Measure Rotation of Bicycle

[ASIAN INSTITUE]

Hi all,

I want to measure bicycle speed by using Photomicrosensor connected with Labview via SCB-68. Please help me to make the Labview Program .


Thank you very much.

Thuong

[Dennis_Knutson]

You can't measure anything with the SCB-68. It's just a terminal block. You would need to connect the terminal block to a DAQ board. Do you have one? What make and model? What is the signal output of the sensor?

[ASIAN INSTITUE]

Yeah,, I connected the sensor to DAQ via SCB-68. The Output of that sensor is voltage as a pulse waveform. In order to measure speed , I need to know the frequency of that pulse wave. For more detail , Please see the attached file , in the page 3 it shows the output of the photo sensor that i am using .

Thank you for your help.

thuong

[Dennis_Knutson]

You still didn't provide the make and model of the DAQ board All you have to do is look at what's installed in the pc. You can also open MAX (Measurement & Automation Explorer) and it will be listed.

Let's assume that you have a fairly decent DAQ board from NI, that the board has a built-in frequency counter, and that you are using DAQmx. Open the Example finder and expand Hardware Input and Output>DAQmx>Counter Measurements>Digital Frequency. You can also just drop a DAQ Assistant on the block diagram, select Counter Input>Frequency.

If you don't have a counter on your board, then you can do an analog waveform capture and then use the Extract Single Tone function or the Tone Measurements Express VI.

When you find out the type of DAQ board, you can search http://www.ni.com/support/ for the model and find the manual. That will tell you what is and what isn't on the actual DAQ board.

[xseadog]

Hey

Pay Attention, when an esteemed knight of the realm asks you which DAQ card you are using then provide an answer

You should be able, by accessing your computer hardware properties  find out what DAQ card you have installed

Chow

xseadog

[ASIAN INSTITUE]

Yeah,, The DAQ board is PCI 6259, it supports counter and timer. Due to in PCI-6259 , It has ctr0& ctr1 , thus How can i connect the sensor wires properly that suitable to the channels.

Thank you.

[ASIAN INSTITUE]

Hi all,

I used the Extract Single Tone function or the Tone Measurements Express VI to measure frequency of the voltage waveform. However, due to of noise, when bicycle stop rotating, the frequency still has value. Therefore, the frequency measured will not be true or interfered by noise ( See the attached file )

Please help me to solve the problem

Thank you

[ASIAN INSTITUE]

The Labview file that I wrote,, The frequency is interfered by Noise. The frequency changes even when stop rotating.

Please hepl me

Thanks

[Dennis_Knutson]

You could compare the mean of the acquired to signal to some threshold and put the Extract single Tone inside a case statement.

[johnsold]

It is quite difficult to measure frequency = zero. What is the period of a zero-frequency signal? Infinity. Can you wait that long?

On the practical side you must decide what frequency is low enough that you can consider it to be zero. This may be determined by the usage of the data or by the time you are willing to wait for an update of the speed. For example if you need new data once per second, you cannot easily measure frequencies below 1 Hz.

One reason your data may continue changing after the wheel stops is due to the delay in the filters. When the wheel starts the indicated speeds do not immediately change to the new values. One of your filters has a 50 ms delay.

Lynn