Model DM-100
DM-100 Instruction Manual
Rev. 3.5
Page 16 of 41
3.3.1.1
Display Not Installed
1.
If a DM-100 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.
For toxic sensors, if the ambient air is known to contain no target gas content, then it can be used for
zero calibration. If a zero gas cal cylinder is going to be used, attach the calibration adapter and set
flow rate of 200-500cc/min (500cc/min is the recommended flow rate) and let the sensor purge for 1 to
2 minutes before zeroing the sensor. For O
2
deficiency sensors, apply N
2
at a set flow rate of
500cc/min for 3 to 5 minutes before zeroing the sensor.
NOTE:
For O2 deficiency sensors
N2 (99.99%)
MUST
be applied at a flow rate of 500cc/min for
a time period of 3 to 5 minutes to successfully zero calibrate the sensor.
3.
From Normal Operation, hold the programming magnet over
PGM1
for 3 seconds. The reading will
dip momentarily to 2mA (20mV on the meter). The reading will then return to 4ma. (The ideal reading
for zero is 4.03mA or 40.3mV.)
4.
Observe the reading for a minute or so to ensure that the reading does not drift.
5.
If zero gas was used, remove the gas from the sensor.
3.3.1.2
With Display
1.
For toxic sensors, if the ambient air is known to contain no target gas content, then it can be used for
zero calibration. If a zero gas cal cylinder is going to be used, attach the calibration adapter and set
flow rate of 200-500cc/min (500cc/min is the recommended flow rate) and let the sensor purge for 1 to
2 minutes before zeroing the sensor. For O
2
deficiency sensors, apply N
2
at a set flow rate of
500cc/min for 3 to 5 minutes before zeroing the sensor.
NOTE:
For O2 deficiency sensors
N2 (99.99%)
MUST
be applied at a flow rate of 500cc/min for
a time period of 3 to 5 minutes to successfully zero calibrate the sensor.
2.
From Normal Operation, hold the programming magnet over
PGM1
for 3 seconds. The display will
scroll
1-ZERO…2-SPAN
for 10 seconds.
NOTE
If no action is taken unit returns to normal operation after time expires, 10 seconds.
3.
Hold PGM1 to start Auto Zero routine, ZERO IN PROGRESS… will scroll across the display. Output
current from the sensor will drop to 3.5mA.
4.
Observe the reading for a minute or so to ensure that the reading does not drift.
5.
If zero gas was used, remove the gas from the sensor.
