Wrong voltage measurements, bad DC offset

[nyogo]

Hi!

I built the kit and before soldering components checked all the resistors, everything was fine(except one 150 Ohm resistor, I measured 142 Ohm).

The trace is not running on the center. When nothing connected, its way too below, also when measuring a 9V battery.
Same with the 3.3V test signal,a little bit weird when switching to 0.1V.
When displaying data on 9V battery measurement, totally wrong voltages shown.
Any idea?

9V measurement

no signal, 0V

test signal 0.1V

test signal 3.3V

[cdw2000]

The operating instructions are not real clear on this. You need to do a calibration. With the input switch set to GND, press and hold the V/DIV button for several seconds. You should see the trace center itself at the V/DIV marker on the left side of the display. Once this is done, release the button. The scope will remember this setting.

P.S. The 0.1 volt test signal does have a large DC offset. You need to use the AC coupling setting to be able to do the input adjustment called out in the instructions. JYE Tech indicated that this may be fixed in an upcoming firmware update.

JYE Tech should probably create a FAQ section for these kinds of questions (I'm just another customer lurking on the forum).

[nyogo]

Thanks cdw2000, you're my man
Did the calibration that way, now everything is perfect.

I think the same that JYE should create a FAQ in the forum or at least update the online User Manual with these little hints.
Since it's a kit, the first thing that comes to the users' mind in these cases that something went wrong during the assembly or some parts are defected.

[jye1]

Thank you for the suggestion. Will do shortly.

[boo]

The operating instructions are not real clear on this. You need to do a calibration. With the input switch set to GND, press and hold the V/DIV button for several seconds. You should see the trace center itself at the V/DIV marker on the left side of the display. Once this is done, release the button. The scope will remember this setting.

This calibration method does not work for me.
Switch to GND. Blue arrow left side near top of screen.
Hold down the V/DIV button. Nothing happens.
Turn rotary dial, blue arrow and trace move up and down.
But blue arrow is separated from trace by about 1/2 screen.

Tried many times.

[boo]

Follow-up on my inability to calibrate;

I tried turning the dial so the blue arrow at left was at bottom then kept turning. Then I long-pressed the V/DIV button. Nothing.
Then I tried the other buttons, and the blue box now would ONLY cycle between the SEC/DIV and TRIGGER pairs. I could no longer get the V/DIV pair to highlight.
I rebooted and blue box came up on the V/DIV 5mV highlighted and I could spin the dial to adjust. But when I pressed V/DIV nothing happened. Blue box didn't move.
I could no longer highlight the blue arrow at left. Mmmh. VERY strange.
I figured the button itself might be faulty so I opened up the machine and de-soldered it and tested with a multimeter.
Since it seemed to be doing things, and I didn't have a replacement button, I soldered it back in.

Now everything is working as expected. Yes, the long-press on V/DIV button aligns the GND trace with the left blue arrow.

SO: diagnosis - I must have had a bad solder joint on the button which was damaged/destroyed when I was first trying to calibrate. Just an unlucky coincidence.

All good now.