Looking for an encoder to go with a Micrologix 1400. The encoder shaft will be turned by a shaft at 60 RPM and I need to know the shaft's location within .3 degrees. Does it matter what type of output the encoder has? Anyone have any brand recommendations (using a flange mount encoder)

Thanks

I've had good luck with BEI.

With 0.3 degrees, you're looking at 1200 ppr or more. If you want to know that number within +/-50%, then it doubles to 2400 ppr. The next higher "standard" (binary) size is 4096 ppr. Since you said shaft location but didn't specify if you can accept a "zero" function, then you'll need a 12 bit absolute encoder. If you can somehow zero/clear things or you can somehow introduce a timing mark then you could drop this to a quadrature encoder instead.

Either way at 60 RPM X 4096 PPR, you're looking at an input speed of 60 RPM / 60 secs/min = 1 rev/second, or 4096 pulses per second. At this relatively "slow" speed of only around 4 kHz, noise won't be a serious factor and you can probably get away with an open collector (push/pull) type non-differential input. However if you are even vaguely concerned about noise/interference, always go for the differential line driver. It is slightly more complicated to wire up but will reward you in the long run.

More important than the mechanical connection, consider the coupling you will be using, and also consider the physical connector. A lot of encoders use military style connectors, which are a real pain to put together. There aren't many out there but you can find a few with M12 type connectors and after going through the trouble of adopting military style connectors on a project last year, I'd use the M12 connectors even if it is a little harder to find the encoders and the cables.

As for brands, I had good luck with BEI. Allen Bradley encoders are actually rebranded Danaher (Dynapar)'s, which are also a good brand. I also had good luck with the units from Simpson Electric, but the resolution is way below what you need.

I didn't check the 1400 specs but 360deg/0.3deg=1200 so 1200 PPR or better is needed for 1x decoding.
if you can use 4x, 300PPR or better will do just as well. brick PLCs in general have low specs on high speed counting / pulse trains (5-100kHz or so, depends on model).
keep that in mind before selecting encoder because too high PPR will also do no good, you don't want to counter to miss the pulse (although with 60RPM this is not very likely)

BEI. They just work. Had a contractor doing a job drop the pullup resistors (on the unit's open collector outputs) by two thirds and the encoder continued to work. It didn't like it though. The overheating caused an intermittent tracking problem but, once the resistance was restored to spec., no more trouble.

Thanks All
I have selected a Red Lion Encoder with an open collector output.

Everything makes sense, but how do I calculate the size of the pullup resistor I need?

you need to see what works for particular PLC input and what encoder can tolerate. idea is to produce sufficient swings that will be recognised as ON/OFF transitions. something in order 1.5-2.2k is good starting value (thst is about 1/2 of the typical PLC input impedance which would produce signal in range 0 to 2/3 of supply voltage). the lower the resistor value, the better signal for the PLC, but the current on encoder is greater. check voltage rating of the encoder output because if it is only 7 or 12V, you don't want to pull it high to 24V (for that it should be rated 30V or more).

Thanks - the 1.5 K resistors did the trick