35-3001A-01-XX1 Sample-Draw Detector Operator’s Manual • 27
2. Screw the regulator into a zero air calibration cylinder.
3. Open the housing door.
4. Set a voltmeter to measure in the millivolt (mV) range.
5. Plug the positive lead into the red (+) amplifier test point; plug the negative lead into the
black (-) amplifier test point labeled.
6. Use the following formula to determine the correct test points output for the calibrating
sample.
Output (mV) = (calibrating sample/fullscale) X 400 + 100
For example, with a calibrating sample of 50% LEL and a fullscale setting of 100% LEL,
the correct output is 300 mV.
300 (mV) = (50/100) X 400 +100
Setting the Zero Reading
1. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s
inlet line.
This step is not necessary if you verified a fresh air environment earlier in
this procedure.
2. Allow the sample-draw detector to draw sample for one minute.
3. Verify a voltmeter reading of 100 mV (± 2 mV).
4. If necessary, use a small flat-blade screwdriver to adjust the zero potentiometer until the
voltmeter reading is 100 mV (± 2 mV). If you used a zero air calibration cylinder to set the
zero reading, proceed to step 5. If you verified a fresh air environment, proceed to the next
section, Setting the Response Reading.
5. Disconnect the sample tubing from the inlet line.
6. Unscrew the regulator from the zero air calibration cylinder.
Setting the Response Reading
1. Screw the regulator into the calibration cylinder.
2. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s
inlet line.
3. Allow the sample-draw detector to draw sample for one minute.
4. When the reading on the voltmeter stabilizes, verify that the reading matches the response
reading (±2 mV) you determined earlier.
5. If necessary, use the span potentiometer on the amplifier to adjust the reading to match the
correct response reading.
6. Disconnect the sample tubing from the inlet line.
7. Unscrew the regulator from the calibration cylinder.
