Model 43-37, 43-37-1 Gas Proportional Detectors
December 2016
page 3
Model 43-37-1 –100 cc/min for 45
minutes
A faster flush time can be achieved by
increasing the flow rate. (In general, if the
flow rate is doubled, the flush time can be
cut in half.)
CAUTION:
The main supply should be reduced to less
than 50 cc/min before the output gas line is
reconnected.
After flush is complete, set flow to
30-50 cc/min.
Check output flowmeter. Determine
detector leakage to be less than 5
cc/min.
6. DETECTOR PERFORMANCE
ALPHA PLATEAU: Determine the
plateau region of the background and alpha
source counting curves for the applied
voltage range of 1100-1400 volts. Use 50-
volt increments and set the counting
instrument input sensitivity at 4 mV. The
operating voltage should be approximately
1250 volts. The background count should
be 10 cpm or less. The operating voltage
will increase with a higher input sensitivity.
Check each section of the detector face for
statistically uniform response, that is, ensure
that each section reading is within 10% of
the average of the readings. If the count is
not statistically uniform, check for light
leaks in the window and repeat flush
procedures.
BETA-GAMMA PLATEAU: Determine
the plateau region in the background and
beta-gamma source counting curves for the
applied voltage range of 1500 volts to 1900
volts or from 1500 volts to when either the
source or background count rate increases
dramatically. Use 50-volt increments and
leave the input sensitivity at 4 mV. The
operating voltage should be approximately
1700-1800 volts, with the background count
as stated in Section 2 Specifications. Setting
instrument input sensitivity greater than 4
mV will increase the operating voltage.
7. STATIC OPERATION.
Check detector for proper operation, for
appropriate source count, and gas
leakage.
Disconnect output and input male quick
connects.
Turn main supply to OFF.
Check source count before and after
static operation. A decrease in detector
efficiency should be less than 10% in 15
hours from when the detector is
disconnected from main gas supply.
NOTE: There is expected performance
degradation along the sides of the probe and
within an inch of the standoffs.
