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Old 9th Dec 2017, 6:31 pm   #17
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Hameg HM208 Oscilloscope Timebase fault

Hi

Further Pics added:

Pic (f) Timebase set to 0.5us/cm

Pic (g) Timebase set to 0.2us/cm

Pic (h) The Add/Chop and Dual buttons depressed and an apparently normal display is shown even at low timebase speeds.

Pic (i) A 1kHz Calibration signal applied to CH1 input, Timebase set to 2us/cm

Pic (j) A 1MHz Calibration signal applied to CH1 input, Timebase set to 0.2us/cm.


Note how far off accuracy the trace is particularly in Pic (i) This signal is occupying approx 5.3cm so T = 10.6us, therefore f = 94.3kHz. The signal is meant to be 1kHz. I checked this calibration signal on my Scopex scope and all's well there.
The inaccuracy seems to improve as the timebase speed is increased. Its as if there's non linearity in the trace. I get the impression that the trace is being compressed at low timebase speeds.

Any further help with this will be much appreciated. Thanks.

Regards
Symon.
Attached Thumbnails
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Name:	(f) 0.5us per cm.jpg
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Name:	(g) 0.2us per cm.jpg
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Name:	(h) Add Chop and Dual buttons depressed.jpg
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Name:	(i) 1kHz Calibration signal 2us per cm.jpg
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Name:	(j) 1MHz Calibration signal 0.2us per cm.jpg
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