Hi,

I have Rigol DS1052E oscilloscope. Without probes connected it shows 400mv in one channel and 1v in other channel. is that normal? if it isnot normal can i adjust it to show 0v? Thank you.

Imran

 

Channels set for AC or DC ?

You reading trace with respect to gnd reference symbol and grid or just grid ?

Still read the same after doing and auto acquire on vertical channel ?

Regards, Dana.

 

In addition to Dana's points:
- Short each input to ground and see if the readings go to 0V - floating inputs may measure anything from the ether.
- If they don't match, leave the oscilloscope turned on for about half hour and recheck - there is a chance it requires to warm up and get the appropriate amplitude, offset, etc.
- Whatever Dana mentioned about AC, DC, auto acquire, etc.
- I think this family of oscilloscopes has an auto calibration routine - this may help overcome any intrinsic offsets, but it is usually better if you wait for the half hour to do this.

 

Channels set for AC or DC ?

You reading trace with respect to gnd reference symbol and grid or just grid ?

Still read the same after doing and auto acquire on vertical channel ?

Regards, Dana.

Hi,
I have set the channels in DC coupling. and i am seeing 12mv

In addition to Dana's points:
- Short each input to ground and see if the readings go to 0V - floating inputs may measure anything from the ether.
- If they don't match, leave the oscilloscope turned on for about half hour and recheck - there is a chance it requires to warm up and get the appropriate amplitude, offset, etc.
- Whatever Dana mentioned about AC, DC, auto acquire, etc.
- I think this family of oscilloscopes has an auto calibration routine - this may help overcome any intrinsic offsets, but it is usually better if you wait for the half hour to do this.

i short input to ground and the readings dont change. what i notice is when i just start the oscilloscope the reading will be 0v and slowely it increases. after some time it reaches 1.7v and remains there. when i test my dc power supply this 1.7v is adding to the real value.

 

Sure sounding like front end of the scope, amps, attenuator, exhibiting
a problem. Any chance you applied out of spec V to inputs ?

Or scope V reference is hosed.

Regards, Dana.

 

That is my suspicion as well, especially due to the fact the offset increases as the equipment warms.

The schematic diagrams below will help - also, a can of freon that cools parts of the PCB to observe its behaviour.
http://rigol.codenaschen.de/index.php/Schematics

 

last week while i was working on amplifier my input and ground touch some very congested place and it spark very easy nothing big to talk about. i dont know that simple small touch will cause that.
i opened the oscilloscope just now and i found the fan is not working. while pulling i broke the on off switch. my bad. now i have to plug and unplug to use it. i just used some silicone spray on fan and it start to work. i dont know if i can fix the damage. i love my scope and without that it is almost tough to troubleshoot amplifiers.

 

Since the unwanted offset voltage adds to the input voltage by the time it makes it to the screen, I think it is likely that a large part of the scope is working OK.

The position signals are applied to one of the inputs of a variable gain amplifier with differential input and output. It looks like the position signals come from the decoded (as in routed) output of a PWM. There is a 2.5 volt reference used for the position signals. I didn't look carefully at the schematic, but I think those are the only PWM-derived signals that use that reference. This strongly suggests that it is that reference that is changing (and I suspect dropping in voltage) as it heats up. If it was heating because the fan wasn't working, I think it probably will not have suffered any permanent damage.

I would replace the fan with a new one.