Probably what John said, the trigger level, or your vibration is too high and shaking the sensor... Or you are holding it by hand?
For balancing and speedvue you must likely always need to use a reflective tape or a strong pulse signal from the shaft and set the trigger level
Try this to search for the correct trigger level.
https://www.emerson.com/docume...els-ams-en-39100.pdf
Too much vibration put your sensor on a different surface, it has a very long range you will not have any terribly