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Topic Title: Using an oscilloscope to measure time
Topic Summary: Using an oscilloscope to measure the delay between two wires breaking
Created On: 02 September 2013 01:56 PM
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 02 September 2013 01:56 PM
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ryannorrington

Posts: 4
Joined: 29 July 2013

Is it possible to attach two circuits to an oscilloscope, where as the first circuit breaks, a timer starts and as the second one breaks the same timer stops. Effectively measuring the delay between the wires breaking? Thanks
 02 September 2013 03:00 PM
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kengreen

Posts: 400
Joined: 15 April 2013

dear Ryan,

I would not pretend to be an expert in this field but it would surely be a complicated setup if you're just trying to determine the breaking point of the wires. I would suggest that you pass a small current through each wire so that when a wire ruptures the current is interrupted. You should make these low-power currents to prevent arcing messing about with your breakpoints. There are a number of ways you can take it further perhaps easiest being digital logic components which are cheap and plentiful; it sounds to me like an ideal case for judicial application of AND or OR gates?

Ken Green
 02 September 2013 03:08 PM
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oneye

Posts: 158
Joined: 25 February 2008

It's a very long time since University days ...
but even then there were digital counter / timers that would time between events as described or measure accuratley pulse width.

An oscilloscope would not give a high resolution whereas a counter timer would give something like 0.002 s resolution.
 02 September 2013 03:58 PM
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kengreen

Posts: 400
Joined: 15 April 2013

very true oneeye on would not a digital counter timer be somewhat more expensive than a couple of digital chips? Apart from that build such a setup can be much more educational and satisfactory. Timing pulses are not difficult to generate; a crystal-controlled oscillator output applied to a square wave generator and differentiated - result a lovely stream of pulses which can be injected into an oscilloscope to measure almost any time interval depending on the resolution of the oscilloscope.

Ken Green
 02 September 2013 04:04 PM
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ANFierman

Posts: 136
Joined: 25 July 2008

Using a LeCroy DSO you can sit it up to trigger when the 1st wire breaks and then trigger again when the 2nd wire breaks.

If you use the sequence or segmented storage mode where it stores a set of samples from just before to just after each trigger event, the LeCroy timestamps the trigger times from a real time clock that is not directly running at the sample rate but is usually available at a much higher resolution. This will give you an extremely accurate time between the events.

So accurate that depending on the required precision of your measurements you may have to take account of propagation delays in your trigger circuits, monitoring cables and probes.

http://blog.teledynelecroy.com...cs-sequence-mode.html

This type of trigger may be available for other makes of DSO.



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Andy Fierman

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