buffered high speed capture

[varmih]

Hello,

I am looking for any example of an on-board buffered High Speed (HS) capture. The only example I've found so far (see http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3D77D56A4E034080020E74861&p_node=DZ52480&p_source=External) deals with single HS capture mode and cannot work with the high frequency capture of about 1000 Hz that I am interested in. Can anybody help me?

Thanks.

[Jochen]

Which type of motion control board are you using? The only board type that supports a HSC rate as you expect is the 7350 series. The 735x boards support HSC rates up to 2 kHz. With 734x boards there is no way to capture positions faster than 200 Hz as you have to reenable the HSC circuitry after each trigger occurrence.

For the 7350 a LabVIEW example installs with the NI-Motion driver called "Buffered High-Speed Capture.vi" that captures position values to an onboard buffer without the need of onboard programming.

Best regards,

Jochen Klier
National Instruments Germany

[varmih]

Thank you for the exact answer. Unfortunately I have 7344 board...

[Jochen]

In this case NI can offer you two solutions:

1. NI offers hardware upgrades. You could contact your local NI branch and ask them to exchange your 7344 with a 7354 (or a 7352 if you don't need more than two axes). This would be the best and easiest solution but maybe not the cheapest. At least you could ask them to send you a quote. Please take into account that the connector of the 7354 is compatible to the connector of the 7344 so you wouldn't have to buy additional cables or connector blocks.

2. You could add a PCI-6601 counter board to your setup. The 6601 can be used to measure positions by either connecting the encoder of your motor to the inputs of the 6601 (in parallel to the 7344) or if you don't use an encoder (open loop stepper) then you could measure the step/dir signal of the 7344 with the 6601. You can connect your trigger signal to the 6601 for a buffered position measurement. The 6601 supports DMA so a position measurement rate of 1 kHz is absolutely no problem.
The disadvantage of this solution is obviously the additional cabling and a higher complexity in programming.

Regards,

Jochenhttp://forums.ni.com/ni/board/post?board.id=240&message.reply_to_id=2110#
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[varmih]

I also use in my application PCI-6251 board having two counters. It seems to me that this board can be utilized for this purpose instead of 6601. The problem is that I have to acquire simultaneously some sensor voltage and the encoder position and I do not know:

1. How to synchronize sample clock of analog input and counter action of my 6251 board;
2. How to deal with phase A and phase B of motor encoder in order to get the motor position.

I would be very grateful if you could advise me on how the above two questions can be solved.

Thank you.

[Jochen]

1. There are several ways to do this. One way would be to use the sample clock as external clock for a buffered position measurement.
2. M-Series devices provide direct connectivity for quadrature encoder signals (Ctr0: A=PFI8, B=PFI10; Ctr1:A=PFI3, B=PFI11).

There is a ready to run LabVIEW example that should answer both of your questions: Meas Angular Position-Buffered-Cont-Ext Clk.vi (ships with LabVIEW).

Regards,

Jochen

[varmih]

Thank you very much, Jochen. At last it works!