Section 6
ZGARD S & DS NO2 (EC) RS485 Output Sensor
Calibration
Calibration Procedure, Electrochemical (EC) RS485 Output Nitrogen Dioxide Sensor:
Perform calibration checks
regularly as part of a routine inspection and maintenance procedure. Use calibration gases of known and certified
concentrations. Check the expiry date on the gas cylinders. The ZGARD S & DS sensor is factory calibrated for 0-10ppm
Nitrogen Dioxide, which represents 0 to 100% full scale. The output voltage of 1 to 5Vdc between the test points TPCAL and
TPCOM represents 0 to 100 % full-scale.
U
C
C
A
A
U
U
T
T
I
I
O
O
N
N
The calibration procedure must be completed after the replacement of sensing cells.
Calibration Equipment
Flow controller 0.25 litres/minute and tubing
Purified air as zero gas
10ppm NO2 in air span gas
Magnetic Strips
*
(Are only used on the ZGARD S Sensors)
Electronic Multi-meter
Calibration Procedure
1.
Disconnect the sensor output from the associated monitoring device. Using a multi-meter, insert two test probes into the
test point terminals labelled TPCAL & TPCOM.
2.
*
Place the magnetic strips on the top and bottom of the sensor cover plate, ensure the vent holes are fully covered.
U
W
W
A
A
R
R
N
N
I
I
N
N
G
G
Remove the magnetic strips after the calibration has been completed. Otherwise it could fail to perform as designed and
persons who rely on this product for their safety could sustain severe personal injury or death.
ZERO Calibration
3.
Attach a 0.25 l/m., flow controller onto a ZERO gas cylinder. On the ZGARDS S Sensor, insert a calibration adapter into
thread port provided on the protective cover located on the front plate. The ZGARD DS Sensor is provided with standard
calibration adapters.
4.
Connect ¼” Tygon tubing to the outlet of the flow controller, and then slip the open end on the calibration adapter.
5.
Turn ON the flow controller valve and allow the ZERO grade air to quench the sensor for at least 2 minutes.
6.
Adjust the ZERO potentiometer until the output voltage is equal to 1Vdc.
7.
Turn OFF the valve and remove the flow controller from the Zero gas cylinder.
SPAN Calibration
8.
Attach
the flow controller onto a SPAN gas cylinder. The SPAN gas should be at least 50% of the sensor’s operating
range.
9.
Turn ON the flow controller valve and allow the SPAN gas to quench the sensor for at least 2 minutes.
10.
Adjust the SPAN potentiometer until the output voltage is equal to the calculated value representing the gas
concentration.
SEE:
The example equation below.
11.
Turn OFF the valve and remove the flow controller from the SPAN gas cylinder.
12.
Remove the test hose from the calibration adapter.
13.
Remove the multi-meter test probes from terminals labelled TPCAL and TPCOM.
14.
Reconnect the sensor output to the associated monitoring device.
Example:
The SPAN gas concentration is
10ppm
Nitrogen Dioxide in air.
1-5Vdc is 0-100% F.S., the voltage that is generated is 4 + 1 = 5Vdc.
10ppm =
((Span Gas Value x 4) / Full Scale)) + 1
= ((10 x 4) / 10)) + 1 =
5.0Vdc
6.1
