callibration

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aibelectronics

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what does it mean, exactly, when one says he's callibrating the time-base of his oscilloscope with a 50hz sine wave? could it be that the 'length' of the time-base / time axis would be the period of the sine wave?
 
aibelectronics said:
what does it mean, exactly, when one says he's callibrating the time-base of his oscilloscope with a 50hz sine wave? could it be that the 'length' of the time-base / time axis would be the period of the sine wave?
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The x-axis of a scope is time per division, the 50Hz mains voltage in the UK (although you DON'T have your location filled in!) is extremely accurate (at least long term), so you can adjust your scopes timebase calibration against the mains signal - assuming you have some reason to want to adjust it?.
 
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ah no! no! i'm not using it to measure the mains supply, it's a digital oscilloscope and the chips would fry at 220/110v mains supply, unless of course i get a reasonable voltage divider and series resistor for reducing the current.
the circuit is for measuring 'small signals' of less than 1khz.
 
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A x10 probe would normally be sufficent to measure mains voltages, depending on the scope specifications - assuming the scope isn't earthed of course 8) (see another thread!).

Anyway, I wasn't suggesting you wanted to measure mains! - only that the mains voltage would probably be the source of the 50Hz that you could use to calibrate the scope against - it could either be direct, or (more likely) from a low voltage transformer.

But, to be honest, it's not something you need to know about, there's little reason to want to attempt calibration of your scope - particularly as you know little about it.
 
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Thanks Nigel, I think I get it. Essentially by callibrating the time base with a 50 hz sine wave, for example, means making the time/x axis be of a dimension to adequately 'capture' the nature of the wave or other waves within its frequency vicinity. We might decide for example to make a 'box' or a unit to be equal to 5msec, a 50hz wave would therefore cover a cycle within 4 'boxes' (4 x 5msec = 20msec).

A problem arises when we measure a 5khz wave, for example, against this callibration as it would make several cycles within a single box. We then would have to alter the callibration to adequately capture it . So yes a time base callibrated against 50hz would be good for measuring mains supply and we wouldn't, if at all, need to change it very often, as we would not expect the frequency to vary very much.
 
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