About Differential Probe Offset Adjustment

Embedded Security ChipWhisperer Hardware
1

Hi

The problem that I have is that the offset of the output shifts.
It seems that the offset shifts progressively over time.

Here the description of the measurement setup:

I’m using a SAKURA-G board with the differential probe at VCC shunt on the 1.2 V rail.
The differential probe is connected to an oscilloscope.
The differential probe is powered by + - 5 V.
Before starting the measurement the target implementation is executed and the offset is adjusted to put it around zero, ensuring that the two feedback leds are off.
The power consumption signal is 16 mV (Vpp).

What do you recommend to have a fixed offset ?

2

Hello,

Hmm - the offset shifts over a few days, or hours, or when are you seeing this?

If connecting to an AC-coupled output (such as CW-Lite) this shouldn’t really matter… there will be a small shift in offset, but as long as it’s kept well away from the rails won’t affect anything. If using a DC-coupled scope you may notice the shift more dramatically.

The offset is also dependent on the power supply for referencing, so if your power supply is drifting this will also happen!

-Colin