Fluke Biomedical 945A User Manual
Page 76
5.
Adjust VR2 for a DVM reading of 10 ± 0.01 Volts. Return the full scale setpoint to the original
value. Return the full scale setpoint to the original value.
6.
Repeat steps 1 - 5 until adjustment interaction has been eliminated.
4 - 20 mA Analog Output Adjustment
The Model 946A contains two identical 4 - 20 mA current outputs; each independently adjustable for zero
and span. In the following steps, the adjustment potentiometers for output # 2 are given in parenthesis
following the output for #1 potentiometer. The adjustment must be performed with the device to be driven
with the output connected or with a standard 250 ohm, 1% termination resistor. The 4 - 20 mA output will
be measured as a 1 - 5 Volt signal developed across the input terminal of the driven device or across the
250 ohm resistor. It should be noted that the maximum loop resistance is 500 ohms for a signal output.
1.
Note the dose rate value on the display and set the analog low scale setpoint value (position 7 of
the 946A function switch) to the next even decade value above the display value.
2.
Connect the DVM to the desired 4 - 20 mA output. Output #1 is sourced from P6-1 (+) and P6-1 (-
). Output #2 is sourced from P6-3 (+) and P6-4 (-).
3.
Adjust VR7 (VR6) until the DVM reads 1 ± 0.005 Volts. Return the low scale setpoint to the original
value.
4.
Set the analog full scale value (position 4 of the 946A function switch) to the next even decade
value below the display value.
5.
Adjust VR4 (VR5) until the DVM reads 5 ± 0.005 Volts. Return the full scale setpoint to the original
value.
6.
Repeat steps 1 - 5 until adjustment interaction has been eliminated.
977-210 Detector Analog output Adjustments
The 977-210 Detector provides an independent 0 - 10 Volt analog output that may be used to drive a
local meter or display. This output is logarithmic and covers the entire 8 decade range of the device.
Adjustments for zero and span are located on the 977-210-10 interface circuit board. To perform the zero
and span adjustments, the DIP switch SW3-3 must be ON to place the detector in the maintenance mode
of operation.
1.
Place SW3-4 in the OFF position and connect the DVM to 977-210-10 connector J3-10 (+) and J3-
8 (-). Refer to drawing 977-210-10 for connector locations.
2.
Adjust potentiometer R53 for a DVM indication of 0 ± 0.01 Volts.
3.
Place SW3-4 in the ON position and adjust R19 for a DVM indication of 10 ±0.01 Volts.
4.
Repeat steps 1 through 3 until interaction of zero and span adjustments is minimized.
5.
Return SW3-3 to the OFF position to return the detector to normal operation.
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