Honeywell Manning AirScan iR Instruction And Installation Manual page 20

AirScan iR - Industrial
Figure 25. Board component layout
STEP 3
Span Calibration
This procedure sets the "span" or concentration
level that would depict a 20 mA reading for full-scale
target gas on the 4/20 mA output. The lower the target
gas concentration is for a span of 20 mA, the more
sensitive or responsive the unit would be to lower ppm
readings.
NOTE: This procedure should only be performed if
the zero and 4/20 mA procedures are successfully
completed.
Start: Set meter to mV DC, place meter leads on
Test(+) and Test(—) respectively (see Figure 9).
Apply pure nitrogen (N2) into the calibration port
at a rate of .6 Liter/min. for at least 3 minutes (OR
until output signal has stabilized to within ± .02 mA
of signal deviation/change). If N2 is currently flowing
from previous "zero" calibration, disregard the
additional flow time.
18
Press and hold the "span" button (S2) for 1 second or
more until the yellow "calibrate" LED blinks fast and
Figure 26.
the yellow "system" LED is blinking slowly. See the
following example.
Figure 27. Span calibration
Ensure the output rests between 3.9 and 4.1 mA (39.0
to 41.0 mV). If this is not the case, perform the "zero"
procedure again.
Once the output is within the required range with
nitrogen flowing, apply full-scale target gas into the
calibration port at a rate of .6 liters/min for 3 minutes
immediately following the nitrogen flow.
If the signal is 26 mA or greater, adjust the "span"
potentiometer counter-clockwise until the signal
is near 20 mA. 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.
Wait until the output signal has stabilized to within
±.02 mA of signal deviation/change. Adjust the "span"
potentiometer again until the output reads around 20
mA.
Exit: Press and hold the "span" button (S2) for one
second or more until the yellow "calibrate" LED turns
off. The yellow "system" LED will resume the previous
state, either "filtered" or "non-filtered" output mode.
This indicates the parameters are now programmed
into memory.