Oldham Surveyor 4B, User Manual

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16 Surveyor 4B
User Manual
When the adjustments have been made, do not forget to place
the switch back in its normal position.
Terminal posts item 3, Figure 8) 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, Figure 8) 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
% 1 1000

Or
Threshold (%) =
1% 1500
1000
15%
x mV
mV

.
Acknowledgement of gas alarms
A switch (item 4, Figure 8) is used to acknowledge gas alarms in manual
mode
4
or automatic mode
5
4
manuel : 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, Figure 8).
5
Automatic mode: When a gas alarm is triggered, it is cleared automatically as soon as the
content level falls below the alarm threshold.
Automatic ack.
(
↑ Up)
Manuel ack.