How to interpret analog sensor output

Other Hardware Sensors
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Hi, I have an analog triaxial accelerometer ( 830M1 ) on a vibration rig connected to a "labjack", which is as I understand, functionally the same as an Arduino.

I have successfully been able to gather data in the form of a voltage output, meaning that when the sensor experiences vibration, the voltage increases in the xyz-axes. However I am not sure how to translate this voltage into an amplitude.
The datasheet does not provide a scaling equation that allows me to find the amplitude as far as I can tell.
https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet830M1_Triaxial_AccelerometerA3pdfEnglishENG_DS_830M1_Triaxial_Accelerometer_A3.pdfCAT-EAC0023

An example output is: 1.510429, 1.071990, 1.098840 (volt) (one output for each axis)

I hope that made sense, any input would be appreciated, thank you.

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Can it be programmed with the Arduino IDE. If not, then it is not equivalent to an Arduino.

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What was the measurement range to acquire those readings?

Use the sensitivity for that range to calculate the answer.

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Never heard of that. Can you post a link to the specs?

You could calibrate it by placing it on a stationary, horizontal surface. Whatever it's voltage readings are, they must represent 9.81m/s² or 1g.

By orientating the sensor with its x, y & z axes pointing normally to the surface and making a note of the readings, you can calibrate it to give the correct readings.

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Ahh so if the the sens is 50 mV/g then a 1 volt signal equals 20g amplitude. Makes sense, thanks. However I am confused about the base values. Why does the sensor output 1 volt when it is subject to 0 forces except gravity?

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I must mention that electronics is not really my field

When stationary, the signals usually fluctuate around 1.1 for 2 of the axes, though one of the axes sits around 1.5 instead. When undergoing vibration, the values start to flutuate +-0.2 . Assuming then that 1G = 1.1V then this is a little strange I believe the vibrations to be significant enough to provide more of an impact than just around .2G

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The zero reading must be offset so that the sensor can measure and output for negative Gs, but keep the output signal positive. So, for instance, a plus-minus 25 g sensor with a 5V full scale output will output 2.5V at 0g, 5V at +25 g and 0V at -25g.

One axis will always have 1g due to gravity, the other 2 are at 0g. Most sensors will have an inherent output offset at 0. You can calibrate for that like @PaulRB describes.

1 Like
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Such disagreement is typical for an uncalibrated accelerometer. The min/max calibration method described in the link below is usually good enough: Calibration and Programming | Adafruit Analog Accelerometer Breakouts | Adafruit Learning System

NOTE: the accelerometer data sheet indicates that the output is bipolar, and swings from -1.25V to 1.25V. An Arduino cannot measure negative voltages and the analog input may be destroyed if you try. What does Labjack do with negative voltages?

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Not an Arduino!

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Good question, when I ran the sensor it never got anywhere close to negative values so I couldn't tell you. It does seem to support bipolar outputs though.

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True, but my question was more about the sensor itself and how to read the data and this is the only forum I know with a section dedicated to sensors.

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Does Labjack even support bipolar outputs, and negative voltages?

Get out your multimeter and verify that the sensor is working as the datasheet indicates. Any vertical axis should read positive 1 g when pointing up, and negative 1 g when that axis is pointing down.

Until you completely understand how the sensor works, and how to read the output, there is not much sense in going further.

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