Measurement-computing Data Acquisition Systems rev.10.4 Manuel d'utilisateur télécharger pdf (Page 177)

Returns

DerrTCE_TYPE Invalid thermocouple type

DerrTCE_PARAM Parameter out-of-range

DerrNoError No error

For more details on error messages refer to the Daq Error Table.

Function Usage

For all functions of the form daqCvt..., raw data to be converted must be unsigned

(i.e., the dafUnsigned value must be set using the daqAdcSetScan function).

For T/C and RTD conversion, users of Daq/2000 Series devices* and/or Daq PC Cards must

be sure that the main unit is using ten volt range gains settings, either unipolar (0 V to 10 V)

or bipolar (-5 V to +5 V).

See the “T/C Gains Settings” section in the daqCvtTCConvert function entry for the

appropriate settings.

* Daq/2000 Series devices include DaqBook/2000 Series, DaqScan/2000 Series, DaqLab/2000

Series, and DaqBoard/2000 Series devices.

Note: The following example assumes a CJC position of “0” and a Channel Zero position of “1.”

The position of these channels is device dependent. Refer to your device-specific hardware

documentation to determine the appropriate position of these channels for your application.

The daqCvtTCSetup function is used to set the values required to convert raw thermocouple (T/C) data to

data on a Celsius scale. It must be follwed with the daqCvtTCConvert function to actually convert the data.

For convenience, both setup and conversion can be performed at once by daqCvtTCSetupConvert. All of

the T/C conversion functions (i.e., functions of the form daqCvtTC…)can convert several consecutive scans

of data in a single invocation.

The cjcPosition parameter determines the positon of the CJC reading in the scan group. Each scan of

temperature data must include a reading of the CJC signal on the expansion board to which the thermocouples

are attached. If zero compensation is being used, then the first two scans in each group are reserved for zero

compensation data, and the CJC scan must follow immediately thereafter. The illustration below shows a how

a typical T/C acquisition with zero compensation would collect data:

Programmer’s Manual 908494 Daq API Command Reference 4.3-51

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Measurement-computing Data Acquisition Systems rev.10.4 Manuel d'utilisateur Page 177