03-20-2010 11:14 AM
Iam working on a data aquisition project. so i have to measure speed of an internal combustion engine. Can any one please tell me which daq device to use from these - ni 9219, ni 9234, ni 9403 ?
03-20-2010 01:27 PM
it depends on the sensor you have available. Is it a keyphasor from the shaft, an output from the control system, or some other sensor?
03-21-2010 12:39 PM
hey thanks for replying.
we are using a proximity sensor for the speed measurement. it is connected to the crankshaft of the engine.
when we use ni 9219 and ni 9403, the message comes that-" no supported device found".this was for the analog signal as acceleration( we used this signal as there was no option for velocity or speed).
when we used ni9234, it supported the signal,but we got weird readings.
03-21-2010 02:42 PM
So for the proximity probe, you might notice (if you check with an oscope) that the proximity probe will have negative DC offset with an AC component on the signal. If you use the 9234 (you will need a high speed analog input) with AC coupling turned on, you can remove the DC offset and get the pulsing sequence from the proximity probe.
Then by doing a frequency estimate you have speed in Hz, multiply by 60 and you have RPM.
so try the 9234 with AC coupling.
03-26-2010 06:00 PM