How to verify the correction of the optical encoder on motor?

I am now designing a DC motor with a optical encoder assembling at the end of the motor. After I have checked with the specification of the encoder, there are no problems for me to understand how it function and how it works.

Now, I would like to assembly the transmissive encoder onto the end of the motor. Then I have some problems happened:

- For 1 turn motor rotation, encoder will give out 500 signal (because of 500CPR), I don't know how to verify the signal correct or not. I am using a 2 channel encoder and hence the 2 signal will be 90 degree phase shift. However, I really don't know how to use CRO to measure a contiunous high frequency signal.

- If the assembly between encoder and motor has some problems (aliasment, eccentricty, perpendicularity, etc...) I would like to know that can I check the encoder signal to verify the regarding problems happened in my motor assembly?

- I just have a CRO, no other special equipments. And I would like to know which extra equipment is needed for me to test the encoder.

Thanks~

Reply to
Electronic Swear
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If you were to put the two signals into a mixer, (after suitable limiting and buffering), you would be able to observe cyclic variations in how well the inputs conform to quadrature phasing. You would filter out the mixer output's 2 * f component and observe what was left. It would be simple to use a low pass filter after each mixer input to see what the duty cycle variation looked like.

A frequency counter might be useful, but I would use the above phase error observation and place limits on what was allowed in production to ensure adequate margin in the recovered position/speed.

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--Larry Brasfield
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Reply to
Larry Brasfield

Not with a CRO. Output the encoder into whatever counter you are using. Rig up some hard fiducial locator- say a screw you can screw into a pockmark on the shaft, puulley or whatever. Zero with it screwed in, rotate the motor, screw in again, and the reading should be a multiple of the encoder count (probably 500x4xn rotations - a 500 line encoder usually means 2000 counts/rev). Rotate back to the start, screw in, should be zero. How near to exact depends on how good your fiducial mark is.

I don't know how you'll get aliasing- or rather, if the frequency response of your motor/ encoder assembly is higher than about a fifth of the bandidth of your control circuitry, redesign the whole system.

Eccentricity, etc. will give you cyclical errors, in other words the 'degree' measured by your encoder will vary as you rotate it. You'll need some means of knowing what the actual angle is to calibrate this out.

Paul Burke

Reply to
Paul Burke

hahahahaaaaaaaaaaaaaaaaaaaa! ONE FAKE TROLL TAKEN IN BY ANOTHER- TOO GODDAMMED FUNNY!!!!!!!!!!!!

Reply to
Fred Bloggs

I would like to know that is there any equipments can count the input signal and capture out 2 channel waveform for compare~

For TekXXXonix, there are some equipments call Logic anaylizer. And I want to know that the regarding equipment is suitable for checking encoder signal or for verifying the assemblied motor with encoder.

------------------------------------------------ If you were to put the two signals into a mixer, (after suitable limiting and buffering), you would be able to observe cyclic variations in how well the inputs conform to quadrature phasing. You would filter out the mixer output's 2 * f component and observe what was left. It would be simple to use a low pass filter after each mixer input to see what the duty cycle variation looked like.

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For the quoted procedures, I am sorry I cannot understand. The mixer is a equipment or using a self-made circuit to do so? Would you please describle more detail or in a simple way.

Thanks~

Reply to
Electronic Swear

On 23 Mar 2005 23:39:27 -0800, swear snipped-for-privacy@hotmail.com (Electronic Swear) wroth:

Save one motor/encoder for use as a "standard". Make sure that it works well in the system.

When you want to test and/or adjust another motor, connect the shaft of the test motor to the standard motor with a rigid coupling. Power up the standard motor and run it at some convenient speed.

Use a two channel oscilloscope to view each of the encoder signal phases on the test and standard motors. Any deviation will be readily visible. Make your adjustments to the test motor to minimize the deviations.

Jim

Reply to
James Meyer

Thank you for your suggestion.

May I know that can I use some equipment to measure the output signal? For example: logic analysier, frequency counter?

If there are some all-in-one solutions, it will be better to purchase for measurement.

Reply to
Electronic Swear

On 30 Mar 2005 17:58:05 -0800, swear snipped-for-privacy@hotmail.com (Electronic Swear) wroth:

The best instrument I can think of would be a digital oscilloscope with at least two channels, a sampling speed compatable with the motor's speed, and the ability to store the input waveforms for later analysis.

Such an oscilloscope would be a valuable general purpose test instrument for many different uses. It would function as a logic analyzer as well as a frequency counter. You may find that additional instruments would make the measurements easier, but a good oscilloscope should be your first investment.

Jim

Reply to
James Meyer

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