Oldham SV 4B - Acknowledgement of Gas Alarms

16
If you wish to lock the alarm relays (inhibiting the relays) during these alarm threshold adjustments:
set the maintenance switch to the high position (item 2, Fig. 7).
(
Caution: When the adjustments have been made, do not forget to place the switch back in its
normal position.
Terminal posts (item 3, Fig. 7) are used to connect up a voltmeter for the reading of a signal (in
mV) corresponding to the content level of the injected gas.
Then, using a rule of three, it is possible to calculate and adjust another signal (in mV) for an alarm
threshold (potentiometer: item 1, Fig. 7) corresponding to a different gas content level.
For example: when you inject 1% methane, you read 1,000 mV (for instance).
If you set the alarm potentiometer to read 1,500 mV, the alarm is triggered at 1.5%
methane.
Signal =
mV
mV
mVx
1500
1000
%11000

Or
Threshold (%) =
1% 1500
1000
15%
x mV
mV
 .
4.4.2. Acknowledgement of gas alarms
A switch (item 4, Fig. 7) is used to acknowledge gas alarms in manual mode
4
or automatic mode
5
.
(
Remark: As long as there is a high enough concentration of gas to trigger an alarm, it is
impossible to clear that alarm manually (with the Ack. button).
4
Manual mode: When a gas alarm is triggered, it must be cleared manually even if the content level has fallen to zero
(or to below the threshold). This is done by pressing the Ack. key (item 5, Fig. 7).
5
Automatic mode: When a gas alarm is triggered, it is cleared automatically as soon as the content level falls below the
alarm threshold.
Up )
Maintenance
Normal
Up )
Automatic ack.
Manual ack.