GasSens
Gas Detection System
Section 5 - A11-10 Br2 Sensor/Transmitter
O & M Manual
Revision E, 10/15
5 - 7
TRANSMITTER SPAN
To span the sensor/transmitter, select the calibration generator output range of 1 PPM and allow
the generator to warm up for approximately 30 minutes. Connect the output tube from the standards
generator to the sensor calibration adapter. If using span gas from another source , connect the span gas to
the calibration adapter using non-reactive tubing, preferably Teflon, and adjust span gas flow to
approximately 500 cc/min. The reading on the DVM attached to the transmitter test points will
immediately start to increase. Allow the gas to flow to the sensor for 10 minutes and observe the reading
on the DVM. The reading should be relatively stable ± 0.05 VDC. Use the span potentiometer to adjust
the DVM to read 0.50 volts.
If a chlorine standard of another value is being used, or if the transmitter range is not the standard
0-2 PPM, calculate the calibration voltage using the following formula.
V = 1.00 X (Span Gas Concentration ÷ Transmitter Range)
As an example, if your span gas is marked with a concentration of 3 PPM Cl2 and it is used to
calibrate a 0-5 PPM sensor/transmitter, the calculation would be:
V = 1.00 X (3 ÷ 5) = 0.66 VDC
Remove the calibration adapter from the sensor, and replace the Auto-Test generator if in use.
Place the lid back on the transmitter enclosure and tighten the screws to insure the enclosure remains water
tight. If the receiver is nearby and the alarm relays were inhibited prior to calibration, press the
A/R
switch
to return the system to normal operation.
SENSOR RESPONSE TEST
While zero and span adjustments are required only periodically, gas sensors should be checked
regularly for proper response. For systems not equipped with Auto-Test, manual sensor response testing
once a week is recommended. The response test can be done using powdered calcium hypochlorite (HTH)
available from any swimming pool supply.
The sensor response test will create a condition where alarm relays will be activated unless they
are inhibited as described in the receiver section. To observe the response at the transmitter, it is necessary
to connect a DVM to the test points indicated in Figure 5-2. If the receiver is nearby, you may simply
observe the digital display on the receiver.
Place a teaspoon of calcium hypochlorite into a plastic bottle and keep the bottle capped until
ready to test the sensor.
Open the bottle and place the mouth near the sensor. The DVM reading will rise
rapidly. Immediately remove the bottle as it is best to expose the sensor to the high concentrations as
briefly as possible. If the sensor does not respond when the bottle is held near the sensor, the sensor must
be replaced. Normally, this will occur between 18 and 24 months after installation but could be longer.
For systems not equipped with Auto-Test, sensor replacement after 24 months is recommended.
The sensor response test described above should also be used if the Auto-Test systems detects a
sensing failure and lights the Trouble lamp. If this occurs, place the mouth of the bottle near the opening
between the sensor and generator. If the sensor does not respond, sensor replacement is required. If the
sensor responds to the chlorine coming from the bottle, activate the generator manually to see if chlorine
gas is being generated. If the sensor does not respond, replace the generator.