DI-245 employs Open-Thermocouple-Detection (OTD), or TC Burnout Test,  feature when thermocouple inputs are selected, it helps to make sure the thermocouple wires are connected during the test. 

When thermocouple wires are no longer connected, DI-245 will sense it and indicate so on its WinDaq waveform chart. 

Note: This test is not fool proof. For example, if the thermocouple wires are separated, but are still submerged in some conductive media, such as conductive liquid, it will NOT be detected as open thermocouple (thermocouple burnout)

No doubt this feature helps to monitor the thermocouple connection, but this feature will affect the readings, especially in type SBR.

To demonstrate the difference, we conducted an accuracy test on a standard DI-245, using S-type thermocouple on all four channels, then OTD is removed and a comparison test was conducted to show the difference

Full test result in Excel spreadsheet
 

Here is the side-by-side comparison of accuracy plotting with and without OTD, and you can see when OTD is removed, the reading is much much better

Conclusion, if very accurate temperature measurement is required, contact DATAQ on how to remove the OTC circuit

Last update: 08/12/14

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