Fluke Biomedical 945A - Manual (Page 69)

Section 6 - Calibration
Calibration
The 977 Ion Chamber Detector is factory calibrated on a 137Cs/60Co range. A ± 15%, 10 point NIST
traceable factory calibration is performed to obtain a calibration factor for the detector. The calibration
factor is stated on the factory calibration data sheet, and is adsjusted via set-point 5 on the 946A UDR. A
field test source, P/N 848-5, is available as an option to verify detector operation. The
detector/preamplifier pair should be returned to Fluke Biomedical RMS for recalibration whenever
performance degredation is observed.
Electronic Adjustments
Table 6-1 lists the electronic adjustments for the 946A UDR and 977-210 preamplifier. The procedures
for making these adjustments are contained in the factory Calibration Procedure listed below. Note that
test firmware is required to perform the electrical adjustments. Refer to Section 7 for a description of user
permitted adjustments.
Table 6-1. Electronic Adjustments
Adjustment (UDR) Purpose Tolerance
VR1 Zero Adjust / 0 - 10 Volt Analog Output 0.000 Vdc ±5 mV
VR2 Gain Adjust / 0 - 10 Volt Analog Output ±.5% of full scale
VR4 20 mA Adjust / 4 - 20 mA Volt Analog Output #1 ±.5% of full scale
VR5 20 mA Adjust / 4 - 20 mA Volt Analog Output #2 ±.5% of full scale
VR6 4 mA Adjust / 4 - 20 mA Volt Analog Output #2 ±.5% of full scale
VR7 4 mA Adjust / 4 - 20 mA Volt Analog Output #1 ±.5% of full scale
VR13 Write Cycle Clock Adjust ±5 ns
Adjustment (977) Purpose
R11 Programmable Gain Amplifier Offset Adjustment ± 2 mV
R12 Auto Zero Set-Up Adjustment ± 10 mV
HV Supply R118 High Voltage Adjust ± 20 V
R53 Analog Output Adjustment ± 10 mV
Note
Refer to the drawings in Appendix B to locate adjustment and/or test points, if required.
WARNING
Sections of this circuit board contain voltages in excess of 500
volts. Use extreme care when making any adjustments.
Use extreme care when making high voltage measurements directly
at J6 or TP3.
The follow factory calibration and test procedures are included for reference.
Document Description
Cal-ION2 Factory Calibration Procedure for the 977 Detector
TP977-201/210 Test Procedure for 977 Series
LT946/977 Factory Loop Test for 945 System
TP946A-100-3 Factory Test Procedure for 946A-200
MB95-1004 Field Cable Termination for Replacement 977-210 Detector
TP-977 Cable Factory Test Procedure for 977-210-66 cables
6-1