Tools: Measuring DC Over Time

[ACharnley]

Yo,

(title should read DC over time) It does now! Moderator

Until now I've managed to avoid getting deep with oscilloscope functionality, but that day has come, I think.

I have an DC circuit which is rectified AC charging a super-cap and need to measure voltage increase over time. It's low frequency (50Hz) and low voltage (< 20V). Ultimately I need to assert that the super-cap (which is 5.5V rated) is over-loading the power supply and preventing > 5V spikes from coming through.

I have a Handtek DSO-6022 USB oscilloscope and a Hantek DSO5102P on the way. When I fire up the Linux based OpenHandtek I'm presented with the screen below. The red light indicates the current voltage, but (first question) how do I determine what it is? I was expecting to see some X/Y values to be able to read it off.

Second question, the controls on the right change the red line much but display a white "noise" signal as shown in the second screenshot. Ideally it's the red line I'm interested in, I need to zoom into a portion of it to see what's going on there. I suspect this is what the white line is but I can't make it behave.

Your help much appreciated!

Andrew

 

[ACharnley]

Ah, am I using the wrong device? perhaps **broken link removed**

 

[JimB]

I am not familiar with Hantek equipment, but look at the bottom right hand corner of the screen, CH1 is ticked for Spectrum.

Could it be that the white trace is an FFT spectrum display of what is in channel 1 ??

Ah, am I using the wrong device?

Depending on how fast you expect the voltage to change, a voltmeter logged to a PC could be a better solution.

My bench multimeter a Fluke 8840A, has an IEEE 4888 interface.
Using a suitable driver (hardware and software) can plot voltage changes over a period of hour or days.

JimB

 

[ACharnley]

Quite fast, the AC to DC isn't a perfect sine. I've come across the Instrustar isds205a which looks promising. I've seen a few USB multimeters but they tend to output only a few times per second.