9401 counting by quadrature encoder error

I use a 9401 module in a chassis 9188 to measure the position of a tree in 1E6 County/rev. The signal is an AQuadB emulated from an AKD Kollmorgen servo drive. My problem is that when the player is turned on, the noise it makes picked up as very positive figures by the 9401. The player has outputs RS485 but my cable length is short and well armored, so I thought it would work very well. It is wired like this:

9401 CTR1 channel

A +: 9401 pin 20

B +: 9401 pin 23

GND: 9401 commune

The cable shield: 9401 commune

Is this product because the encoder signal is differential, or is my bet to the ground/shield OK? If I disable the encoder entirely the 9401 picks up a zero solid. Should I use a kind of RS485 converter to TTL?

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In addition to the advice of John to help protect against digital noise, I also recommend that it would be a good idea to convert the differential asymmetric TTL formally.  I had opportunities in the past where I had an ambivalent connection channel differential encoder of 5V to a DAQ card and often, it would work properly.  But there have also been moments where differential signals (-) were trying to drift over the other while being tied to the digital earth common DAQ, causing sporadic but strange counting behaviors.  At least that's the diagnosis I'm come up with at the time.

These questions disappeared immediately and permanently after putting in a differential to the TTL converter.  Here is a link to the productI used (and then successfully reused on the following projects).  Just check the specifications of your particular differential signals compared to what this product is to spec'ed to manage.

-Kevin P

Tags: NI Hardware

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