Dmm Operation; Warm-Up; Choosing A Reading Rate - National Instruments DAQMeter DAQCard-4050 User Manual

DMM Operation

Warm-up

Choosing a Reading Rate

© National Instruments Corporation
This chapter describes how to use your DAQMeter DAQCard-4050 and
includes operation tips on taking voltage, resistance, diode, and current
readings.
Measurements taken with the DAQCard-4050 change with temperature.
These changes are called thermal drifts or temperature coefficients. The
DAQCard-4050 temperature coefficient specifications are listed in the
Accuracy sections in Appendix A, Specifications. PCMCIA slots,
especially those in many notebook computers, can warm up a card
significantly above the ambient temperature. Therefore, measurements
made immediately after inserting the DAQCard-4050 or powering up
the computer can differ significantly from measurements made after the
DAQCard-4050 has fully warmed up.
To minimize the effects of thermal drift and ensure the specified
accuracies, let the DAQCard-4050 warm up for at least 30 seconds after
power-up before taking measurements. To maximize the relative
accuracy of measurements, take all measurements after the
DAQCard-4050 has had a chance to fully warm up in the computer,
about 15 minutes.
In all measurement ranges and modes of the DAQCard-4050, there
are three possible reading rates available for use—10, 50, and
60 readings/s. The reading rate is the rate at which a new measurement
is taken. In addition to the measurement speed, the selection of the
reading rate affects the filtering, and thus the noise level, of
measurements.
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