High offset in PicoLog?

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jcheriton
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Joined: Thu Nov 04, 2021 10:33 am

High offset in PicoLog?

Post by jcheriton »

Hi
I have just started using our DrDAQ to log current for a project by connecting the Scope input across a 1R resistor and logging the voltage.
I'm using a shielded BNC probe from my oscilloscope however, even with it shorted, I get a 10mV offset overlaid with quite a lot of noise on the logged voltage at the scope input. This is the same with the channel set to both LatestValue and Average.
As I shall be trying to log a project that uses from 0.9mA to 250mA while it's running, and I shall be logging it for several weeks, this 10mA noisy offset is going to affect the overall average current measured.
Obviously I can remove the offset from the final average current however is there some other solution that could lower the offset significantly?

Gerry
PICO STAFF
PICO STAFF
Posts: 1053
Joined: Mon Aug 11, 2014 11:14 am

Re: High offset in PicoLog?

Post by Gerry »

Hi jcheriton,

Sorry for the long delay in answering. I have been off work for different reasons, and only just caught up with a heavy workload, and backlog of Helpdesk tickets.

To answer your questions, you can remove the offset by clicking on the drop down arrow next to the Button/icon labelled 'Scope' for turning on the scale of the Scope, and then select Zero all Ranges, at the bottom (while ignoring the Prompt to short circuit the input).

Regarding the noise, you could first of all try practical solutions, such as moving your Design Under Test away from all possible sources of noise and/or shielding the DUT (e.g. with a foil lined box that is grounded). Regarding software tools, you could try adding a Math Channel Filter, adjusting the cut-off frequency, to give you the optimum reduction of noise, without minimal impact on the dynamics of the plotted data. Go here: for a reference on Math Channels, https://www.picotech.com/library/oscill ... h-channels and here: https://www.picotech.com/library/oscill ... h-channels for a reference on Math Channel Filters.

Regards,

Gerry
Gerry
Technical Specialist

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