Trans-Cal Industries

    Common Altitude Digitizer Problems

    Troubleshooting Flow Charts

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Troubleshooting Altitude Digitizers


There is no substitute for common sense and experience. The flow charts, accessed through links on this page, assume a basic understanding of electronics and the function of the digitizer within the pitot-static and electrical system of an aircraft. Please exercise caution when troubleshooting altitude digitizers. These charts are NOT all encompassing. Based on failures reported in the field and units returned to TCI, these flow charts are intended to provide a starting point for localization of problems in the altitude digitizer and interconnected equipment. They are intended for troubleshooting Trans-Cal devices only, and should not be construed as to apply to other manufacturer’s devices.

PLEASE NOTE: Trans-Cal Industries, Inc. does not repair Model SSD120-(XX)N-(XXXX) Altitude Digitizers. If a unit has failed within the warranty period, or outside of that period, the remedy is to replace the unit.


In some cases, specialized test equipment and the expertise required to operate it may be necessary as listed below:

CAUTION!

Improper operation of some test equipment may damage sensitive instrumentation in the aircraft. Test equipment should be operated only by personnel who are qualified and thoroughly familiar with the test and certification of aircraft systems.

The equipment listed below may or may not be required depending on the needs of the particular installation.

  1. Pitot-Static Test set capable of exercising the static system over the operating range of the digitizer.
  2. Volt/Ohm Meter
  3. Transponder ramp test set
  4. ATS-400 Altitude Digitizer Test Set or equal
  5. ECP-100 Encoder Calibration Programmer or equal
  6. IBM PC with serial data capture software or equal

Additional troubleshooting resources include the FAQ section of the TCI website found here. Included on this webpage is a “Known Compatibility Issues” section.

Complete Document (pdf) - Basic Troubleshooting Flow Charts Model SSD120-(XX)N-XXXX Document Number 882239 Rev. A.

 

Common Problem Description
Digitizer leaks in excess of 100'/min. Click here for troubleshooting process. Leak Troubleshooting
Digitizer provides no output. Click here for troubleshooting chart.
Basic Troubleshooting Flow Chart
Digitizer outputs approximatly 2300' at all times. Click here for troubleshooting chart.

Non-Sequential Count Troubleshooting Flow Chart

Digitizer output is non-sequential. Click here for troubleshooting chart.

Non-Sequential Count Troubleshooting Flow Chart

Digitizer does not transmit serial data. (Both channels transmitting the same baud rate/message) Click here for troubleshooting chart.

Serial Communication Troubleshooting Flow Chart

Digitizer does not transmit serial data. (Transmitting two different baud rates/messages) Click here for troubleshooting chart.
Dual Serial Communication Troubleshooting Flow Chart
Digitizer output slowly ascends/descends without any input pressure change, or reads -1100 at all times. Click here for troubleshooting chart.
Slow Ascend/Descend/-1100 Troubleshooting Chart

 

 

 

 

Trans-Cal Industries, Inc., 16141 Cohasset Street, Van Nuys, CA 91406-2908 Phone: (818)787-1221

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