optical encoder and analog sampling

[sunny****]

Hello, I'm currently using Labview to sample metrics on an internal combustion engine. Pretty much, we currently have an optical encoder and two analog inputs. The way the program is currently setup, I believe the analog inputs samples are triggered by the optical encoder. The difficulty that i have been running in to, is that i would like to sample the encoder angles at a higher sampling frequency and at the same time add in a couple extra analog inputs. I'm using a PCI-6220 so it has a 250kS/s cap. I was wondering if instead of triggering the sample that i set up a sampling method for the encoder and the analog channels separately. Would the data multiplex cleanly. Or would their be some sort of delay between the analog and digital sampling. Thanks

Sunny

[Conseils]

Assuming that the encoder is something like a 128 pulses per rev type then I would imagine that the ecoder is connected to the timer counter input, this would be the best way to measure the angular position. Under these conditions the anlogue sampling rate would be independant of the angular position measurement. The angular position resolution would be limited by the clock speed on the data aquisition card.

It's possible that the encoder is providing a one pulse per rev synchronisation which is configured for TDC, in which case you can set up the encoder to start the aquisition from a digital trigger. Again the analogue sampling rate is seperate to the trigger mechanisim. There will be some form of delay between the trigger and the start of aquisition but I believe you will find it is very small when compared to the sampling rate of the analogue sampling.

I think that you should check the detail of the connections as it will have a large impact on how you manage the measurement.

What metrics are you measuring and what are you trying to relate them to? What kind of engine is it?

Message Edité par Conseils le 02-05-2006 12:42 PM

Message Edité par Conseils le 02-05-2006 12:42 PM