I have a tilt sensor that acts sort of like a potentiometer. It is an electrolytic sensor that acts sort of like a balance. One side increases in voltage while one side lowers voltage. The sum of both voltages must add up to 4VAC.

the sensor has a nominal scale factor of 0.174mV/degree

When I put the sensor on a surface I take two voltage measurements

One side angle = (SideAvoltage - 2.00) / 0.174

Other side = (2.00 - SideBvoltage) / 0.174

I'm looking for a way to combine these into one equation so I can calculate magnitude and direction of the angle.

Sensor Datasheet:CG-57S http://www.spectronsensors.com/datasheets/SDS-105-2704.pdf

Would it be sort of a vector sum?

  • \$\begingroup\$ Can you provide a manufacturer's reference to it for more detail? \$\endgroup\$
    – Andy aka
    Oct 31, 2013 at 8:09
  • \$\begingroup\$ Added datasheet \$\endgroup\$ Oct 31, 2013 at 12:02
  • \$\begingroup\$ Not very clear what the problem is: Would the difference between the two voltage readings not give you the combined tilt between the two alignments? V = ( Va + (- Vb) ) / 2 can then be used to calculate the average sensed angle, accounting for machining tolerances between alignment A and alignment B. Sign of V (positive or negative) indicates direction. \$\endgroup\$ Oct 31, 2013 at 12:55
  • \$\begingroup\$ What do you mean by "magnitude" and "direction" of an angle? Vectors have magnitude and direction, but angles are not vectors. There is no such thing as "a little bit 90 degrees" and "a lot 90 degrees". \$\endgroup\$
    – Phil Frost
    Oct 31, 2013 at 14:39

1 Answer 1


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(Source: figure #5 from here.)

As you've said both outputs add up to the AC excitation voltage. But you read the voltage between the "cursor" (thinking in the sensor as a sort of potentiometer) and one of the outputs.

The outputs are opposite, one output doesn't give information not available at the other output, just choose one.

And the, your output reading would be of the form:

angle = k Vo

where k is the transduction constant (be careful, its dependant on the AC excitation). The more amplitude, the more tilt. Direction (tilt side) is in the sign (phase).

  • \$\begingroup\$ I see so reading one side will give me the angle I need. I don't have to read both to get a single result angle. Yes the scale factor is 0.435mV/degree/V excitation at 22 C So I can measure phase to see what the direction is on this sensor? \$\endgroup\$ Oct 31, 2013 at 18:03

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