Rosemount 755, Инструкция по эксплуатации

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M
ODEL
755 O
XYGEN
A
NALYZER
7-2
748183-H
Rosemount Analytical December 1997
Admit downscale and upscale standard gases to the analyzer; observe readout on
meter, and on recorder if used:
Meter reads correctly with standard gases but not with sample gas , the sample
and the sample-handling system are suspect. Check these areas.
Meter reads correctly with standard gases but the alarm or output devices do
not
, these devices must be checked individually.
Meter reads offscale or erratic with standard gases, as well as with sample gas ,
the trouble is probably in the detector or the electronic circuitry.
•
Offscale - Indication. If meter drives offscale in either direction, turn off power;
tap detector compartment with fingers; wait 30 seconds; then again apply
power. If the suspension within the detector assembly is hung up, this
procedure may correct the condition. If not, proceed with tests of detector and
electronics.
•
Erratic - If downscale and upscale standard gases give noisy or drifting
readings, the trouble is probably in the detector or the temperature-control
circuits. Proceed with test of detector and electronics. In general, before
concluding that the detector is defective and must be replaced, it is desirable to
verify correct operation of all circuits that could cause erratic readings.
T
ROUBLESHOOTING
Z
ERO
- S
UPPRESSED
R
ANGE
I
NSTRUMENTS
In troubleshooting an analyzer that has zero-suppressed ranges only, the use of a
zero-based range change kit is recommended. In the initial troubleshooting, the zero-
based range resistor module is installed temporarily, to provide a temporary zero-
based range. Analyzer readout may then be checked with 100% nitrogen as the
downscale standard gas and air (20.93% O
2
) as the upscale standard gas. Such
testing will also eliminate the effects of variations in barometric pressure and sample
pressure. These effects are sometimes difficult to diagnose on zero-suppressed
ranges.
7.2 CHECKOUT AT TEST POINTS ON CASE CIRCUIT BOARD
Initial checks are made at test points A, B, C and D on the Case Board. There are two
sets of these test points for accessibility. See Figure 7-1.
Test points A, B, C, and D permit connection to the photocells and the suspension of
loop. Locations of the test points within the detector circuit are as shown in Figure 7-2.
With zero gas flowing, connect a voltmeter across B and A; measure voltage and note
polarity, then. measure voltage from C or D to ground and note polarity. Check results
against table, Voltage Test Measurements.