NI 6601/6602 Calibration Procedure
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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 by picking up extra noise that can affect
measurements.
•
Maintain an ambient temperature of approximately 25 °C.
•
Keep relative humidity below 80%.
•
Use shielded copper wire for all cable connections to the device.
Use twisted-pair wire to eliminate noise and thermal offsets.
•
Allow a warm-up time of at least 15 minutes to ensure the
measurement circuitry is at a stable operating temperature.
Calibration Process
This section contains instructions for verifying the operation of the crystal
oscillator on the NI 6601/6602 devices using a stable clock source.
Verifying the performance of the oscillator on an NI 6601/6602 device
requires two counters on the NI 6601/6602 device—counters 0 and 1.
Counter 1 uses a stable clock as the source to generate a 50 ms single pulse,
which is applied to the GATE of counter 0. The 20 MHz timebase on the
NI 6601/6602 device, which is derived from the crystal oscillator, is the
SOURCE of counter 0. You will count the number of clock edges of the
20 MHz timebase that occur during the 50 ms single pulse and calculate the
frequency of the oscillator to determine if the device is within its
specifications. Figure 1 shows a simple diagram of the process.
Figure 1.
NI 6601/6602 Verification Process
50 ms
CTR 1
CTR 0
Stable Clock Source
20 MHz Timebase
Source
Source
Gate
Output
