AC RMS difference of Real-time and psdata saved

Forum for discussing PicoScope version 6 (non-automotive version)
Post Reply
fcx6y
Newbie
Posts: 0
Joined: Sat Jun 10, 2017 3:58 am

AC RMS difference of Real-time and psdata saved

Post by fcx6y » Sat Jun 10, 2017 4:09 am

I am using PicoScope 6 with 4262.
As shown in the picture, the real-time AC RMS measurement result is 1.331mV, while the AC RMS of the same waveform saved as psdata is 3.514mV. I also save data as .csv and calculate with excel. The result is also 3.514mV, the same as the one saved as psdata. So is the real-time AC RMS measurement incorrect?
Attachments
存储波形.png
psdata saved AC RMS
实时采样.png
Real-time AC RMS

bennog
Active User
Active User
Posts: 33
Joined: Mon Nov 26, 2012 9:16 am
Location: Netherlands

Re: AC RMS difference of Real-time and psdata saved

Post by bennog » Sun Jun 11, 2017 8:06 am

Taht is because the realtime RMS was calucated over the last 20 captures.
capture count colum.
The saved value shows 1
The realtime value shows 20.

Benno

fcx6y
Newbie
Posts: 0
Joined: Sat Jun 10, 2017 3:58 am

Re: AC RMS difference of Real-time and psdata saved

Post by fcx6y » Sun Jun 11, 2017 2:51 pm

bennog wrote:Taht is because the realtime RMS was calucated over the last 20 captures.
capture count colum.
The saved value shows 1
The realtime value shows 20.

Benno
I use save all psdata, which contain 15 waveforms. The AC RMS of each waveform is the almost the same, which is about twice of the real-time AC rms. And the signal I give is constant, the real-time AC RMS also change only slightly over the time.
So can you explain why the real-time AC RMS value calculated over the last 20 captures is only about half the saved value?

Best Regards,
Yu-Meng

Martyn
Site Admin
Site Admin
Posts: 3345
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: AC RMS difference of Real-time and psdata saved

Post by Martyn » Tue Jun 20, 2017 8:50 am

Can you post the actual psdata files so we can take a look.
Martyn
Technical Support Manager

fcx6y
Newbie
Posts: 0
Joined: Sat Jun 10, 2017 3:58 am

Re: AC RMS difference of Real-time and psdata saved

Post by fcx6y » Tue Jun 20, 2017 2:49 pm

Martyn wrote:Can you post the actual psdata files so we can take a look.
The psdata files are too big, The maximum allowed size is 512 KiB. Can you give me your email address? So i can send you the psdata files.
Attachments
pico 50欧短接 saved.png
saved
pico 50欧短接 realtime.png
realtime

Martyn
Site Admin
Site Admin
Posts: 3345
Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: AC RMS difference of Real-time and psdata saved

Post by Martyn » Wed Jun 21, 2017 5:04 am

The email address is support@picotech.com if you just use Save Current Waveform it will help to keep the size down
Martyn
Technical Support Manager

fcx6y
Newbie
Posts: 0
Joined: Sat Jun 10, 2017 3:58 am

Re: AC RMS difference of Real-time and psdata saved

Post by fcx6y » Wed Jun 21, 2017 12:32 pm

Martyn wrote:The email address is support@picotech.com if you just use Save Current Waveform it will help to keep the size down
I have sent the psdata files via email.
The size of the save current waveform is also 1061KB.
You can see from the save all waveforms file that the AC RMSs of all 15 waveforms are nearly the same.

Post Reply