Detcon DM-100 - Manual (Page 16)

Model DM-100
DM-100 Instruction Manual Rev. 3.3 Page 12 of 40
2. A temporary upscale reading may occur as the sensor stabilizes. This upscale reading will decrease to
"0" ppm (40mV on the DVM) within 1 to 2 minutes of power-up, assuming there is no gas in the area
of the sensor.
NOTE The 4-20mA signal is held constant at 4mA for the first two minutes after power up.
3. Sensors cells that use a bias voltage require a longer time to stabilize. This can vary between 1 and 24
hours depending on the sensor type and range. Biased sensors include NH
3
, NO, HCl, and VOC gases
(ethylene oxide, ethylene, methanol, formaldehyde….etc).
Initial Operational Tests
After a warm up period of 1 hour (or when zero has stabilized), the sensor should be checked to verify
sensitivity to the target gas.
Material Requirements
 Detcon PN 613-120000-700 700 Series Splash Guard with integral Cal Port and Calibration Wind
Guard (P/N 943-000000-000) -OR-
 Detcon PN 943-000006-132 Threaded Calibration Adapter - OR -
 Detcon PN 943-01747-T05 Teflon Calibration Adapter for highly reactive gases
 Detcon Span Gas; 50% of range target gas in balance N2 or Air at fixed flow rate between
200-500cc/min (500cc/min is preferred)
 DVM (if a loop powered display is not installed)
NOTE
Calibration gas generators using perm tubes or electrochemical sources may be used in
place of span gas cylinders.
NOTE
The cover of the junction box will need to be removed if there is not a loop powered
display. The area may need to be de-classified.
1. If the sensor has a loop power display installed, the display should read "0". If a DVM is used to
measure the 4-20mA output, set the DVM to measure millivolts and connect the leads across TP1 and
TP2 on the terminal board. The DVM should read 40±2mV.
2. Attach the calibration adapter to the Splash Guard adapter or connect tubing to integral cal port. It is
recommended that the Wind Guard (PN 943-000000-000) in installed over the Splash Guard during
calibration. Apply the test gas at a controlled flow rate of 200-500cc/min (500cc/min is the
recommended flow). If the sensor has a loop power display attached the reading should increase to
50% of full range (if the range is 100, the display should read 50). Observe that the DVM increases to
a level near that of the applied calibration gas value. Typically this would be 50% of full range, a
reading of 120±2mV (12mA).
3. Remove test gas and observe that, if the sensor has a loop power display installed, the display
decreases to "0". If a DVM is used the DVM reading should decrease back to 40mV (4mA).
4. If a calibration adapter was used during these tests, remove them from the unit, and re-install the
Splash Guard. If the wind guard was used, remove the wind guard.
Initial operational tests are complete. DM-100 toxic gas sensors are factory calibrated prior to shipment, and
should not require significant adjustment on start up. However, it is recommended that a complete calibration
test and adjustment be performed 16 to 24 hours after power-up. Refer to zero and span calibration instructions
in Section 3.3, Calibration.