How do I use a quadrature encoder as an external clock (PCI 6229)

[Kejoglo]

Hello, ( a similar post has been placed on DAQ forum apologies as I did not know best place)

I have a PCI 6229 M Series data acquisition card. I want to use a quadrature encoder to be the external clock driving the acquisition of a number of signals. I have set up reading 24 signals each time a clock pulse is received using the DAQ assistant and set my external clock to pin pfi8 (I think) this is then connected to an encoder output. This works well enough until the encoder is run too fast when it appears I am either missing pulses or getting bounce.

How can I set up to clock using a quadrature encoder? I have seen a number of questions on this forum regarding quadrature encoders and reverse counting but not on using them as an external clock.

Basically I want to have the stability and "bounceless" nature of using two outputs from a quadrature encoder whilst still using an external clock. Is this just a case of configuring controls to certain pfi's? If so how is it done?

Any help or pointers would be helpful. So far I have managed very nicely by simply using the DAQ assistant and the interface it has would suggest that if configured for a certain pfi pin I could actually still use it.

Thanks in advance.

Kevin

[AdamB]

Hi,

Well I've had alook into this for you and I'm not quite sure I understand what you are looking for.

Is it possible for you to phone back in to support?

The reason you are seeing bounce at high speeds, or indeed loss of points, is due to the sampling rate that you have set up.

What you will find is that the trigger will start an aquisition of a number of points at a certain rate.  If your sampling rate is too low then you will not finish that sample batch before the next set of samples is recorded.

It is possible to use an external clock into a trigger or digital line, however this will limit the number of samples you can take to the speed of your encoder.

If you increase your sampling rates, and then configure a start trigger from a single input from the encoder you will be able to record a number of samples after a rising/falling edge.  (Set the clock as an internal clock)

Hope this helps

AdamB

[AdamB]

Here's a DAQ assistant set up to sample 500 samples on a digital input that triggers the sampling

Thanx

AdamB

NIUK

[AdamB]

Hi,

Here is a simple example that uses the PFIO8 input as the clock counter.

Hope this helps

AdamB

NIUK