# Help me to determine absolute encoder parameters

I see this encoder on the internet (SRM50-HFA0.)

I need to know:

1. What is the difference between "sine/cosine periods per revolution" and "number of the absolute ascertainable revolutions?"
2. What are the "total number of steps"/"integral non-linearity" and "differential non-linearity?"
3. Are the "REFSIN" and "REFCOS" signals -SIN and -COS signals?

• Please add the essential details from the datasheet (including the brand and part number) so we don't have to follow a link to know what it is and the question will make sense if the link dies. Oct 12, 2020 at 18:24
• Thank you, I have uploaded pictures of the datasheet as well. Oct 12, 2020 at 18:27
• I've used some of Sick's programmable incremental encoders (handy, as it can act as a spare for many different types) but I haven't seen this one. It looks like they're able to give out 1024 sine/cosine cycles for one revolution! Meanwhile they're tracking the revolutions and able to count up to 4096. Good question. There are a couple of Sick videos on YouTube but I can't find this model but some have extensive gear chains in the back. Oct 12, 2020 at 18:54
• read about hiperface , first: cdn.sick.com/media/docs/5/65/865/… Oct 12, 2020 at 18:57

sin/cos periods per revolution, means you get an output signal like depicted X 1024 times = 1 revolution of encoder, or vice versa the depicted signal trace equals to 1/1024-th rev's movement.

If you transform sin/cos signals into quadrature pulses, you then get 1024 pulses per revolution.

total number of steps, 4096 revolutions X 1024 sin/cos periods per revolution X 32 possibly the extrapolated positions within one sin/cos period, this number depends on ADC and used MCU/DSP.

EDIT:

total number of steps, 4096 revolutions X 32768 steps/turn

Are the "REFSIN" and "REFCOS" signals -SIN and -Cos signals?

Yes. See the Hiperface documentation.

What is the difference between "sine/cosine periods per revolution" and "number of the absolute ascertainable revolutions?"

sin/cos periods determine the position within one revolution, meanwhile there is yet another type of encoder embedded for multi turn. Usually a gearbox with a coded disk and hall sensors that do measure number of revolutions, similar like water meter.

Picture taken here

Some encoders use just a built in battery to store the absolute position, without a coded disk - in your case that would make sense