Multifunction DAQ
Reading Absolute SSI Encoder with X Series USB-6363
Hello,
I am troubling with an encoder that uses SSI interface,,, As the subject says i am trying to read encoder with an X Series USB 6363 DAQ,,, And Encoder has a 13bit resolution, according the manual, it needs 14 pulse for a complete data transfer,, data transfer frequency depending on clock frequency and it can be 50 Khz to 2 Mhz,,, and between 14 pulse there is a delay,,monoflop time 15us,,, Encoder uses Clock(+) and Clock(-) for timing and Data(+) and Data(-) for data transfer,, Firstly how can i generate and read differential digital signals with my configuration if its possible... and if itsnt possible it will work if i wire (-) lines to GND??
Anyway what i have done with no success, i configured CO with Daq Assistant for N Pulses with 14 Samples to Write and Timing type Implicit and Initial delay 17us, Idle State High (Encoder requires idle high) and High and Low time for 500n ... and Wire Clock(+) to CO and Clock(-) to D GND,,, for acuiring signal i tried both AI and DI and both no success ( i wired Data(+) to AI 0+ and Data(-) to AI 0- for differential Analog measurement to see anything but no success and Data(+) to P0.0 and Data(-) to D GND for Digital measurement but again no success)
There are some topics about SSI encoder but i dont find any solution for my case,, so anyone can help?
T=Depending on SSI Clock Rate (for my case 1us)
t1=T/2
n=13bit for my case
t3=Monoflop Time(15us)
t2=Data refresh rate (1us)
Manual for Encoder : Operating Manual
Datasheet for Encoder : Encoder Datasheet
From the encoder manual your connections should look something like this:
The output of the DAQ card does not match the diagram of course. To fix this, I would suggest adding your own buffer circuit:
1. You must convert the single-ended TTL signal from the DAQ card into the differential signal for the encoder clock (I don't believe connecting Clock - to DGND will work).
2. The digital outputs of the DAQ device are limited to 16 mA or 24 mA depending on which lines and whether the line is an output or an input. In the best case scenario, 24 mA across 120 Ohms is only 2.88 Volts.
Kubler might be able to give a more specific recommendation for something that they know will work with their encoders.
On the input side, you would need to add the 120 Ohm resistor yourself. I would start with an analog input to confirm the output voltages, and from there you might consider switching to digital to make the programming easier (I'd suggest a buffer here as well if you use digital inputs but it might not be necessary depending on the voltages).
Best Regards,
@John_P1 wrote:
From the encoder manual your connections should look something like this:
The output of the DAQ card does not match the diagram of course. To fix this, I would suggest adding your own buffer circuit:
1. You must convert the single-ended TTL signal from the DAQ card into the differential signal for the encoder clock (I don't believe connecting Clock - to DGND will work).
2. The digital outputs of the DAQ device are limited to 16 mA or 24 mA depending on which lines and whether the line is an output or an input. In the best case scenario, 24 mA across 120 Ohms is only 2.88 Volts.
Kubler might be able to give a more specific recommendation for something that they know will work with their encoders.
On the input side, you would need to add the 120 Ohm resistor yourself. I would start with an analog input to confirm the output voltages, and from there you might consider switching to digital to make the programming easier (I'd suggest a buffer here as well if you use digital inputs but it might not be necessary depending on the voltages).
Best Regards,
Thank you for your post, John ,,
So this means i wont be able to read that sensor with my USB-6363 :(,, i did contact with Kubler in Tr,, and they send me a sample encoder to see if i can read it with my DAQ or not,,, they cant be that helpful with NI products :S
Anyway i have some confuses with the Timing.vi,,, when i try to route Ctr0InternalOutput, i cant see that terminal in the I/O connector... it was weird :S i actually route with wiring... X series should have routes internally, shouldnt it?
NI has some differential digital signals I/O products,,, should i get a one of them to overcome that resistor problem?
@vbakircioglu wrote:
Anyway i have some confuses with the Timing.vi,,, when i try to route Ctr0InternalOutput, i cant see that terminal in the I/O connector... it was weird
i actually route with wiring... X series should have routes internally, shouldnt it?
It does have internal routes, but they are hidden by default. See here.
@vbakircioglu wrote:
NI has some differential digital signals I/O products,,, should i get a one of them to overcome that resistor problem?
I don't really think this is a "problem", it's just a requirement for how you have to interface with this particular encoder. I'm not sure you'll find the exact product you are looking for with 120 Ohm impedance inputs and differential digital outputs with appropriate voltage and timing specs. So you'll need to use some sort of conditioning anyway. Are external components absolutely not an option?
If changing hardware is an option, you might instead consider changing the encoder to something that outputs an A and B signal at TTL logic levels which would be much easier to interface with using the DAQ card.
Best Regards,
@John_P1 wrote:
@vbakircioglu wrote:Anyway i have some confuses with the Timing.vi,,, when i try to route Ctr0InternalOutput, i cant see that terminal in the I/O connector... it was weird
It does have internal routes, but they are hidden by default. See here.
@vbakircioglu wrote:NI has some differential digital signals I/O products,,, should i get a one of them to overcome that resistor problem?
I don't really think this is a "problem", it's just a requirement for how you have to interface with this particular encoder. I'm not sure you'll find the exact product you are looking for with 120 Ohm impedance inputs and differential digital outputs with appropriate voltage and timing specs. So you'll need to use some sort of conditioning anyway. Are external components absolutely not an option?
If changing hardware is an option, you might instead consider changing the encoder to something that outputs an A and B signal at TTL logic levels which would be much easier to interface with using the DAQ card.
Best Regards,
Hello John, than you for your fast respond,,,
Nice post about I/O Terminal,,, you are absolutely right,,, i spent half a day for looking that terminal option :S and gave up at the end 🙂
Well, i can use external components but i dont know how to do 🙂 Actually i did put a 120 Ohm on Data line but i dont know how to get differential signals from TTL signals... i know Encoders with A and B signals are much more easy to read but i need an absolute encoder,,, and i dont know if there is an absolute encoder with that option..
