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AirScan iR - Industrial
Error on 4/20 mA output or during 4/20 mA
test 20 mA high
Figure 34. Error on 4/20 mA output or during 4/20 mA test
To resolve this issue, Place a resistor having at least
100 to 250 ohms across the signal output (SIG) and
ground (GND). The "mA fault" LED will stop blinking
indicating the load or wiring has a problem.
Sensor Output at 0 mA
Verify +24 VDC at the sensor terminal block (see
Figure 10, Note 1 on previous page).
Check signal voltage between Test(+) and Test(—)
(see Figure 10, Note 2). Voltage should be in the range
of 40 to 200 mV corresponding to an actual current
flow of 4 to 20 mA. If this voltage is 0 mV, the signal
has no path to ground. Check monitoring equipment
connections and configuration. Input impedance must
be 500 ohms or less.
Sensor Output at 0.5 mA
Please see Section D on page 15 for possible fault
conditions related to .5 mA output.
22
Gas Concentration Indicated With No Re-
frigerant Present
The AirScanTMiR is designed to be quite specific to
CFC/HCFC/HFC's that are colorless, odorless gases
which can't be sensed by humans at low levels.
Always double-check with another instrument before
assuming refrigerants are not present.
Performing a zero and a span calibration using
certified calibration gas will confirm or correct the
sensor's reading.
IR Source Failure
If the IR source signal strength drops to the point
that the unit can no longer function satisfactorily,
the "fault" LED will remain continuous ON and the
4/20 mA output will be set to 0.5 mA. See example
below. This condition can also occur in environments
where there is a significant amount of particulate
contamination.
Usually is takes an appreciable amount of time for
the particles to pose signal degradation, however,
under long-term exposure the filter surface could be
dirty causing low thermal readings, hence marginal
operation for signal analysis.
Figure 35. IR source failure
NOTE: 4/20 mA will be set to 0.5 mA.
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