PicoScope 7 Software
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GROSS ERROR IN D.C. AVERAGE MEASUREMENT IN PICOSCOPE
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Glovisol
- Advanced User
- Posts: 0
- Joined: Sat May 11, 2013 10:03 am
- Location: San Marzano Oliveto, Asti, Italy
GROSS ERROR IN D.C. AVERAGE MEASUREMENT IN PICOSCOPE
In Picoscope, depending on scan time, the D.C. average measurement can be correct, or can show a very big error.
I found this while monitoring 120 Hz PWM with a peak value of 3300 mV, but the same error happens at any frequency and at any level with a given ratio between Frequency and Pulse Duration.
I am enclosing two PC screens showing exactly the same PWM, but taken at different scan times, one showing the correct value and the other a grossly incorrect D.C. value.
I found this while monitoring 120 Hz PWM with a peak value of 3300 mV, but the same error happens at any frequency and at any level with a given ratio between Frequency and Pulse Duration.
I am enclosing two PC screens showing exactly the same PWM, but taken at different scan times, one showing the correct value and the other a grossly incorrect D.C. value.
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Re: GROSS ERROR IN D.C. AVERAGE MEASUREMENT IN PICOSCOPE
The DC average will only be for the data values drawn on the screen.
In the first trace only part of the third cycle is drawn, so a significant part of the zero level is missing. This results in the reading being higher than would be expected.
The second trace shows more cycles, so the incomplete part of the last cycle has less effect on the overall result.
In the first trace only part of the third cycle is drawn, so a significant part of the zero level is missing. This results in the reading being higher than would be expected.
The second trace shows more cycles, so the incomplete part of the last cycle has less effect on the overall result.
Martyn
Technical Support Manager
Technical Support Manager