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Malfunctioning scope after incorrect input range setting

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Malfunctioning scope after incorrect input range setting

Postby wiik » Sat Feb 13, 2010 9:00 pm

Hello. I am using a PicoScope 4424 for long term monitoring by using available API.

By mistake, I set the input range to +/- 500mV, while the actual incoming signal was around +/- 3V and operated for a few minutes (due to not noticing the source of the error).

During this time several strange things happended in the following order:

- My logging application failed immediately when the wrongly ranged channel was connected.
- After disconnection of the wrongly ranged probe, a dc-offset occured on all channel.
- All probes were disconnected, still the PicoScope 6 application showed a dc-offset on all channels.
- The picocope was disconnected from computer and without power for a couple of minutes. The PC was restarted and PicoScope still showed a dc-offset on all channels.
- At this point, I concluded that the PicoScope needed repair.
- After 16 hours, the picoscope was started again, and the dc-offset dissappeared.
- After further 8 hours, the picoscope was tested with signal generator, and expected values was found. It is now unclear if I have a scope the functions sometimes and others not, or if the sequence was expected due to the wrongly ranged channel.

1. I am very curious knowing about what the expected consequence of a under-ranged input signal?

2. And also if I need to repair my oscilloscope or not due the described sequence of events?
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Re: Malfunctioning scope after incorrect input range setting

Postby PeterF » Fri Feb 19, 2010 10:06 am

I suspect that something in the input stage was overheated which caused a temporary DC drift. If all is well now, do not worry. If you have problems in future, you still have a full 5 year warranty, so you are still covered.
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