifier
Operator Manual
Table 1-3. Preamplifier Serial Interface Board 977-210-10M Switch Settings
Switch Normal
Op.
SW1 Open Microprocessor Reset switch, momentary contact
SW2 N/A Not supplied
SW3-1 ON OFF Selects 300 baud • 1/ON Selects 4800 baud (normal setting)
SW3-2 OFF OFF • (No function is implemented in the 977-210-10M)
SW3-3 OFF OFF Selects Rate Mode (normal) • (Selects Maintenance Mode for
SW3-4 OFF OFF • (No function is implemented in the 977-210-10M)
Switch Function
factory PGA and Auto Zero set-up only)
NOTE
SW3 is a 4-position DIP switch on the 977-210-10M serial
interface board.
Table 1-4. Jumper Positions for Preamplifier Serial Interface Board 977-210-10M
Jumper Normal Setting Function Alternate Setting Function
JMP1 A to B
JMP2 N/A Deleted, Not Used N/A Deleted, Not Used
Table 1-5. Jumper Positions for Preamplifier Electrometer Board 977-200-15M
Jumper Normal Setting Function Cal. Position Function
JMP1 A to B Normal Operation B to C PGA Offset Adjust *
* Programmable Gain Amplifier requires a special test PROM and is a factory adjustment
Enables Victoreen Loop
(normal)
B to C Enables RS232C
1-4
Table 1-6. Field Electrical Connections, 943-227-15 and 943-227-15VL
General Information
Specifications
1
943-227-15
TB1- Description
1 XMIT
2 DTR
3 GND
4 REC
5
6
7 + 15 VDC J3-7 Not Used
8 Ground
9 - 15 VDC J3-4 Not Used Not Used
10 Not Used Not Used Not Used J3-11
HV Detector MHV
SIG Detector BNC
Table 1-7. 977-210-10M LEDs
LED # Indicates
LED1 +15 VDC is being supplied to the circuit board
LED2 Communications – Receive;
Table 1-8. 977-210-10M Test points
Test Point Function
TP2 RS232 Transmit
Not Used
Not Used
Detector
Connections
from the UDR when ON
ON (bright): both + 15 and -15 volt loops
present
ON (dim): Only one loop supply present
OFF: no loop voltage from either supply
Connects To
977-210-10M
J4-1
J4-2
J4-3
J4-4
Not UsedNot Used
J3-8
From Field
coaxial cable
Factory
Terminated,
To 977-200-
15M, R41
943-27-15VL
Description
+ VL, 15
VDC
+ TX
- TX
- VL
+ RX
- RX
Ground
Detector
Connections
Detector
MHV
Detector
BNC
Connects To
977-210-10M
J3-1
J3-2
J3-3
J3-4
J3-5
J3-6
Not Used
J3-8
From Field
coaxial cable
Factory
Terminated,
To 977-200-
15M, R41
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943-227-15 Digital Preamplifier
Operator Manual
1.4 Auxiliary Equipment
Model Description
None
1.5 Recommended Spare Parts
Table 1-9. Recommended Spare Parts List for the Model 943-227-15 Digital Preamplifier
Part Number Description Used On
977-200-15M Electrometer Circuit Board -
977-210-10M Serial Interface Circuit Board -
92-7072 Fuse, F1, F2, 1Amp, Communication Fuse
450-1-0531 Dryer, Air (5 Grams)
977-210-10M
977-200-15
1.6 Receiving Inspection
Upon receipt of the unit:
1. Inspect the carton(s) and contents for damage. If damage is evident, file a claim with the carrier and
notify the Fluke Biomedical Radiation Management Services Customer Service Department.
Fluke Biomedical
Radiation Management Service
6045 Cochran Road
Cleveland, Ohio 44139
Phone: 440.248.9300
Fax: 440.542.3682
2. Remove the contents from the packing material.
3. Verify that all items listed on the packing list have been received and are in good condition.
NOTE
If any of the listed items are missing or damaged, notify the
Fluke Biomedical Radiation Management Service Customer
Service Department.
