peak to peak value measurement

Post any questions you may have about our current range of oscilloscopes
Post Reply
daxesh
User
User
Posts: 3
Joined: Thu Oct 11, 2018 11:20 am

peak to peak value measurement

Post by daxesh » Thu Nov 01, 2018 11:20 am

Hello,

I am facing a problem for peak to peak measurement. I have an oscilloscope 2406B and using with Picoscope v6.13.6 on Windows 10. when I added a peak to peak measurement for signal measurement, it shows me double value of it. I have attachted a screenshot of it. It shows a right on the display, but wrong on measurement dialoge box. In the following screenshot I have set 1 Vpp and below you can see, it shows me 2.155 Vpp. probe is also on 1X. Is there any setting problem in software or what could be a possible cause of this ?
Please guide me to overcome it. Thank you

Regards,
Daxesh
Attachments
Picoscope Capture.JPG

Martyn
Site Admin
Site Admin
Posts: 3663
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: peak to peak value measurement

Post by Martyn » Thu Nov 01, 2018 11:26 am

That looks like ~2V Peak to Peak in both the display and measurement. What is the actual issue ?
Martyn
Technical Support Manager

daxesh
User
User
Posts: 3
Joined: Thu Oct 11, 2018 11:20 am

Re: peak to peak value measurement

Post by daxesh » Thu Nov 01, 2018 12:05 pm

Hello Martyn,
Sorry for my statement related to dialoge box, but I have set 1Vpp from function generator then why it shows me 2 Vpp on scope ?

Martyn
Site Admin
Site Admin
Posts: 3663
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: peak to peak value measurement

Post by Martyn » Thu Nov 01, 2018 1:18 pm

The settings in the generator are amplitude (Pk voltage) and offset, not peak to peak.
Martyn
Technical Support Manager

daxesh
User
User
Posts: 3
Joined: Thu Oct 11, 2018 11:20 am

Re: peak to peak value measurement

Post by daxesh » Thu Nov 01, 2018 3:09 pm

Hello Martyn,

I think you have misunderstood. Here I sent you the pictures of the function generator settings (set 1 Vpp)and the signal is given to other Oscilloscope and you can see it appears as ~1 Vpp. But why it appears 2 Vpp on picoscope ???
Please looking for some solution.

Kind Regards,
Daxesh

Martyn
Site Admin
Site Admin
Posts: 3663
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: peak to peak value measurement

Post by Martyn » Thu Nov 01, 2018 5:00 pm

I see no pictures of the function generator, hence the confusion. Can you repost them.
Martyn
Technical Support Manager

bennog
Advanced User
Advanced User
Posts: 53
Joined: Mon Nov 26, 2012 9:16 am
Location: Netherlands

Re: peak to peak value measurement

Post by bennog » Thu Nov 01, 2018 5:51 pm

This is because the function generator expects a load at the output (most times 600 ohm)
The internal resistor of the generator is also 600 ohm in this case.

Because you don't have a 600 ohm resistor at the output you don't have the voltage drop of the internal resistor. So with unloaded generator you get 2V top top ant with the 600 ohm you get 1V top top.

Benno

daxesh
User
User
Posts: 3
Joined: Thu Oct 11, 2018 11:20 am

Re: peak to peak value measurement

Post by daxesh » Fri Nov 02, 2018 8:37 am

Hello Martyn and Benno,

Thanks for reply. I have attachted that files but it doesn't posted, I don't know why.

Anyways, as you said about the voltage divider that make sense. But in this case internal resistance of generator is 50 Ohm but that make no difference becuase it will be divide by factor 2 (becuase of same output impedance and voltage divider rule) so it shows the half of generated voltage. as in the normal Oscilloscope,there is a setting to set 50 ohm oscilloscope resistance so that same voltage appearance on oscillosope. But in picoscope software, Is there any kind of setting to change its internal resistance while measurement so that it shows the same Vpp??

Thank you

Martyn
Site Admin
Site Admin
Posts: 3663
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: peak to peak value measurement

Post by Martyn » Fri Nov 02, 2018 9:17 am

That makes sense now, I though you were using our generator, so the voltage you see on our scope is 2V because the input impedance of our scope is 1 MOhm, whereas the signal generator will drive it's output so that you have 1V into a 50 Ohm terminated input.

You can either use a feed through 50 Ohm terminator on the scope, or you can create a Maths channel that performs the calculation to take account of the 1 MOhm input..
Martyn
Technical Support Manager

daxesh
User
User
Posts: 3
Joined: Thu Oct 11, 2018 11:20 am

Re: peak to peak value measurement

Post by daxesh » Fri Nov 02, 2018 10:24 am

Hi Martyn,

Exactly, that's what I am looking for.
Thank you. Have a nice weekend !

Best Regards,
Daxesh

Post Reply