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# 8V71

## Senior Member

#### Visitor Messages

Showing Visitor Messages 1 to 9 of 9
1. 03-31-2020 05:38 PM - permalink
stuiec
Glad to hear you're OK, sounds like a real rough go! I've not been on much either, though still back to get help now and then, and a bit more time on my hands lately.
2. 12-05-2018 11:44 PM - permalink
stuiec
Where you at buddy? Hope all's well!
3. 12-26-2013 10:55 PM - permalink
dronai
I took AC/DC theory about 25 yrs ago !! I just finished taking 4 MThs of college level DC theory with a lab. So I'm not really following everything you wrote. 10x probe, ok and my scope is an old analogue type that says nothing on the screen. So you double the number for peak to peak ! 170V is the peak of the wave form not the 120V RMS right ?
4. 12-26-2013 07:00 PM - permalink
8V71
There should be a scope probe calibration point on the scope somewhere so you can check the probe accuracy. If the calibration square wave is distorted there is a little adjustable capacitor on the probe that you can turn to sharpen up the square wave.

Also, in the middle of the large volts/division knob is a smaller knob that allows a fine adjustment. That knob has to be in the calibrated position (detent) for accurate measurements.
5. 12-26-2013 06:06 PM - permalink
8V71
Two problems....120 volts RMS (X1.414) equals about 170 volts peak. Double that for peak to peak for about 340 volts. A scope sees peak to peak for the full waveform.

Remember that I mentioned a 10X probe? You will measure 1/10th of the actual voltage. If you are using a Tektronix probe your scope will know that you are using a 10X probe and it should automatically adjust the volts per division to 50 when in the 5 volts per division setting. It sounds like the scope is adjusting 5 to 50 volts which is correct. Look on your display and it should say 50v per division. For the proper 340 volts (120 RMS) the waveform should be reading 6.8 divisions.

By the way, a scope is clumsy at measuring 60hz line voltage but it's great for looking at waveforms, which is why you bought it.
6. 12-26-2013 04:55 PM - permalink
dronai
Ok, on cycles I have 3.4 on the division marks x 5 ms/div = .017 and the reciprocal equals 60 for f

On the voltage though, I am reading maybe 6.2 on the screen x 5v or the highest setting on the clockwise dial setting which does not give me 120V ?? what's wrong here ? a setting of 20V x 6.2 would give me what I want to see.
7. 12-25-2013 07:30 PM - permalink
dronai
Thanks, I got that part figured out ! Happy Holidays to you to.
8. 12-25-2013 06:34 AM - permalink
8V71
I don’t know what special functions your scope has so I will talk about the similar scope that we have at work. The easiest way is to adjust your volts/division so the waveform fits comfortably in the display. Since you are dealing with relatively high voltage make sure you don’t exceed the max input rating of the scope. Start at the largest volts per division (all the way counter clockwise I think) and go from there. 60hz is about 16 milliseconds per cycle so adjust the sweep speed so you can easily measure it. At whatever sweep speed that you select, do the math and see if the complete cycle occupies about 16ms of time.

If you want to get fancy, turn on the vertical cursers. Move the cursers to exactly the start and end of one cycle and the scope will read the frequency for you. Your scope might display the frequency automatically or maybe has a built in counter? I just don’t know.

Merry Christmas or Happy Holidays dronai
9. 12-24-2013 11:01 PM - permalink
dronai
Allright, I got the scope today !!! I just have to figure out how to use it for HZ ? I only used one in class looking at the input from a Signal Generator. Can you help me get started, I want to test the output on that Generator.

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