Honeywell VA201T Calibration Handbook page 96

Calibration Handbook
Span Calibration
This procedure sets the "span" or concentration level that would depict a 20mA reading for full-scale target
gas on the 4/20mA output.
NOTE: This procedure should only be performed if the zero procedures are successfully completed.
1. If not already in place, set meter to mV DC and place meter leads on Test(+) and Test(—) respectively.
2. Press and hold "span" button (S2) for 1 second or more until the yellow "calibrate" LED blinks fast and
the yellow "system" LED is blinking slowly (see the following example). See Figure 11 for switch and
potentiometer location.
3. Ensure the output rests between 3.9 and 4.1mA (39.0 to 41.0mV).
4. If this is not the case, perform the "zero" procedure again.
5. Once the output is within the required range, apply full-scale target gas into the calibration port at a rate
of 1.0 L/min for 1 minute.
If the signal is 20mA (200mV) or greater, adjust the "span" potentiometer counter-clockwise until the
signal is near 20mA (200mV).
If the output signal is less than 20mA (200mV), adjust the "span" potentiometer clockwise until the signal
is near 20mA (200mV).
Because there is a slight delay in potentiometer movement, make small adjustments and wait for the
output to change because adjustment response is delayed between source pulses.
6. Wait until the output signal has stabilized to within ± .02 mA (0.2mV) of signal deviation/change.
7. Adjust the "span" potentiometer again until the output reads around 20 mA.
8. Press and hold "span" button (S2) for one second or more until the yellow "calibrate" LED turns off.
96 IR-F9 / AirScan IR