My place of work has recently acquired a Hydraulic Press Break from the 80's. It has a CNC controlled back stop which is driven by a DC motor and Screw drive. The encoder which couples to the motor provides feedback for the control loop.

I have determined the Encoder is faulty as when i rotate it clockwise by one turn it increments by 5mm but when I rotate it anti-clockwise by 1 turn it increments by 10mm (approximately). It also feels quite clunky when i rotate it.

I would like to replace the encoder however I am not sure how to go about choosing an encoder.

What do pins B and C on the pin diagram represent? What do the numbers on the encoder represent? Would this encoder have a zero pulse?

Encoder reads 32/500N05.47

The top pin diagram show the outputs of the encoder

  • 1
    $\begingroup$ it may be this ... en.m.wikipedia.org/wiki/Incremental_encoder#Quadrature_outputs $\endgroup$
    – jsotola
    Commented Jun 23, 2020 at 22:31
  • $\begingroup$ This is helpful! The nature of an incremental encoder makes me think there would be no zero pulse as the external controller would be storing and incrementing the count. $\endgroup$ Commented Jun 24, 2020 at 0:31
  • $\begingroup$ Haha thanks - edits made. There doesn't appear to be a home sensor. Things I've read in the operators Manual such as "perform regular backstop calibration" and "try to turn off the controller as little as possible". Makes me think they don't rely on any home sensors or such things. $\endgroup$ Commented Jun 24, 2020 at 0:51

1 Answer 1


First, you need to find out how the encoder is used in your system. There are two sketches of plugs, I assume your encoder is connected as shown in the upper sketch.

Since the company who produced this is still producing and selling encoders, website here, I would start by giving them a call.

  • First of all ask, if they can provide a drop in replacement. It is a long shot, but not that uncommon in the automation/CNC world.
  • You can ask the manufacturer for a technical specification for the encoder. How many counts/revolution does the encoder output is the main important characteristic to choose a replacement. Voltage of the output signals is probably 5 V but it does not hurt to ask to make sure. It is unclear what "H-I = Motor" means.
  • The technical spec can help you shop around from other vendors. You can all sales people of different companies and ask them if they have something compatible to your spec sheet.
  • $\begingroup$ Thank you, ill call them and see if they can help. I've tried to track down other parts of this machine and am always met with "we have no information on this machine or these parts - its nearly a 40 year old machine". If I can just determine what the numbers on the encoder mean it should be a big help towards finding another encoder $\endgroup$ Commented Jun 24, 2020 at 20:23
  • $\begingroup$ If it is broken, you can disassemble it and count the ticks per revolution yourself. That is the main important characteristic, besides voltage. $\endgroup$
    – 50k4
    Commented Jun 25, 2020 at 8:42

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