I am trying to measure the voltage between 2 points using an oscilloscope and a multimeter.

Question 1:

I am getting a difference when I measure the voltage using an oscilloscope and using a multimeter in the order of 10mV and in some cases 100mV. I am using a ground clip when I use the oscilloscope as shown below. What might be the reason for the difference for this?

Question 2 :

Suppose I measure voltage between two points (both of which are not ground - differential voltage) using an oscilloscope, is using differential voltage probe the only way to measure the voltage between those two points (both are not ground,) or can I use a single probe with the ground clip (shown below) to measure the voltage between those two points (both are not ground) - Is it safe?

I perform this above test with 2 power supplies : Using a bench power supply to the power the board and in another case, I use a 12V lead acid battery to power the board.

The oscilloscope is connected to earth ground and the power supply through which the board is powered is also earth grounded. In another case, I am powering the board using a 12V lead acid battery alone, and the oscilloscope will be connected to earth ground.)

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  • 1
    \$\begingroup\$ Not enough info. For Q1 it might be normal to see different results with different measuring devices bevause they have different input impedance. What are you measuring, and how? Are scope probes in 1x or 10x mode? For Q2, the way to measure differentially depends on if the measured device has a connection to scope ground via any route like mains plug, or if it is floating regarding the scope ground. You can use two probes to measure differentially, depending on if the something is measurable without a special probe. \$\endgroup\$ – Justme Oct 13 at 5:04
  • \$\begingroup\$ Please split the question so you have one question per post. And if you get a 10mV difference and is measuring 100 volt its well within the calibration tolerance for most equipment, please specify the measured voltage and not just the difference. \$\endgroup\$ – Mats Karlsson Oct 13 at 7:11
  • \$\begingroup\$ For Q2, see electronics.stackexchange.com/questions/369223/… and techni-tool.com/site/ARTICLE_LIBRARY/… \$\endgroup\$ – Mats Karlsson Oct 13 at 7:12

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