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Troubleshooting & Repair Teledyne API – Technical Manual - Model 300E Family CO Analyzers
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13.5.7. MOTHERBOARD
13.5.7.1. 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.
3. Use the Signal I/O function (see Section 13.1.3 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.
4. 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, P/N 04215 and interconnect list,
P/N 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.
13.5.7.2. Test Channel / Analog Outputs Voltage
The ANALOG OUTPUT submenu, located under the SETUP MORE DIAG menu is used to verify that the
M300E/EM Analyzer’s analog outputs are working properly. The test generates a signal on functioning outputs
simultaneously as shown in the following table.
Table 13-10: Analog Output Test Function - Nominal Values Voltage Outputs
FULL SCALE OUTPUT OF VOLTAGE RANGE
(see Section 7.4.2)
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
For each of the steps the output should be within 1% of the nominal value listed in the table below except for the
0% step, which should be within 0mV ±2 mV. Make sure you take into account any offset that may have been
programmed into channel (see Section 7.4.5).
If one or more of the steps fails to be within these ran
ges, it is likel
y that there has been a failure of either or both
of the DACs and their associated circuitry on the motherboard. To perform the test connect a voltmeter to the
output in question and perform an analog output step test as follows:
04288D DCN5752