Maintaining & Troubleshooting
Hardware Installation and Maintenance Manual B
–21
Table B-1 Potential instrument problems and solutions (Continued)
Symptom Response
Current loop is stuck at 4 mA or 20 mA Check display for fault message. If
alarm has been triggered, reset the
alarm.
On the current loop board, check the
voltage between the end of resistor R1
closest to the jumper and ground. If
the concentration reading is high, the
voltage should be near 1 VDC. If the
concentration reading is low, the volt-
age should be near 4.7 VDC. If not, the
problem is probably on the HC12 main
board. Return to factory for service,
refer to “Service Contact” on page
B-22.
Reading seems to always be high by a
fixed amount
See “Adjusting Analyzer Reading to
Match Specific Standard(s)” in the
Firmware Manual for this analyzer.
Capture diagnostic data and send the
file to SpectraSensors (see “To read
diagnostic data with HyperTermi-
nal” in the Firmware Manual for this
analyzer).
Perform a validation. Refer to Mode 7
or “Validating the Analyzer” in the
Firmware Manual.
Reading seems to always be high by a
fixed percentage
See “Adjusting Analyzer Reading to
Match Specific Standard(s)” in the
Firmware Manual of this analyzer.
Capture diagnostic data and send the
file to SpectraSensors (see “To read
diagnostic data with HyperTermi-
nal” in the Firmware Manual for this
analyzer).
Perform a validation. Refer to Mode 7
or “Validating the Analyzer” in the
Firmware Manual.
Reading goes to “0” If 4-20 mA Alarm Action is set to 0,
look on display for a fault message (see
“To change parameters in Mode 2
or Mode 3” in the Firmware Manual for
this analyzer).
Actual gas concentration may be equal
to zero. Perform validation using Mode
7 or “Validating the Analyzer” in the
Firmware Manual.
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