How do you count the frequency of a boolean signal?

Hi, I'm new to LabVIEW, so I suspect this is propbably quite a simple problem.
I'm developing an optical tacometer for a model gas turbine engine. I have a boolean signal in labview which is switching at a frequency between 4 and 26Hz. I need a live readout of the frequency of this signal.
Does anyone know how I could do this? Any help would be really appreciated!
Many thanks
Will
Solved!
Go to Solution.

This vi should work for you
Tim
Johnson Controls
Holland Michigan
Attachments:
Calculate Frequency from boolean.vi ‏11 KB

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How do you count the frequency of a booloen signal?

Hi, I'm new to LabVIEW, so I suspect this is propbably quite a simple problem.
I'm developing an optical tacometer for a model gas turbine engine. I have a boolean signal in labview switching between 4 and 26Hz. I need a live readout of the frequency of this signal.
Does anyone know how I could do this? Any help would be really appreciated!
Many thanks
Will

New post here...
http://forums.ni.com/ni/board/message?board.id=170&message.id=481337
Rich R
Applications Engineer
National Instruments UK & Ireland

How do you count the multiple columns of a field in a table

How do you count the multiple columns of a field in a table

Hi,
4396bf34-e890-4202-a6b0-4e08c9ff0e89 wrote:
How do you count the multiple columns of a field in a table
Whenever you have a problem, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all tables involved, and also post the results you want from that data.
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How do you find the frequency of a small sample size and a square wave.

I am collecting data from ten 12v pulses that are seperated pretty uniformly. The pulses make a square wave. I need to know how to input this small sample size and find it frequency. I need this frequency to be output in a readable file. Im not very knowledgeable in labview so if you try and help me please be very descriptive.
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Sorry about duplicate post. My internet connection is very slow today.
Message Edited by johnsold on 05-31-2010 12:05 PM

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How can I measure the frequency of an analog signal?

Hi, I am trying to measure the frequency of VAC signal coming from a gas turbine engine at my university. If I can get the values of frequency, I can determine the speed (RPM) of the engine. I am fairly new to LabVIEW and I have been looking through manuals like crazy in order to find out how to obtain the frequency. I have measured the signal with an oscilliscope and the highest frequecy will be about 1.5kHz. I am currently using a USB-6218 and it can collect the voltage signal with ease, but it won't give be analog frequency so simply. Can anyone explain a way for me to obtain the frequency values? And if you could show or tell me in a very simple way (because I am not very fluent in LabVIEW yet), that would be amazing! Thanks!

Check this out:
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RPM.vi ‏17 KB

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Thanks for the responses. That was fast.
I was hoping to fit it all in one cell, but I guess I could hide the columns used for calculation. I tried Badunit's Function and it works. However I found that if I have a column of all the same number it will return 0, when in fact it should return 1. Like if I had a column of 14s I should get one, because the number of different values that appears is 1. Also a minor note is that COUNTIF(B$2:B2,B2) should be COUNTIF(B2:B$2,B2), that makes sure that if you have anything below it doesn't interfere. At least that's what made it work for me.
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How do you count the frequency of a boolean signal?

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