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harmonics in quadrature encoder

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raman00084

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i am using a yaskwa servo motor to move a linear table. from the drive i am reciving the qei pulses ( a+ a- b+ b- c+ c-) through line driver am26ls32 using 330 ohms as teminating resistor. every thing is working fine if i connect to oscilloscope i am getting quadrature pulses but the pulses are not exactly square it contains harmonics ( noise) how to reduce the harmonics i am using only shielded wire
it is common to get harmonics in qei? if i connect to pic micro controller in built qei peripheral i am getting the value currectly with +/- 1 are 2 pulses error.

kindly help me how to reduce the harmonics in qei . i want exact square are rectangle wave form.

regards
kalyan
 

SunnySkyguy

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Inductive loads with capacitive cable will always resonate. Poor test methods with long ground leads add to the observation, so remove clip and gnd.to probe using pin and barrel.

Ringing is a result of high Q , low Rs and return loss .

You can add ferrite beads or CM choke for reduction in EMI and use low capacitance cable like twisted pair 6 turns per foot but depends on gap and dielectric constant of insulation.
 

raman00084

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Inductive loads with capacitive cable will always resonate. Poor test methods with long ground leads add to the observation, so remove clip and gnd.to probe using pin and barrel.

Ringing is a result of high Q , low Rs and return loss .

You can add ferrite beads or CM choke for reduction in EMI and use low capacitance cable like twisted pair 6 turns per foot but depends on gap and dielectric constant of insulation.

i am using cat 5 lan cable that is twisted pair with shelding. i cannot understand the test methord you said can you explain in detail.
 

SunnySkyguy

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Remove scope tip and ground wire. Now probe is just tip and ring. Choose shortest connections to source or load to measure result.

Or use 2 probes , calibrated and balanced and use A-B mode.
 

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