There are three sets of diagnostics information recorded in tables on Campbell Scientific data loggers for Measurand ShapeArray projects that are vital to diagnosing issues with the instrument. Some information can also be inferred by examining the raw data recorded from the ShapeArray. When diagnosing ShapeArray issues, Measurand examines information from the following tables on the data logger:
- LOGGER_DIAGNOSTICS – Records the voltage and temperature at the data logger
- SAA_DIAGNOSTICS – Records the voltage, current, and temperature at the top segment of the ShapeArray, known as the SAATop.
- SERIAL_ERRORS – Records the number of communication issues that occur when trying to get readings from the ShapeArray.
- SAA#_DATA – Records the raw data readings from the ShapeArray
The values of primary diagnostic interest are outlined in the table below.
|Expected Values||Voltages > 10.5 V|
Voltages < 17.0 V
|Voltages > 10.5 V|
Voltages < 17.0 V
|Current consistent with factory measured values||0 COM or CRC errors|
In the LOGGER_DIAGNOSTICS table, the voltage recorded at the data logger is helpful when evaluating the health of a ShapeArray. The data logger and ShapeArrays are typically powered from the same power source and low power at the data logger is often a good indicator of problems with the power source in the data acquisition system.
Underpowered ShapeArrays are identified by the reviewing the diagnostics data recorded in the SAA_DIAGNOSTICS table on the data logger. Although the power required for a ShapeArray to properly operate varies based on the number segments in the instrument, underpowered ShapeArrays are typically identified by instances of the following voltages read at the top segment of the instrument (the SAATop):
- Voltages below 10.5 V
- Voltage above 1,000 V
Voltages readings above 1,000 V typically occur when there is only enough power being provided to activate the circuitry in the ShapeArray but not enough power to take a valid measurement of the actual voltage being provided. In this case, the actual voltage being supplied is much lower than 10.5 V.
We also examine the current readings recorded in the SAA_DIAGNOSTICS to see if the power being drawn is consistent with values measured for the instruments at the time of production. Normal current values should be within 10-15% of the factory measured current. Only currents associated with normal voltage readings are examined. Current recorded for readings with low voltages are often not truly representative of the current being drawn.
ShapeArrays that are not properly powered can exhibit erroneous data in a number of ways. In some cases, an underpowered ShapeArray will return zeros for its raw data readings or invalid raw data readings. In some cases, a ShapeArray that is improperly powered can return raw data readings that appear valid but are not truly representative of the tilts of their respective segments. For this reason, measurements being returned from an underpowered ShapeArray cannot be trusted as true measurements.
The SERIAL_ERRORS table on the data logger record instances of communication issues with the ShapeArray. This table tracks instances of unresponsiveness from segments within the instrument (COM errors) and instances where the data returned from a segment fails a cyclical redundancy check (CRC errors).
In the SAA#_DATA table, raw ShapeArray data is recorded. This data consists of a number of counts returned from the X-, Y-, and Z-axis sensors in each segment of the instrument. These raw data counts correspond to the physical tilt of the segment in each specified axis relative to gravity. Raw data counts should be within a range of 10,000 to 60,000 for a normal working instrument.
When troubleshooting unexpected behavior in ShapeArray data, we examine the raw data collected from the data logger in the SAA#_DATA tables. The SAACR_DataChecker utility included in the Measurand SAASuite software allows raw ShapeArray data to be presented graphically. This utility displays the raw data counts using a range of colored blocks that align to the limits of valid readings (10,000 to 60,000). Invalid data is quickly visible in this tool as it appears as black blocks. More information about using SAACR_DataChecker to examine raw ShapeArray data is available in the Using SAACR_DataChecker support article.