IOtech DaqBoard/3000USB Series User Manual Download Page 61

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Calibration 4

The DaqCal.exe calibration utility does not support DaqBoard/3000USB Series
boards at present. Please contact the factory for the latest calibration information
concerning these products.

Every range of a DaqBoard/3000USB board is calibrated at the factory using a digital NIST traceable
calibration method. This method works by storing a correction factor for each range on the unit at the time
of calibration. The user can adjust the calibration of the board while it is installed in the acquisition system
without destroying the factory calibration. This is accomplished by having 3 distinct calibration tables in
the on-board EPROM.

The user can select any of the three cal tables provided [factory, user, or self-cal tables] by API call or from
within software. Self-cal

can be performed automatically via the included software and without the use of

external hardware or instruments. Self-cal derives its tracebility through an on-board reference which has a
stability of 0.005% per year.

Note that a 2-year calibration period is recommended for /3000USB Series boards.

Using a Temperature Calibrator

DaqBoard/3000USB boards 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

C, or if the product is near or outside its 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 /3000USB Series board with the same
type thermocouple wire and connector that is used in normal testing. The calibrator then generates and
supplies a voltage corresponding to that which would be generated by the TC type [at the associated
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 board reads 0.3

C, then an adjustment of

minus

0.3

C is required. That is, the adjustment value is determined by subtracting the board’s reading from the

calibrator setting.

To implement the adjustment in DaqView:

Ensure that the acquisition process is turned off.

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.

Click on the down arrow and select the “mx+b” option. This option allows post-acquisition
mathematical manipulation.

For the example adjustment, enter -0.3 for “b.” The channel under calibration will now
read 0

Note that this adjustment is a mathematical operation only, and in no way alters the board’s hardware
calibration. Moreover, it operates on a per channel basis, with the settings for a given channel having no
influence on any other channels.

DaqBoard/3000 Series User’s Manual

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Calibration 4-1