Model DM-100
DM-100 Instruction Manual
Rev. 3.5
Page 12 of 41
1.
If the Loop Powered Display option is installed, the display should read
0.0
upon power up. If a Loop
Powered Display is not installed on the sensor, set a DVM to measure millivolts, and connect it across
TP1 and TP2 on the terminal board.
The DVM will read the voltage drop across a 10Ω resistor. The
resistor develops a 10mV voltage drop per 1mA of current. Thus a reading of 40mV on a DVM equals
4mA of current.
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).
