Understanding Hysteresis (ELVIS RIO Control Toolkit)

LabVIEW 2016 ELVIS RIO Control Toolkit Help

Edition Date: June 2016

Part Number: 376300A-01

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Hysteresis, also known as window size, adds a window above or below the trigger level. Hysteresis reduces false triggering due to noise or jitter in the signal.

When you use the Register Analog Input Interrupt VI or the Interrupt Express VI to generate analog input interrupts, both of these VIs use a 0.02 V hysteresis to avoid false interrupt registration. The way this hysteresis works depends on whether you register an interrupt on the falling edge or rising edge of the analog input signal, as described in the following table.

Type Description
Analog Falling Edge The VI registers an interrupt when the signal starts or rises above Threshold plus hysteresis and then drops below Threshold.
Analog Rising Edge The VI registers an interrupt when the signal starts below Threshold minus hysteresis and then crosses above Threshold.

Use the following figure to understand when the VI registers analog-falling-edge interrupts.

The following list describes important details about the previous figure:

The signal rises above Threshold plus hysteresis. When the signal value drops below Threshold, the VI registers an interrupt.
The VI does not register any interrupt, because the signal stays below Threshold plus hysteresis since the VI last registered an interrupt.
The signal rises above Threshold plus hysteresis. When the signal drops below Threshold, the VI registers another interrupt.

Use the following figure to understand when the VI registers analog-rising-edge interrupts.

The following list describes important details about the previous figure:

The VI registers an interrupt when the signal value rises above Threshold.
The VI does not register any interrupt, because the signal stays above Threshold minus hysteresis since the VI last registered an interrupt.
The signal drops below Threshold minus hysteresis. When the signal crosses above Threshold, the VI registers another interrupt.

Related Information

Interrupt Express VI

Register Analog Input Interrupt VI

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