Hi, my DSO138 measure wrong values. My normal offset is -5V. I meassure all test pads etc. And I trace problem to V-Mon voltage ( maybe ) .. In attachement you can find my meassurement ..
I try:
flash firmaware
resolder what was possible
Do you have any idea what is wrong ? ( Testing voltage the same as manual 9.3V all other test pins have good voltage by manual ..) Thanks for help
Problem with V-Mon and meassure offset
Problem with V-Mon and meassure offset
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Re: Problem with V-Mon and meassure offset
The -10 volts at TP25 (V-) is OK as long as the voltage at -AV is -5 volts. The -10 volts is regulated to -5 by U4.
What test point are you referring to when you say you have a normal offset of -5 volts?
What do you see that tells you something is wrong?
What test point are you referring to when you say you have a normal offset of -5 volts?
What do you see that tells you something is wrong?
Re: Problem with V-Mon and meassure offset
If I turn on my DSO138 and do not connect my probe to anything my measurements are -5V (value line at the display). If I connect it to +9V I get values just about +4V.. also If I try to connect it to Arduino PWM ( +5V) my measurements are about +2V- So all values on display ( alse info values (hold hold button for few sec)) are with -5V offset.
Re: Problem with V-Mon and meassure offset
The voltage at test point V2 should be about 1.66V, a few tenths off is OK.
If that voltage is alright try doing a factory reset and the Vpos Alignment.
I have had the settings in my DSO138 suddenly change for no reason and give similar problems.
Restore Factory Default
Hold down [+] and [-] buttons simultaneously for 2 seconds.
Vpos Alignment
This is to fix the mismatch between 0V trace and VPos indicator. To do this set couple switch [CPL] to GND position.
Press on [SEL] button to make VPos indicator highlighed. Hold down [OK] button for about 2 seconds. You will see
VPos indicator aligned to 0V trace when you release [OK] button. You may see some residue mismatch remains at
the highest sensitivity settings. This is normal.
If that voltage is alright try doing a factory reset and the Vpos Alignment.
I have had the settings in my DSO138 suddenly change for no reason and give similar problems.
Restore Factory Default
Hold down [+] and [-] buttons simultaneously for 2 seconds.
Vpos Alignment
This is to fix the mismatch between 0V trace and VPos indicator. To do this set couple switch [CPL] to GND position.
Press on [SEL] button to make VPos indicator highlighed. Hold down [OK] button for about 2 seconds. You will see
VPos indicator aligned to 0V trace when you release [OK] button. You may see some residue mismatch remains at
the highest sensitivity settings. This is normal.
Re: Problem with V-Mon and meassure offset
Hi, I try a factory reset and Vpos alignment. .But it still does not work right.
If I connect the probe to 8.03V on an oscilloscope I see just about 4.2V more in the attachment.
If I connect the probe to 8.03V on an oscilloscope I see just about 4.2V more in the attachment.
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Re: Problem with V-Mon and meassure offset
If the trace did not go to zero after the resets and you have about 1.66V at V2 I don't know what else to suggest.
Maybe it would be worth loading the latest firmware, especially if you don't have version -65.
You will find it here:
https://www.jyetech.com/forum/viewtopic ... t=10#p4251
113-13801-065.rar is in the Sept 03 post.
If the trace did zero but doesn't move the correct number of volts/division that's something that could be tracked down.
Maybe it would be worth loading the latest firmware, especially if you don't have version -65.
You will find it here:
https://www.jyetech.com/forum/viewtopic ... t=10#p4251
113-13801-065.rar is in the Sept 03 post.
If the trace did zero but doesn't move the correct number of volts/division that's something that could be tracked down.
Re: Problem with V-Mon and meassure offset
Hi yes .. Trace go to zero after Vpos aligment. If I connect probe 8V supply trace go just to 2,5V as in my previous screenshot
Re: Problem with V-Mon and meassure offset
There may be a bad connection, a solder short or parts may be in the wrong position.
Set the switches to DC, 1V, X5.
Touch the test leads to the 9V battery.
The voltage at V1 should be 1/100th of the input with the switches set as above. Expect about 0.08V at that point.
Change from 1V to 0.1V. The voltage at V1 should be 1/10th of the input, 0.8 volts
If the readings are not correct measure R1 through R5. R3 is affected by resistors in parallel so it will read a little low.
R1 100K R2 1 meg R3 190K (200K) R4 1 meg R5 20K
If V1 is OK then check V2. Set the switch back to 1V.
The voltage at V2 should increase about 0.13V when you connect the battery to the input.
R6 300 R7 180 R8 120
The labels for these resistors are under the part.
R9 1K R10 1.7K (3K) R11 148 (150) R12 120
Set the switches to DC, 1V, X5.
Touch the test leads to the 9V battery.
The voltage at V1 should be 1/100th of the input with the switches set as above. Expect about 0.08V at that point.
Change from 1V to 0.1V. The voltage at V1 should be 1/10th of the input, 0.8 volts
If the readings are not correct measure R1 through R5. R3 is affected by resistors in parallel so it will read a little low.
R1 100K R2 1 meg R3 190K (200K) R4 1 meg R5 20K
If V1 is OK then check V2. Set the switch back to 1V.
The voltage at V2 should increase about 0.13V when you connect the battery to the input.
R6 300 R7 180 R8 120
The labels for these resistors are under the part.
R9 1K R10 1.7K (3K) R11 148 (150) R12 120
Re: Problem with V-Mon and meassure offset
Hi all values looks ok ..
V1 is ok
V2 (DC,1V,X5) = 1.5V (at 8.07 Input)
V1 is ok
V2 (DC,1V,X5) = 1.5V (at 8.07 Input)
Re: Problem with V-Mon and meassure offset
If V2 changed from the nominal 1.66V to 1.5V when you connected the 9V battery the trace ought to be at the bottom of the display.
V2 should be changing from 1.66V to 1.73V
I see in the Dec 04 photo the display says the switches are set for 2V. The trace is one division above the center which says there is 2V input.
The trigger level reading in the upper right says 4.02V but that's not related to the input.
Let's double check what's happening.
DC, 1V, X5
Do you see 5V in the lower left corner?
With no voltage in is the trace on the center division?
When you connect your battery (actually 8V volts) the trace should go up 1.6 divisions. ( 5V/div times 1.6 = 8V)
V2 should be changing from 1.66V to 1.73V
I see in the Dec 04 photo the display says the switches are set for 2V. The trace is one division above the center which says there is 2V input.
The trigger level reading in the upper right says 4.02V but that's not related to the input.
Let's double check what's happening.
DC, 1V, X5
Do you see 5V in the lower left corner?
With no voltage in is the trace on the center division?
When you connect your battery (actually 8V volts) the trace should go up 1.6 divisions. ( 5V/div times 1.6 = 8V)