Predictive maintenance sensor acceleration units

I’m having some trouble determine the units for a PM sensor coupled to an MQTT gateway. Based on the documentation, I would have assumed the units are mg. But it doesn’t line up with the data.

My sensor placed so that the z axis is oriented axially to the rotation of a blower motor. The axis of rotation of the motor is vertical. See the attached image.

This is an example of data when the motor is not running.

This is an example of data when the motor is running:
2020-02-05 19:30:50.353978,/raw/mqtt/sensor_data/decoded,{“data”:{“transmission_count”:49,“battery_level”:3.29406,“type”:50,“node_id”:0,“rssi”:100,“rms_x”:14139.2,“rms_y”:6717.4,“rms_z”:2505.1,“max_x”:15247.5,“max_y”:0,“max_z”:4809.2,“min_x”:0,“min_y”:-8842.5,“min_z”:-607.5,“Vibration_Celsius”:29,“Thermocouple_Celsius”:24.87,“Current”:1.331},“id”:“00:13:A2:00:41:A8:64:6B”}

In this case max_z increased significantly as expected. That makes sense.

What I don’t understand, though is, why the resting max_z is 2583.9. I can understand why the value might not be exactly zero, but 2 g’s is a little difficult to believe. Furthermore, y is vertical and max_y is zero in both cases.

So something doesn’t seem correct here. I’m assuming my interpretation here is wrong. What are the units supposed to be and do the values make sense?

Note that this image is oriented correctly, with the wire going down towards the ground.

Did you press reset after installing the sensor ?
was the machine off when sensor was installed ?

at the boot sensor self calibrates and for best results the machine should be off during calibration.


I didn’t press reset after installing the sensor, but I did start it before attaching it, and I attached it to non-running equipment.

reset the sensor once its installed on the machine.

RMS – its the avg data during the sampling interval

Max – its the max vibration value during the sample interval

The sensor output value is in mg.
please check sensor manual table 3 for more info.