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Looking for Non-Con. RPM Sensor for use with Lab View

Hey all,
 
I'm not as experienced with any of this as I'm sure some of you are, so I'm hoping that someone can assist.
 
I'm trying to measure the speed of an impeller for a class. We want to use the LabView software to record the data, so that possibly we can record different things at the same time.
 
The impeller is plastic, and I was looking for a non-contact method of measuring the RPM's of the Impeller. I have already found many optical sensors that will measure the RPM easily, but none of which I could find as a stand-alone product that I could have the output into lab view.
 
Any help would be greatly appreciated.
 
Thank You.
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Message 1 of 13
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A through-beam optical proximity sensor with a TTL output (0-5V) would interface nicely to a DAQ card with a counter/timer on board so it can measure frequency.
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Message 2 of 13
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Thank You, I'll be on the search for something then.

If anyone has any specific sensors they know of that would be useful, please let me know, otherwise I will post my findings when I come accross them 🙂
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Message 3 of 13
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The measurement of rpm ( whether using LV or otherwise ) can be done in  few basic  fashions : Mount a  gear disc, encoder or  some such method on the shaft  to interrupt a light source / magnetic sensor and log in the resulting digital pulses as frequency and display after conversion as rpm.  Or get the pulses , convert them into an analog voltage with an F-V convertor chip like the LM2917 and display the analog voltage as rpm. Or use a tacho generator  and directly scale the output voltage as rpm ( the easiest of all ).

Each method has its pros and cons and which to use will depend on the range of rpm that you want to display and with what accuracy you want to display.

Get back with the information and we can suggest methods.

Raghunathan
Raghunathan
LabVIEW to Automate Hydraulic Test rigs.
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Message 4 of 13
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Optical will be the simplest to set up, and will have lowest influence on the measurand (the fan speed in this instance).

You could either place a peice of retro-reflective tape on the blade and measure from one side or use the blade to break the beam.

The tape allows you to increase the received light from the blade / shaft surface by increasing the reflectivity, you only get one pulse for each piece of reflective tape so normally one pulse per revolution (rev). If you use the blade to break the beam you get a pulse for each blade, which will be a higher frequency than one pulse per rev, this then has to be processed to arrive at the shaft RPM.

You can use an infra red diode as found in typical remote controllers for T.Vs or a visible LED. An old ball style mouse also has suitable sensors inside if you are strapped for cash. The infra red sensor will be less sensitive to ambient light variation if you select the appropriate sensor. These devices are available from most electronics suppliers, watch the wavelength specification to determine if the sensor is suitable for the light source, if the fan is rotating at high speed (thousands of RPM) watch the maximum switching frequency available from the receiver device.

For very low speeds or very high speeds make sure you have sufficient counts available if you are using a counter to time events. In either case you may need to ensure that any conditioning circuitry switches reliably at the anicipated operating frequencys, you could test the conditioning circuits with a signal generator or just hope they will switch cleanly.

Essentially the conditioning circuit (or the receiver) can be done using a single transistor say a BC109C or other transistor device with a couple of biasing resistors. A general pupose op-amp will also suffice if correctly connected. Test it BEFORE connecting it to your expensive computer and data aquisition hardware. You will find plenty of circuits on the net for this kind of stuff, a search on google will yield a few hundred.

Message Edité par Conseils le 11-20-2005 10:19 PM

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Message 5 of 13
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Thank you for the information, I do want to get the pulses and convert them into an analog voltage, This is the method I am shooting for. What sensor would be best for this?

 

Thank You again.

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Message 6 of 13
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Try Banner electronics, D12sn6fpy  0-180,000 RPM 0-10v analog output, very clean i have been using them for years.
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Message 7 of 13
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Hi!

Thanks for the response, do you happen to have a contact or web link for this?

Thanks again for all the help everyone.
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Message 8 of 13
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What are your resons for implementing an analogue interface?

I can think of any number of reasons but I am interested in your thoughts.

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Message 9 of 13
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Hi,

I am looking for the best way to leave open the option of recording multiple measurements at the same time, one being this one, and being able to compare them over time with some precision.


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Message 10 of 13
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