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National Instruments Corporation
2-1
2
Using the SCXI-1530/1531
This chapter describes how to take measurements using the
SCXI-1530/1531. The two major modes of operation, multiplexed and
parallel, are described, along with how to connect signal sources to the
SCXI-1530/1531. Calibration is also described.
Accelerometer Design
A typical current-excited accelerometer is shown in Figure 2-1. Its main
components are the accelerometer case, a free-floating seismic mass, and a
piezoelectric crystal between the case and mass. When the system
undergoes an acceleration, the crystal is either stretched or compressed.
This strain on the crystal induces a charge difference between its surfaces.
This charge difference is detected by a charge-sensitive amplifier and is
converted into a voltage signal. The amplifier is energized by a constant
current source. As crystal acceleration varies, the output impedance
varies to create the voltage signal in the current path. Therefore, the
current-excited accelerometer is both excited and read from the same
two connections, resulting in a simple 2-wire system.