TROUBLESHOOTING & REPAIR PROCEDURES
Model 300E Carbon Monoxide Analyzer
Instruction Manual
212
P/N 04288 Rev: A
11.5.7.
Motherboard
11.5.7.1. A/D Functions
The simplest method to check the operation of the A-to-D converter on the
motherboard is to use the Signal I/O function under the DIAG Menu to check the
two A/D reference Voltages and input signals that can be easily measured with a
Voltmeter.
§
Use the Signal I/O function (see Section 11.1.3 and Appendix A) to view the
value of
REF_4096_MV
and
REF_GND
. If both are within 3 mV of nominal
(4096 and 0), and are stable, ±0.5 mV then the basic A/D is functioning
properly. If not then the Motherboard is Bad
§
Choose a parameter in the Signal I/O function such as
SAMPLE_PRESSURE
,
SAMPLE_FLOW
,
CO_MEASURE
or
CO_REFERENCE
.
Compare these
Voltages at their origin (see Interconnect drawing 04215 and Interconnect
list 04216) with the voltage displayed through the Signal I/O function. If the
wiring is intact but there is a large difference between the measured and
displayed Voltage (±10 mV) then the Motherboard is bad.
11.5.7.2. Analog Outputs: Voltage
To verify that the Analog outputs are working properly, connect a voltmeter to the
output in question and perform an Analog Output Step Test as described in
Section 6.6.2.
For each of the steps, taking into account any offset that may have been
programmed into channel (see Section 6.5.1), the output should be within 1% of
the nominal value listed in the table below except for the 0% step, which should be
within 2 to 3 mV. If one or more of the steps fails to be within this range then it is
likely that there has been a failure of the either or both of the DACs and their
associated circuitry on the Motherboard.
Table 11-8: Analog Output Test Function - Nominal Values Voltage Outputs
Full scale Output Voltage
100mV 1V
5V
10V
Step %
Nominal Output Voltage
1 0
0
0 0 0
2 20 20
mV 0.2 1 2
3 40 40
mV 0.4 2 4
4 60 60
mV 0.6 3 6
5 80 80
mV 0.8 4 8
6 100 100
mV 1.0 5 10