Table of Contents
Advertisement
Diagnostic Procedures
Simple Zero Test
This test will ensure the unit is calibrated for a true
"zero" and duly represents an absence of target gas in
this condition.
Start: Set meter to mV DC, place meter leads on
Test(+) and Test(—) respectively (see Figure 28).
• Apply pure nitrogen (N2) into the calibration port at
a rate of .6 Liter/min. for at least 3 minutes. Check
the status of the yellow "system" LED. If this LED is
continuous ON, place the unit in non-filtered output
run mode by pressing both the "zero" (S1) and
"span" (S2) buttons simultaneously for 1 second or
until the "system" LED begins to blink slowly. See
example below.
• Wait until output signal has stabilized to within ± .02
mA of signal deviation/change.
• Output should read between 3.9 and 4.1 mA (39.0 to
41.0 mV).
If this is not the case, proceed to the next step.
• Follow the "zero" procedure above to re-zero the
unit
• Follow the "simple zero test" procedure to ensure
the unit is resting at the optimum 4 mA point.
Figure 28. Simple zero test, no "dead-band" mode, 0-26 mA
AirScan iR - Industrial
Exit: Press and hold both the "zero" (S1) and "span"
(S2) buttons simultaneously for 1 second or more until
"system" LED is continuous ON. Unit should be ready
for long-term operation.
4/20 mA Output Loop Integrity Check
22 mA High Signal Test
STEP 1
Start: Set meter to mV DC, place meter leads on
Test(+) and Test(—) respectively (see Figure 28).
• Press the "zero" (S1) button 5 times. The yellow
"calibrate" LED will blink fast and the yellow
"system" LED will turn off. The output should be 21
to 22.5 mA (210 to 225 mV).
If a problem exists on the output signal line, or the
output load is not within the specified range, the "mA
fault" LED will blink either before or upon activation of
this test. In some cases the 22 mA high signal output
will cause incorrect output load resistance values to
surface because of the demand on high resistances to
produce high currents.
Low power supply voltages can also be something to
investigate if this error surfaces only when the 22 mA
high test is initiated.
Figure 29. During 4-20 mA loop test (22 mA high)
19
Advertisement
Table of Contents
