PicoScope 7 Software
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Anomaly in Edge trigger
Anomaly in Edge trigger
I am using Picoscope 6.3.55.0 & 3224 hardware to capture turnoff waveforms, using both simple edge & advanced edge with hysterisis to trigger off the digital control signal rising edge of ch1, I also get triggers when the other channel 2 rising edge coincides (within nom. 300uS window) with the digital signal falling edge. So its capturing some turnons as well.
Ch2 is a current measurement across 1 ohm of a nominal 280mA load (250mA resistive, 29mA LED PFC Lamp operating off 110V 50hz AC.
The 110V supply is transformer isolated , the Logic board is Earthed & the Laptop is running off battery so there are no ground loops to interfere.
I dont miss any turnoffs, just get additional unwanted waveforms in the buffer (for later analysis & evidence)
Sample PSData file attached...
(PS: add file error "The extension psdata is not allowed.", I'll try zipping it up)
Thanks
Ch2 is a current measurement across 1 ohm of a nominal 280mA load (250mA resistive, 29mA LED PFC Lamp operating off 110V 50hz AC.
The 110V supply is transformer isolated , the Logic board is Earthed & the Laptop is running off battery so there are no ground loops to interfere.
I dont miss any turnoffs, just get additional unwanted waveforms in the buffer (for later analysis & evidence)
Sample PSData file attached...
(PS: add file error "The extension psdata is not allowed.", I'll try zipping it up)
Thanks
- Attachments
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- 20100518-0001.zip
- (182.8 KiB) Downloaded 423 times
Re: Anomaly in Edge trigger
Hi,
We cannot setup the same experiment as you, as it is not a recommended way to measure such voltages. It looks like you are probably getting some sort of coupling. I would recommend using something like a differential oscilloscope probe.
http://accessories.picotech.com/active- ... robes.html
Kind regards
We cannot setup the same experiment as you, as it is not a recommended way to measure such voltages. It looks like you are probably getting some sort of coupling. I would recommend using something like a differential oscilloscope probe.
http://accessories.picotech.com/active- ... robes.html
Kind regards
Ziko
Technical Specialist
Technical Specialist
Re: Anomaly in Edge trigger
Thanks ziko for the reply,
You might be right, there is probably enough parasitic capacitance in the isolating transformer & my setup to affect the 3224.
The logic circuit actually is not earthed as I stated, it is powered from a topward dc bench supply & Vicor DC-DC converters so has double isolation from the mains supply.(but is sitting on the bench in metal frame) .The laptop is mounted on an insulating base.
We have a job coming up soon where we should be able to purchase an isolated differential probe. I will repeat the test & advise results.
Tonig
You might be right, there is probably enough parasitic capacitance in the isolating transformer & my setup to affect the 3224.
The logic circuit actually is not earthed as I stated, it is powered from a topward dc bench supply & Vicor DC-DC converters so has double isolation from the mains supply.(but is sitting on the bench in metal frame) .The laptop is mounted on an insulating base.
We have a job coming up soon where we should be able to purchase an isolated differential probe. I will repeat the test & advise results.
Tonig