Digital Tachometer Signals

A counter device typically operates at a much higher sampling rate than the analog input channels used to acquire sound and vibration signals. The counter device also can detect pulses directly without using additional VIs to set a threshold for the tachometer signal. For these reasons, a counter device is ideal for acquiring tachometer signals at high speeds or tachometer signals that encoders generate. A digital tachometer signal is usually more accurate than an analog tachometer signal.

Digital tachometer signals must be transistor-transistor logic (TTL) compatible. Acquiring a digital tachometer signal requires additional devices, such as a counter or timer device and a signal conditioning device, to condition the tachometer signal for TTL compatibility.

You also can acquire a digital tachometer signal using a multi-function reconfigurable I/O device, such as the NI PXI-7831R. This kind of device allows you to use the LabVIEW FPGA Module to configure the digital lines as inputs, outputs, or counters. You also can perform tachometer signal conditioning with the device or configure a 64-bit counter.