C5 calibration on new version

[johng]

Jan,

I think there's some misunderstanding here. If you are able to modify the wave shape of both the 0.1 and 3.3 test signals by adjusting C3, this strongly suggests that SENSEL3 isn't being toggled properly.

If this is the case, then the C5/U1A circuit is *not* used at all. Modifying capacitor values wont change that.

John

[alphaseek]

Jan,

I think there's some misunderstanding here. If you are able to modify the wave shape of both the 0.1 and 3.3 test signals by adjusting C3, this strongly suggests that SENSEL3 isn't being toggled properly.

If this is the case, then the C5/U1A circuit is *not* used at all. Modifying capacitor values wont change that.

John

There may be two questions here. One is whether SENSEL3 works properly in normal operation. The other is whether it works properly during the calibration process. It seems it would almost have to work properly in normal operation, because otherwise high input voltages wouldn't display properly. But as I remember, the calibration process opertes in its own routine, and SENSEL3 might not be working there.

And I guess there's a third question as to whether any of this is different on the new boards and new firmware.

[jan]

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old version 0.1

[jan]

sorry for late reply ,

caps are ordered as my local shop is not so well assorted these "smd-days " ,
so i need to wait a couple of weeks to get a go at testing.


- and indeed there are several issues mixed up in this topic.

in the low settings ( when sensel activates C3 ) you can adjust 0.1 and 3.3 graph with C3
So , setting the sensitivity manual to a rather small setting despite the manual telling you otherwise.

When the sensel3 switches you are supposed to adjust graph by C5 , and i could not make that work on my 2 dso150's

[jan]

caps arrived ;

Firstly i tested C4 , real capacity is around 2,158 pF

then i verified the switching of the sel signals ;

50mV 1-L 2-L 3-H
1 V 1-H 2-H 3-L

so according to that the input should switch from C3 circuit to C5 circuit

i tested caps at C6 position going down 100 82 75 47 33 22 10 NO change in C5 settings visible
Then i went up 100 220 330 470 and again NO change in C5 settings visible


I am running out of ideas.....................


anyone ??

[jye1]

The waveforms posted on Aug. 09 look good.

It is normal that C3 can affect both 0.1V and 3.3V signals if the path U1A is selected. Since 3.3V is a very large signal for this path only a small portion of amplitude can be displayed. U1A is saturated under 3.3V input. So it is not suggested to use 3.3V signal to calibrate C3.