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Trend in analog tachometer signals can influence where you set the threshold to locate tachometer pulse positions. Use the OAT Detrend Analog Tacho Signal VI to remove the trend from a signal. The detrend level can be between zero and one, according to the trend property in the tachometer signal. As the value of the detrend level increases, the trend value becomes closer to the value of the analog tachometer signal. When the detrend level approaches one, the trend converges with the original analog tachometer signal.

The following front panel shows the result of using the OAT Detrend Analog Tacho Signal VI to remove the trend from an analog tachometer signal.

In the previous front panel, the white line is the original signal with a sine trend. The scale of this line is –6 to 6, as shown on the left-hand y-axis. The red line is the detrended signal. The detrended signal scale is –1 to 1, as shown on the right-hand y-axis. You can set a uniform threshold to detect pulse instances in the detrended signal, whereas you cannot set a uniform threshold with the original signal.