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Model 400E Ozone Analyzer
Instruction Manual
11.1.2. Fault Diagnosis With Test Functions
Besides being useful as predictive diagnostic tools, the Test Functions viewable
from the Front Panel can be used to isolate and identify many operational problems
when combined with a thorough understanding of the analyzers Theory of
Operation (see Section 10).
The acceptable ranges for these Test Functions are listed in the "Nominal Range"
column of the analyzer Final Test and Validation Data Sheet (p/n 04314) shipped
with the instrument. Values outside these acceptable ranges indicate a failure of
one or more of the analyzers subsystems. Functions whose values are still within
the acceptable range but have significantly changed from the measurement
recorded on the factory data sheet may also indicate a failure. A worksheet has
been provided in Appendix C to assist in recording the value of these Test
Functions.
The following table contains some of the more common causes for these values to
be out of range.
Test
Functions
(As Displayed)
TIME
RANGE
STABIL
O3 MEAS
&
O3 REF
(table continued)
P/N 04316 Rev: B
Table 11-2: Test Functions - Indicated Failures
Time of Day clock is too fast or slow.
§ To adjust see Section 6.3.5.
§ Battery in clock chip on CPU board may be dead.
Incorrectly configured Measurement Range(s) could cause response problems
with a Datalogger or Chart Recorder attached to one of the Analog Output.
If the Range selected is too small, the recording device will over range.
If the Range is too big, the device will show minimal or no apparent change in
readings.
Indicates noise level of instrument or stability of the O3 concentration of Sample
Gas.
If the value displayed is too high the UV Source has become brighter. Adjust the
variable gain potentiometer on the UV Preamp Board in the optical bench.
If the value displayed is too low:
§ < 100mV – Bad UV lamp or UV lamp power supply.
§ < 2000mV – Lamp output has dropped, adjust UV Preamp Board or replace
lamp.
If the value displayed is constantly changing:
§ Bad UV lamp.
§ Defective UV lamp power supply.
2
§ Failed I
C Bus.
If the O3 Ref value changes by more than 10mV between zero and span gas:
Defective/leaking switching valve.
§
TROUBLESHOOTING & REPAIR PROCEDURES
Indicated Failure(s)
247
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