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If thermistor resistance(s) are within the proper range, check the temperature linearzation
circuits on the DC Power Supply Board as described in Section 10.6.4.
If temperature sensor readings appear accurate but control temperatures are not being
maintained at their proper value, check the operation of the heaters as follows:
1. Observe the indicator LED's on the Power Supply Module and confirm
that the red (right-most) LED is lit, and that the "CEL HTR" LED is lit or
cycling (turning off and on). If these indicators are not correct, it is
probably that the Power Supply Module, or the V/F Board is at fault.
Check as described in Sections 10.2 and 10.6.3.
2. Unplug the heater element from Power Supply Module and confirm that
115 VAC is present. If 115 VAC is present, the heater element has failed
and should be replaced.
WARNING
HAZARDOUS VOLTAGES PRESENT - USE CAUTION!
10.6.3 Checking the V/F card
A schematic and physical diagram of the V/F card are shown on Drawings 514 and 515
in Appendix C. The V/F is a multi-function I/O card which connects to the
micro-processor via a STD Bus interface, and acts as the primary I/O interface between
the micro-processor and the rest of the analyzer. All functions of the board are performed
under control of the micro-processor.
The primary functions of the board can be divided into three areas:
- 16 Channels of Multiplexed Analog input to an Analog to Digital converter
- 4 independent Digital to Analog converters
- 32 Digital I/O Lines configured as 24 outputs and 8 inputs
The following sections describe each of these functional areas.
10.6.3.1 Analog Inputs
16 Analog channels (0-5 VDC) are multiplexed under micro-processor control by IC U26
and transmitted via buffer amp U29 to the V/F converter section of the board for A-D
conversion.
P/N 02163G1 Teledyne API Model 300 CO Analyzer Instruction Manual - Page 92