Absolute Rotary position -out of the box


Thread Starter


I need a device which will output a rotary position such as -potentiometer, abs. encoder, resolver. It must be consistent from one unit to the next within 15' so that I do not need to do a setup or calibration.

My product has a shaft that will rotate to three positions which are controlled by open loop, hard stop. My customers need to know where the shaft is at any time. For ease of product assembly, and for ease of service years down the road, I want the rotary measuring device to be replaceable without needing calibration or setup. After accounting for mechanical position tolerance of my mount, I want the rotary device to measure within 15' of the previous rotary device. This must be an absolute device -no homing routine. If the device needs two parts -such as a potentiometer and a DAQ, that is acceptable provided neither needs setup or calibration to hit the 15' and they are not "paired" -that is my customer can pop in any other pot or DAQ (of the same part number) and still be within 15'. Repeating: I have already accounted for the error contribution of my mount, I want the consistency of the device (from one to the next)to not add more than 15'.

James Ingraham

Since you already know about potentiometers, resolvers, and absolute encoders I'm not sure what you're asking. Call up some vendors you work with on a regular basis and have them bring at least two units to check out. See if when you orient the device and the shaft to the same position that you get the same reading. I would guess (but don't know for sure) that you're better off with a digital absolute encoder rather than a pot or resolver. There are dozens to choose from with all kinds of interfaces. The specifics don't matter much; your vendor relationships are going to be more important than the tech specs on a datasheet.

Good luck,
James Ingraham
Sage Automation, Inc.
The precise potentiometer with analog input in your controller is simpler option enough for asked accuracy. Unlike potentiometer both other position sensors as abs. encoder or resolver are need in digital encoding devices.

But you must be care about sensor-to-shaft attachment for compatibility between user's devices.