NI VirtualBench Calibration Procedure | © National Instruments | 5
Test Conditions
Follow these guidelines to optimize the equipment and the environment during calibration:
• Keep connections to the device as short as possible. Long cables and wires act as antennae,
picking up noise that can affect measurements.
• Use a USB connection between the PC and VirtualBench.
• Verify that all connections to the device, including front panel connections, are secure.
• Keep relative humidity between 10% and 80% noncondensing.
• Allow a warm up time of at least 30 minutes to ensure that the VirtualBench is at a stable
operating temperature.
• Plug the VirtualBench, PC, and the test equipment into the same power strip to avoid
ground loops.
• Verification limits are defined assuming the same test equipment is used during verification
and adjustment.
•
(Oscilloscope, FGEN, and DC Power Supply Procedures) Maintain an ambient
temperature of 23 ±5 °C. The device temperature will be greater than the ambient
temperature.
• (DMM Procedure) Maintain an ambient temperature of 23 ±1 °C. The device temperature
will be greater than the ambient temperature.
• (DMM Procedure) Clean any oxidation from the banana plugs on the Fluke 5440 cables
before plugging them into the binding posts of the calibrator or the banana plug connectors
on the VirtualBench. Oxidation tarnishes the copper banana plugs so that they appear dull
rather than shiny and leads to greater thermal EMF.
• (DMM Procedure) Keep the blue banana plugs on the Fluke 5440 cables connected to the
V GUARD binding post of the calibrator at all times.
• (DMM Procedure) Prevent the cables from moving or vibrating by taping or strapping
them to a nonvibrating surface. Movement or vibration causes triboelectric effects that can
result in measurement errors.
• (DC Power Supply Procedure) Use shielded copper wire for all cable connections. Use
twisted-pair, shielded wire to reduce measurement error in noisy environments.
Digital Multimeter (DMM) Calibration Procedure
This section contains the verification and adjustment procedures for the DMM on the
VirtualBench. The calibration process includes the following steps:
1. DMM Initial Setup—Set up the test equipment.
2. DMM Verification—Verify the existing operation of the instrument. This step confirms
whether the instrument is operating within its specified range prior to adjustment.
3. DMM Adjustment—Perform an external adjustment of the instrument that adjusts the
calibration constants with respect to standards of known values.
4. DMM Re-Verification—Repeat the verification procedure to ensure that the instrument is
operating within its specifications after adjustment.
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