PCI-6220 Counter problem

[Maziar.Ab]

Hi

I have a PCI-6220 (M series) with SCC-68 terminal. I wanna connect a quadrature encoder which have 3 channels with 6 wires; A A-, B B-, Z Z-, but in pinout figure there is no place for A-, B-, Z-. for connecting. In DAQmx in virtual channel task, the DAQ can't read negative pulse (In thick unit). What should i do ?? Please help me. Where should i connect A-, B-, Z-??

Thank you

[Kevin_Price]

Signals in +/- pairs usually indicates that they are a differential pair.   Your board needs single-ended signals.   You'll need to look into the electrical specs for your encoder to learn what it puts out and then find a way to convert to TTL.

It's been a lot of years since I bought such a device and the one I bought is no longer available for sale.  Look around, something will turn up.

Note: you *do* need to know the nature of the differential pair first.  I've seen some where the difference toggles between +5 and -5 (nominal voltages at 5 and 0), and I've see some where the difference toggles between +10 and -10 (nominal voltages at +5 and -5).

-Kevin P

[Maziar.Ab]

well noted.Thank you very much.

One more question. Can i read the negative pulse of encoder without the device?? Because i see the DAQ device reads negative number when i select unit to degree!! Does it show the motor angle in degree? because i tested it and the angle in degree is not right  !!

[Kevin_Price]

I can't predict how the board will handle your differential signals if you don't use a differential-to-TTL converter device.  Some edges may be recognized as edges, others may not.  This is actually a *worse* situation than if all edges failed to be recognized, because it can lull you into thinking everything's ok when it maybe really isn't.

Read positive values vs. negative values will depend on how it's wired, how it's configured, and what the actual motion direction is.  It's normal to be able to see both positive and negative changes.  The ability to detect direction is one of the main advantages of a 2-channel quadrature encoder over a 1-channel encoder.

Correct scaling to degrees depends on having correct config setting for "pulses per revolution" and "decoding type".  You might also be having trouble with partial success at recognizing edges on the differential signals, as mentioned earlier.

-Kevin P