1-6
General Information
Spare Parts/Receiving Inspection
1
1.7 Storage
Storage of Fluke Biomedical instruments must comply with Level B storage requirements as outlined in
ANSI N45.2.2 (1972) Section 6.1.2(.2). The storage area shall comply with ANSI N45.2.2 (1972) Section
6.2 Storage Area, Paragraphs 6.2.1 through 6.2.5. Housekeeping shall conform to ANSI N45.2.3 (1972).
Level B components shall be stored within a fire resistant, tear resistant, weather tight enclosure, in a
well-ventilated building or equivalent.
Storage of Fluke Biomedical instruments must comply with the following:
1. Inspection and examination of items in storage must be in accordance with ANSI N45.2.2 (1972)
Section 6.4.1.
2. Requirements for proper storage must be documented and written procedures or instructions must
be established.
3. In the event of fire, post-fire evaluation must be in accordance with ANSI N45.2.2 (1972), Section
6.4.3.
4. Removal of items from storage must be in accordance with ANSI N45.2.2 (1972), Sections 6.5 and
6.6.
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(Blank Page)
Theory of Operation
Functional Description
2
Section 2
Theory of Operation
2.1 Functional Description
The Model 943-227-15 Digital Preamplifier is an eight-decade, linear reading radiation. The preamplifier
is sensitive to moisture and is mounted in a NEMA 4 sealed enclosure. The preamplifier box contains a
desiccant package to remove moisture from the interior of the preamplifier. The desiccant has a color
indicator to show when it should be replaced when the color changes to blue.
The detector electrometer converts the current from the detector to a voltage which is measured by the
analog to digital converter of the preamplifier. Under program control, this measurement is made every
50 milliseconds on the first five decades and every 100 milliseconds on the upper three decades.
The electrometer is auto-ranging and auto-zeroing. An internal coarse zero control (factory adjusted) is
provided. The microprocessor in the preamplifier performs data collection, integration and multiplication
by a stored calibration factor, range changing and communication with the Model 942A-200C Digital
Ratemeter or Model 960 Digital Process Radiation monitoring system.
2.2 Main Circuit Boards
The wide range ion chamber detector block diagram is shown in figure 2-1. Detector electronics are
contained within two circuit board assemblies located in the preamplifier enclosure: the 977-210-10 High
Voltage/Communications Interface circuit board assembly and the 977-200-15 Electrometer circuit board
assembly. Schematic diagrams are located in Appendix B.
The 977-200-15M Electrometer circuit board contains the microprocessor, the EPROM, the integrating
electrometer, the programmable gain amplifier, the analog to digital (A/D) converter, and the auto zero
DAC circuit.
The 977-210-10M Communications Interface circuit board contains the dc voltage regulator, the BDC/DC
converter, the asynchronous communication interface adapter (ACIA), the Victoreen communication loop
driver/receiver, the RS232 communications driver/receiver, and the communication loop fuses.
2.3 977-200-15M Electrometer
Refer to the electrometer schematic 977-200-18M located in Appendix B. Z7 is a Texas Instruments TMS
70C00 microprocessor, which is utilized to control detector operation. Z8 latches port C of the
microprocessor to form the lower order bits of memory address. Z10 is a 27C64 EPROM containing the
operational firmware for the detector. Z18 is an optional RAM socket which is not utilized for this model
detector. Z9 is a decoder for the upper order address bits. Z11 is a latch used to store control bits to
select the gain of the programmable gain amplifier formed by the combination of Z5, Z4, and RN2.
Available gains are 1 through 128 in binary increments 1, 2, 4, . . . 128. Z3 is an eight-bit analog to digital
converter used to digitize the output of the programmable gain amplifier. Analog switch Z17 pin 11
selects either the integrating electrometer or the high voltage sense line as the input to the programmable
gain amplifier is not active in this application. Refer to Table 2-1 for preamplifier register addresses and
Table 2-2 for electrometer control bit assignments.