Author Topic: Rigol DS2072A voltages reading are off  (Read 1436 times)

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Offline AlphaRomeo

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Rigol DS2072A voltages reading are off
« on: February 17, 2017, 03:58:35 PM »
Hi folks,

I am new to the forum, and new to the Rigol Scope DS2072A, just got this puppy, so I am learning how to use it. One thing I notice so far is that the voltages reading are wrong, or I could be wrong. Anyway, I have one of those DC voltage reference device(cheap one, I think I paid 10 dollars or so), my Fluke 28II less than a year old indicates the correct voltages, the scope is way off. Out of four reading, one voltage(10V) is the only reading that is correct. The other three are way off.

7.5V the scope shows 7.78V
5.0 V the scope shows 5.28V,  wow!
2.5 V the scope shows 2.77V

Who is wrong here? I dont think is the Fluke. I got the voltage reference right after I got the Fluke, the Fluke has not changed the reading.

To have a better idea what I am talking  about, I attached some pics  to this post. Yes, I recalibrate the scope after I got it. I noticed the same with A/C voltages,  etc.

The scope reference voltage seems to be correct, I mean the square wave signal.

« Last Edit: February 17, 2017, 04:04:51 PM by AlphaRomeo »
 

Offline CustomEngineerer

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Re: Rigol DS2072A voltages reading are off
« Reply #1 on: February 17, 2017, 04:50:02 PM »
An oscilloscope is not a precision voltage measuring device so you should not expect it to be as accurate as your DMM. Also, the number in the top right corner  is the voltage level the trigger is set at, not the voltage the scope is measuring. I would strongly you spend some time reading the manual for your scope.
 

Offline AlphaRomeo

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Re: Rigol DS2072A voltages reading are off
« Reply #2 on: February 18, 2017, 03:01:29 PM »
Thank you for taking the time to reply. Yes, I am going through the manual right now. Good to know that the scope is not as accurate as my Fluke.

 

Online rstofer

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Re: Rigol DS2072A voltages reading are off
« Reply #3 on: February 18, 2017, 04:10:08 PM »
The button at the top left of the screen selects between horizontal and vertical measurements.  Once a group is selected, you will be able to select various measurements (like Vtop or Vbase or whatever) and display them on the bottom of the screen where you have all the "*******".  If Vbase is 0V then you can just look at Vtop for a DC measurement.

 

Offline flash2b

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Re: Rigol DS2072A voltages reading are off
« Reply #4 on: February 18, 2017, 07:20:31 PM »
If you want to measure DC on a scope, you get the best precision if the X-axis, equal 0V is at the bottom of the screen. Then select the lowest possible V/div attenuation value to match the level of the signal. This will bring out the best precision for the measurement. Your rigol can display 8 div's horizontal so with a V/div set to 1V, a 7.5V signal can be measured.

« Last Edit: February 18, 2017, 07:22:50 PM by flash2b »
 

Offline AlphaRomeo

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Re: Rigol DS2072A voltages reading are off
« Reply #5 on: February 23, 2017, 08:42:00 PM »
An oscilloscope is not a precision voltage measuring device so you should not expect it to be as accurate as your DMM. Also, the number in the top right corner  is the voltage level the trigger is set at, not the voltage the scope is measuring. I would strongly you spend some time reading the manual for your scope.

There is not question about that reading the manual and  playing with the instrument is the only way to get it. Yes, you are absolutely right, that is the trigger level  indicator. Somehow I was expecting that the scope was going to show me the voltage reading just like my DMM does, some kind of digital indicator, somehow  it does but not the way I expected plus is kind of off(some mili-volts) compare to my DMM.  As you said, is not as accurate as the DMM.

Pure DC voltage does not require trigger level, so I zero out the trigger level. I apply a DC voltage to  CH1, the scope indicates(Y axis) the voltage, I have to do the math to verify it. I dont like this.
If I want the trigger level to tell me that the voltage is what I expect, I move the trigger level to super-impose to the X-axis, bingo, now the trigger level tells me the DC voltage. What  a pain.

 



« Last Edit: February 23, 2017, 08:44:23 PM by AlphaRomeo »
 

Online MrW0lf

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Re: Rigol DS2072A voltages reading are off
« Reply #6 on: February 23, 2017, 09:07:34 PM »
Too lazy to read manual but... Cant you do on-the-fly DC level zero on this scope to iron out current calib error? There are DMMs and scopes that have this.
 

Offline bigeblis

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Re: Rigol DS2072A voltages reading are off
« Reply #7 on: February 23, 2017, 10:06:54 PM »
Use the button on the left side of the screen to open the measurement menu.
The measurement results are displayed below the waveform, and your device now turns on the frequency measurement.
 

Offline ProBang2

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Re: Rigol DS2072A voltages reading are off
« Reply #8 on: February 23, 2017, 10:12:37 PM »
[...]
If I want the trigger level to tell me that the voltage is what I expect, I move the trigger level to super-impose to the X-axis, bingo, now the trigger level tells me the DC voltage. What  a pain.
:palm:

Why you simply don´t RTFM?

The oscilloscope proceeds measurements of nearly everything. E.g. look at that screenshot from a DS1054 (the
little sister of your scope). Applied: 5 V DC on channel 1 (yellow) and 1.2 VPP AC, 500 KHz on channel 2 (blue).



 

Online DimitriP

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Re: Rigol DS2072A voltages reading are off
« Reply #9 on: February 23, 2017, 11:37:54 PM »
Quote
Why you simply don´t RTFM?
Twice!



   Don't be limited by your own imagination, because sometimes "it" means what you think it means. 
 


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