Specifications

M GD-100 M anual
6109-9000 Rev 3 43
6.9. Gas Calibration (Two-Alarm Units)
NOT E: This calibration procedure is for a two-alarm unit
.
For one-alarm units, refer to the previous section.
NOT E: The delay on a two-alarm system is approximately
25 seconds and cannot be deacti vated.
All adjustments are performed on the MGD-100 sensor P CB. The
Sensor Standby Voltage and two Alarm Threshol d Voltages must be
adjusted.
Step Adjusting the Sensor Standby Voltage (SSV)
1
Connect the voltmeter between TP 5 (0V ) & TP4 (+Ve) and
adjust pot RV1 for 0.3V (on IR units SSV is fixed).
Step Adjusting the Low Alarm Threshold Voltage (ATV)
2
Monitor the voltage between TP 5 (0V ) & TP4 (+Ve)/0V and
VS on IR units.
3
Apply the low concentration calibration gas to the sensor and
wait until the sensor out put signal stabilizes. Record this
voltage.
4
Adjust P8 to the new value. Rec ord and us e the new value
for subsequent electrical set-ups.
Step Adjusting the High Alarm Threshold Voltage (ATV)
5
Monitor voltage between TP 5 (0V) & TP4 (+Ve)/0V and VS
on IR units.
6
Apply the high concentration calibration gas to the sensor
and wait until the sensor out put signal stabilizes. Record this
voltage.
7
Adjust P7 to the new value. Record and use the new value
for subsequent electrical set-ups.
CAUTION: The high alarm threshold voltage must be set
higher than the low alarm t hres hold or the unit will not
function correctly.