Author Topic: Oscilloscope Probe Opinion  (Read 2441 times)

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Offline joeqsmith

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Re: Oscilloscope Probe Opinion
« Reply #25 on: February 24, 2019, 07:37:33 pm »


I've thought about buying one of these wideband HV probes from MICSIG just to see how well they perform.
It would be very interesting to watch your evaluation.

I would most likely transient test it after I was done with everything else just to get an idea how it compares with some of the handheld meters I have looked at. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline cowasaki

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Re: Oscilloscope Probe Opinion
« Reply #26 on: February 24, 2019, 08:02:33 pm »
Thanks to all that have replied. Your response was much appreciated!!!

joeqsmith stated:  "If it were me and I wanted to look at the AC lines with a scope, which I have done, I would use a decent transformer"

I've been looking at and I think I'm about ready to pull the trigger on a variable isolated AC power supply. http://www.bkprecision.com/products/power-supplies/1655A-150v-3a-ac-power-supply.html

Based on your comment, I'm thinking I could also utilize the transformer's isolated output to safely check a 120 VAC line by varying the output to say maybe 15 VAC. Is this true? OR, for the sake of safety, is it still best I use a high voltage differential probe as described (possibly the Micsig DP10013)?

It would be great if I'm understanding you correctly, as I could then easily put the funds needed for a HV differential probe towards the variable isolated power supply.

That's a shed load of dosh though!  I wanted to build a variable AC supply but have been racking my brain over how best to accomplish it for months.  A transformer with 4 different outputs and a set of relays was an option but not very adjustable or convenient so my current favourite idea of making a decent 50Hz or 60Hz sine wave and then amplifying it to get the correct voltage and current appears to be the favourite.

Unless someone has a better idea......
 

Offline james_s

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Re: Oscilloscope Probe Opinion
« Reply #27 on: February 25, 2019, 06:57:34 am »
If you want a variable AC power supply why don't you just buy a variac? Or do you need arbitrary frequency?
 

Offline cowasaki

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Re: Oscilloscope Probe Opinion
« Reply #28 on: February 25, 2019, 08:41:26 am »
If you want a variable AC power supply why don't you just buy a variac? Or do you need arbitrary frequency?

It would be helpful to switch frequencies but also current limiting. I think it should be quite doable
 

Offline macboy

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Re: Oscilloscope Probe Opinion
« Reply #29 on: February 25, 2019, 07:58:39 pm »
Thanks to all that have replied. Your response was much appreciated!!!

joeqsmith stated:  "If it were me and I wanted to look at the AC lines with a scope, which I have done, I would use a decent transformer"

I've been looking at and I think I'm about ready to pull the trigger on a variable isolated AC power supply. http://www.bkprecision.com/products/power-supplies/1655A-150v-3a-ac-power-supply.html

Based on your comment, I'm thinking I could also utilize the transformer's isolated output to safely check a 120 VAC line by varying the output to say maybe 15 VAC. Is this true? OR, for the sake of safety, is it still best I use a high voltage differential probe as described (possibly the Micsig DP10013)?

It would be great if I'm understanding you correctly, as I could then easily put the funds needed for a HV differential probe towards the variable isolated power supply.

That's a shed load of dosh though!  I wanted to build a variable AC supply but have been racking my brain over how best to accomplish it for months.  A transformer with 4 different outputs and a set of relays was an option but not very adjustable or convenient so my current favourite idea of making a decent 50Hz or 60Hz sine wave and then amplifying it to get the correct voltage and current appears to be the favourite.

Unless someone has a better idea......

A signal generator to produce the 50 or 60 Hz sine signal, into an audio amplifier, into a suitable line transformer. E.g. for a 100 W audio amp, you would want roughly a 28 VAC output transformer, used in reverse (driving the secondaries and taking output from the primaries). If it has true dual secondaries then you can drive both of them, one with each channel of a stereo amplifier (but ensure close inter-channel level matching). If it has dual primaries, then you can wire it for 120V or 240V nominal output as needed. You get fine control of the frequency and amplitude, plus you have full isolation due to the use of a transformer.   I think most of us have an old outdated receiver or amp sitting in a closet, and a box full of various power transformers. Or it is just me?  ::)
 

Online 2N3055

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Re: Oscilloscope Probe Opinion
« Reply #30 on: February 25, 2019, 09:05:28 pm »
What does it has to do with oscilloscope probes, this current discussion on frequency converters? I'm confused. Why frequency converters?
 

Offline james_s

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Re: Oscilloscope Probe Opinion
« Reply #31 on: February 26, 2019, 04:50:59 am »
A signal generator to produce the 50 or 60 Hz sine signal, into an audio amplifier, into a suitable line transformer. E.g. for a 100 W audio amp, you would want roughly a 28 VAC output transformer, used in reverse (driving the secondaries and taking output from the primaries). If it has true dual secondaries then you can drive both of them, one with each channel of a stereo amplifier (but ensure close inter-channel level matching). If it has dual primaries, then you can wire it for 120V or 240V nominal output as needed. You get fine control of the frequency and amplitude, plus you have full isolation due to the use of a transformer.   I think most of us have an old outdated receiver or amp sitting in a closet, and a box full of various power transformers. Or it is just me?  ::)

My friend used a large audio amplifier to do that a few years ago, it worked however the amp despite being rated for something like 300W RMS it overheated and blew up twice at considerably less power. He replaced that with a proper AC supply which is similar in essence, linear amplifier in a huge rackmount thing with rows of TO3 transistors on an enormous heatsink.
 


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