Results from 2 different Joulescopes


I currently own two JS110 tools and when I measure on the same PCB, I do not get the same results.
For example:
If I use JS1 with current range 18mA I measure 8uA.
If I use JS2 with current range 18mA I measure 6.7uA. (-1.3uA compared to JS1)

But then when I change the current range to auto I measure:
With JS1, 8.8uA.
With JS2, 11.5uA. (+2.7uA compared to JS1)

I understand that current difference that is caused because of the current range, so this is out of the question. What I do not understand is the current difference of the two JS in both occasions.

In attached I post the autoscale measurements with the two joulescope, just for reference.
Is there a way to somehow calibrate the devices?
Thanks in advance!

Hi @alexxx

First, your Joulescopes are already calibrated. While we do provide a validation procedure in the Joulescope User’s Guide Section 16.1, I doubt that is the issue. Just for reference, here is your previous post on current ranges. However, let’s start there.

Let’s confirm that your Joulescopes measure the same static current. I am going to assume that you have a power supply (PS), Joulescope A (A), Joulescope B (B), and a 1 MΩ resistor. If you don’t have a 1 MΩ resistor, you can often use a multimeter or oscilloscope input, which typically have a 1 MΩ to 10 MΩ input impedance. Connect the following:

  • PS.+ to A.IN+
  • A.OUT+ to B.IN+
  • B.OUT+ to 1 MΩ.+
  • 1 MΩ.- to PS.-

Now, power on your supply to +1V and start two Joulescope UI instances. Using the Device menu, select A in one and B in the other. Select Current Range to auto for both. What is the difference between the measurements?

Now, set both Joulescopes to the 18 mA range, but don’t change anything else. What is the difference between the measurements?

Now, use this same setup, except replace the 1 MΩ resistor with your target device. Set both Joulescopes to Current Range auto. What is the difference between the measurements?

With the dynamic data, you have to be very careful to get the same activity, otherwise your measurements will naturally differ because you measure different things. It looks like your data has some pattern that repeats every 5 seconds. When comparing data, add dual markers to measure over an exact number of these patterns. Does that change the result?

If not, I think that we need to look into the accuracy you should expect for your specific measurement. I am happy to take a more detailed look at your specific data. Could you share two JLS captures, one with Current Range set to auto and one with Current Range set to 18 mA? You can post using your favorite file-sharing method. If you would prefer to not share publically, you can email support at with the links to the files and this post.

Hi @alexxx - Thanks for the direct email. I replied by email on Monday. I am following up here since I haven’t heard back, and I want to confirm that you received my email. I will also send the email as a direct message on this forum in case my response was blocked somehow.

Hello Matt!

No no I received it, but I had an urgent task that drained all my time the previous couple of days. I will reply most probably tomorrow.


Great! No worries, and no rush. Just wanted to make sure it wasn’t a problem with email delivery.

This issue was closed successfully! Both Joulescope are measuring the exact same consumption now. The key was the proper settings from the JS software.

In file->preferences->Device->Settings:

buffer_duration = 1 min
sampling_frequency = 2MHz

Those settings applied for both Multimeter and Oscilloscope (can be selected by the profile tab).

So thank you so much mliberty for your support!

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