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Member t29
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speed or velocity

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 ?

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Re: speed or velocity

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?

 

Preston Johnson
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Asset Monitoring Systems
Vibration Analyst II - www.vibinst.org
National Instruments
preston.johnson@ni.com
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
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Member t29
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Re: speed or velocity

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.

 

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Re: speed or velocity

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. 

 

 

Preston Johnson
Global Program Manager
Asset Monitoring Systems
Vibration Analyst II - www.vibinst.org
National Instruments
preston.johnson@ni.com
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
512-683-5444
Member t29
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t29
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Re: speed or velocity

NI 9234 is not supporting the analog signal 'frequency'. It supports only 'acceleration'.

how to proceed using this signal?

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Re: speed or velocity

select a voltage and then choose the 9234 as the device.  With a property node in LabVIEW you can turn on AC coupling
Preston Johnson
Global Program Manager
Asset Monitoring Systems
Vibration Analyst II - www.vibinst.org
National Instruments
preston.johnson@ni.com
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
512-683-5444
Member t29
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t29
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Re: speed or velocity

it doesn't support voltage also, only acceleration.

also can u please tell which device to use for flow measurement- NI 9403 or NI 9219? and what is the application of NI 9403?