Measurement Computing WBK40 - Manual (Page 20)

DBK46 is installed at the factory. To verify that a DBK46 is installed, simply check the acquisition
software’s Analog Output Window for the presence of DAC0, DAC1, DAC2, and DAC3.
Note that the DBK46 does not require any setup in software.
Reference Note:
In regard to the out-of-the-box software and analog output channels, refer to the
WaveView
Document Module. However, as of this document date, the WaveView graphical user
interface (GUI) does not specifically address WBK40 or WBK41.
Using a Temperature Calibrator
The thermocouple modules provide accurate and repeatable temperature measurements across a wide range
of operating conditions. However, all instrumentation is subject to drift with time and with ambient
temperature change. If the ambient temperature of the operating environment is below 18
°C or above
28 °C, or if the product is near or outside its one-year calibration interval, then the absolute accuracy may
be improved through the use of an external temperature calibrator.
A temperature calibrator is a temperature simulation instrument that allows selection of thermocouple type
and temperature. For proper operation, it must be connected to the WBK40, WBK41, or DBK84 with the
same type thermocouple wire and connector that is used in normal testing. The calibrator then generates
and supplies a voltage to the module. The supplied voltage corresponds to that which would be generated
by the chosen thermocouple type at the selected temperature.
The temperature selected on the calibrator will be dictated by the nature of normal testing. 0 °C is usually
the best choice. Calibrators are the most accurate at this setting, and the connecting thermocouple wire will
contribute very little error at this temperature. However, if the dynamic range of the normal testing is, for
example, 100
°C to 300°C, a selection of 200°C may give better results. In either case, the level of
adjustment is determined by comparing the unit reading to the selected calibrator temperature. For
example, if the calibrator is set to 0
°C output, and the unit reads 0.3°C, then an adjustment of –0.3°C is
required. That is, the adjustment value is determined by subtracting the device reading from the calibrator
setting.
To implement the adjustment in DaqView:
1. Ensure that the acquisition process is turned off.
2. Click on the cell in the Units column for the channel that is connected to the calibrator.
The engineering units pull-down menu above the grid becomes active.
3. Click on the down arrow and select the “mx+b” option. This option allows post-acquisition
mathematical manipulation.
4. For the example adjustment, enter –0.3 for “b.” The channel under calibration will now
read 0 °C.
Note that this adjustment is a mathematical operation only, and in no way alters the hardware
calibration of the product. Moreover, it operates on a per channel basis, with the settings for a
given channel having no influence on any other channels.
Reference Notes:
For Additional mx+b information, refer to the mx_plus_b.pdf document, which is included on
the data acquisition CD.
pg. 20, WBK40 & WBK41 926896 Thermocouple and Multifunctional Modules