新人求助如何测量How to measure contact bounce？

[wanglei83113]

本人接触Labview不久， 很不熟悉， 但现在急需知道如何测量Contact bounce的时间长度。 如图所示， 忘达人指点。

I am new to Labview and urgently need to know how to measure the contact bounce period. Hope experts would help or give me some tips. Many thanks.

Usually the period is less than 2 mS.

Message Edited by wanglei83113 on 02-02-2009 08:05 AM

Message Edited by wanglei83113 on 02-02-2009 08:13 AM

[smercurio_fc]

What kind of hardware do you have? Are you using a DAQ card, or some other instrument, like a scope or a logc analyzer? If you're using a DAQ, then you need to do some DAQ acquisition. Do you know how to do this? If not, you will need to spend some time going over the DAQ tutorials and the examples that ship with LabVIEW (there's lots of them). You can also start at the Measurement Fundamentals page.

Once you do that there's lots of built-in functions for analyzing the signal, but a lot of it depends on how clean your signal is. What you've shown is an ideal signal. You will not have this. Thus, you may have some offset, or noise on the line which may or may not affect your analysis. 

[wanglei83113]

Thank you my friend, I am using DAQ cards, but I also have DMM card.

My objective is to measure the contact bounce period for multiple DUTs, and it is best to measure them at the same time.

It's rubber mat switch. Not sure of the waveform yet, but I will take some measurement soon using a scope.

[KateB]

Hi Wanglei,



I don't think there's a shortcut to measure this.

I beleive you've to play around with data array manually.

Let's assume that the acquired data is for rising edge.

Then, you should run an array to find the first data index that is higher that Vil, index0.

After that, reverse an array, and run through it to find the first index that is lower than Vih, index1.

The resulted period is (array size - index1 - index0 + 1)/sampling rate.

For falling edge, the algorithm should be pretty much the same, but other way around.



Regards, Kate

[smercurio_fc · Accepted solution]

There are built-in VIs that will provide you falling/rising measurements as well as pulse measurements. You can use, for instance, the Transition Measurements VI to find the rising/falling edges and from this calculate the pulse widths. This can be used to find out where the large pulse is, and from that calculate the bounce time before and after. Attached is an example (LV 8.2) of using these functions to calculate the pulse widths using the simulated, ideal signal that you had shown.