Issue Details
When reviewing the Trend Graph in InsightCM, hundreds of data events appear as captured while the machine was in the Off state, and those events show velocity readings of several thousand revolutions per minute (RPM). Because the system keeps acquiring and storing these events, they consume a substantial amount of the available disk space.
Is there a way to prevent these unwanted data events from being captured while the machine is off?
Solution/Procedure
A vibration monitoring system determines whether a machine is running or stopped based on the speed measurement provided by the tachometer for this specific case. If the tachometer measurement is incorrect, the system interprets the machine as running while it is actually off, and triggers data acquisition events that should not occur.
The most common cause is an incorrectly configured voltage hysteresis on the tachometer channel. Tachometer voltage hysteresis is a built-in voltage difference, or deadband, between the input signal level that triggers a pulse detection event and the level required to reset it. When this deadband is too narrow, signal noise is counted as pulses and produces false speed readings.
To correct the behavior:
1. In InsightCM, navigate to Asset Configuration > Tachometer > Properties tab.
2. Locate the Tachometer Hysteresis (volt) parameter and review its current value.
3. Increase the Tachometer Hysteresis (volt) value so the deadband is wide enough to reject signal noise. This parameter typically ranges from 0.1 V to 1.0 V.
4. Update Configuration and allow the machine to complete another off-state cycle.
5. Return to the Trend Graph and verify that no new data events are captured while the machine is in the Off state.
6. If false data events are still being recorded, adjust the Tachometer Hysteresis (volt) value again within the typical range and repeat the verification after the next off-state cycle.
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