Cpu; Communications - Teledyne T200 Operation Manual

Troubleshooting & Service
12.7.7.3. VACUUM PRESSURE SENSOR CHECK
12.7.7.4. O FLOW SENSOR CHECK
3

12.7.8. CPU

12.7.9. RS-232 COMMUNICATIONS
12.7.9.1. GENERAL RS-232 TROUBLESHOOTING
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Teledyne API – T200 NO/NO2/NOx Analyzer Operation Manual

If this voltage is out of range, then either pressure transducer S1 is bad, the board is
bad or there is a pneumatic failure preventing the pressure transducer from sensing
the absorption cell pressure properly. Replace the PCA.

Measure the pressure on the inlet side of S2 with an external pressure meter.

Measure the voltage across TP5 and TP1.

Evaluate the reading in the same manner as for the sample pressure sensor.

Measure the voltage across TP3 and TP1.

With proper flow (80 cc
approximately 2V ± 0.25 (this voltage will vary with altitude).

With flow stopped (photometer inlet disconnected or pump turned OFF) the
voltage should be approximately 1V.

If the voltage is incorrect, the flow sensor S3 is bad, the board is bad (replace
the PCA) or there is a leak upstream of the sensor.
There are two major types of CPU board failures, a complete failure and a failure
associated with the Disk On Module (DOM). If either of these failures occurs, contact
the factory.
For complete failures, assuming that the power supplies are operating properly and the
wiring is intact, the CPU is faulty if on power-on, the watchdog LED on the
motherboard is not flashing.

In some rare circumstances, this failure may be caused by a bad IC on the
motherboard, specifically U57, the large, 44 pin device on the lower right hand side
of the board. If this is true, removing U57 from its socket will allow the instrument to
start up but the measurements will be invalid.

If the analyzer stops during initialization (the front panel display shows a fault or
warning message), it is likely that the DOM, the firmware or the configuration and
data files have been corrupted.
Teledyne API's analyzers use the RS-232 communications protocol to allow the
instrument to be connected to a variety of computer-based equipment. RS-232 has been
used for many years and as equipment has become more advanced, connections between
various types of hardware have become increasingly difficult.
manufacturer observes the signal and timing requirements of the protocol very carefully.
Problems with RS-232 connections usually center around 4 general areas:

Incorrect cabling and connectors. See Section 3.3.1.8, Figure 3-13 for connector
and pin-out information.

The BAUD rate and protocol are incorrectly configured. See Section 6.2.2.
3
/min through the O generator), this should be
3
Generally, every
06858E DCN7057