Dual Cursors, along with their statistics, are very useful. However, there are times when you do not want to analyze the total power consumption and/or current of the device during a time window, but the contribution of some individual component(s) at various times.
For example, in the screenshot below, a highly configurable touchscreen IC is operating in a periodic monitor mode, scanning for touches (there are two scans shown) while my uC is in STOP mode.
I was not interested in the total power consumed during a scan, but in the touchscreen IC’s contribution to it. I was adjusting parameters of the touchscreen to assess their effect on the power consumption.
It would be nice to be able to activate an additional ‘horizontal baseline’ cursor to establish the floor of the measurement instead of assuming 0 and measure (in this example) only the touchscreen IC’s contribution to power consumption due to the scans. I can think of many instances where that might be of interest.
I think that many instruments support this with a “null”, “tare”, or “zero” feature. In the case you shared above, you would see “negative currents” that are not really negative currents. Would a simpler “null” feature work for you in this case?
I can see the advantage of a “horizontal baseline” so that you still see the real current waveform. However, then all the statistics would be “wrong”. The UI would also need to very clearly indicate that the “horizontal baseline” mode was active for that waveform.
I’d want to adjust the baseline based on what I saw on-screen. In this case, I would set it to ~16 ma level, the ‘baseline’ from which I want to calculate the additional current, i.e. the area above the baseline and between two vertical cursors. I suppose it could also be done with a click and drag to form a bounding rectangle.
I added a baseline and a bounding rectangle to indicate what I’m interested in. The Joulescope is an energy analyzer, but why limit the analysis to total energy over some time window? The energy contribution of a periodic event can also be of interest, especially if modifications can be made to alter that event’s energy profile. Now I suppose if the baseline was always the same rock solid value, you could still make comparisons using dual cursors only to see if you’ve made improvements, but that might not always be the case.
I understand what you are trying to measure, and it makes sense to me.
In my mind, it fits under the larger category of state analysis for the device under test. The existing Joulescope UI allows you to measure and manually extract this data, but it does not do much to help automate the process. I have some things in mind. Unfortunately, it will have to wait until 2023.
I will keep this in mind as we improve dual cursors this year. The dual marker statistics are currently computed in a way that would make this feature more challenging than you would think. No promises, but I’ll see what we can do sooner rather than later!
