6703/6704 Calibration Procedure
6
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Recommended Test Equipment
To perform calibration, you need a high-precision voltage and current
measuring device. This device should be at least 10 ppm (0.001%) accurate.
National Instruments recommends that you use the Hewlett-Packard
3458A DMM for calibration.
If you do not have the exact instrument, use the previously mentioned
accuracy requirements to select a substitute calibration standard.
If you do not have custom connection hardware, you may need a connector
block such as the National Instruments CB-68 and a cable such as the
SH6868-D1. These components give you easy access to the individual pins
on the 68-pin board I/O connector.
Environmental Issues
Be aware of these connection issues and environmental concerns:
•
Keep connections to the DAQ device as short as possible. Long cables
and wires can act as antennas by picking up extra noise that would
affect calibration.
•
Maintain the temperature between 18–28 °C.
•
Keep relative humidity below 80%.
•
Use shielded copper wire for all cable connections to the device. It is
often advisable to use twisted-pair wire to eliminate noise and thermal
offsets.
•
Allow a warm-up time of at least 15 minutes for PXI/PCI/AT bus
devices and 30 minutes for PCMCIA cards to ensure that the
measurement circuitry is at a stable operating temperature.
Calibration Process
To calibrate your device, follow these main steps:
1.
Verify the existing operation of the board. This step, which is covered
in the
Verifying Your Board’s Operation
section, allows you to
confirm that the board was in specification prior to calibration.
2.
Perform an external calibration that adjusts the board calibration
constants with respect to a known voltage source. This step is
described in the
3.
Perform another verification to ensure the board is operating within its
specifications after calibration.
Note
This procedure uses NI-DAQ function calls.
