### Author Topic: what an oscilloscope recommended for a woman passionate about electronics?  (Read 39576 times)

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#### tggzzz

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #525 on: July 30, 2020, 08:28:50 am »
Good

If you ever get a signal generator, then it is worth setting up the scope as shown in your simulation and then simply varying the duty cycle. You will see how that changes the trace on the scope, and will begin to have a visceral feel for what's happening. Such playing around twiddling controls can be enlightening - and that's especially true when debugging real circuits.

If your simulation is real-time, you might be able to do that in the simulator.

Your next task will be to understand the limits of the averaging done by the AC coupling. You will find the scope has a "low frequency cutoff" in the specification; if the waveform frequency is above that cutoff, the averaging will be good. If it is lower (i.e. the period is longer) then the averaging will be imperfect and the imperfection will be visible as a "distorted" trace. (Mathematically it will be the input signal passed through a high-pass filter.)

yes of course, when I take a signal generator I will already have some basic notions and I will be able to experience what I have already learned.
I looked at the specs, I see a "low frequency response" =< 2Hz, maybe you mean this limit?

Quite possibly, but I'd have to see the surrounding context to be sure.
There are lies, damned lies, statistics - and ADC/DAC specs.
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #526 on: July 30, 2020, 08:35:58 am »
Charlotte
Now you are getting some good core understanding of scope use we need advance you further to using the power of a modern DSO.

Measurements.
At one time we lined up waveform to screen graticules and did mental calcs based on s/div and V/div settings to obtain measurements and for those of us used to working like that many of us still do.
However with the modern DSO we have a powerful Measurement suite where we can select just a few we need or engage all but the display becomes quite busy when all are used.

Probe Comp signal:
Here I have selected 4 that you might commonly use and assigned them all to a particular channel (ch4 SDS1104X-E) although you can select and have measurements displayed from more than 1 channel.
The multifunction control is used to scroll through the list and a press selects the measurement required and a brief description of what each does.

Further on these X-E's we can select Statistics to gather further info about each measurement.
Take note of the Mean measurement value.

I am happy that DSO do many mathematical calculations: this, however, also has a sad dark side, that is, machines replace our brains. If we look at modern children, they no longer make any mental calculations, they use the cellphone calculator ...
I suppose even retired electronic technicians are having a hard time seeing how oscilloscopes make life easier today

I had already seen these mathematical functions in the overview of the manual in the first pages, for now I have written on my text document only a few things, when I get to the paragraph that deepens this theme I study it better ..
Little by little I get there, and what I don't understand I ask you experts. You are very kind and helpful tutit, thank you

#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #527 on: July 30, 2020, 08:39:08 am »

Quite possibly, but I'd have to see the surrounding context to be sure.

it is reported in the vertical system specifications: it says "low frequency response" AC-3db / = <2Hz (at the bnc input)

#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #528 on: July 30, 2020, 08:52:57 am »
You are very kind and helpful tutit, thank you
tutit

tautech is shortened from my company name being the district Taupaki where I live in NZ and Technologies but if you insist call me tutit or even better just plain Rob.
When I have time I drop in here and offer screenshots from very similar DSO's so it's easier for you to understand.
I have been using and selling these X-E's for some years and know them very well so it's easy for me to provide good examples as your thread develops.

You must know this is already a well followed thread as you are not the only novice working hard to understand what you see on a scope display and why.
You like many others before you have come a long way from opening the box, pressing the power button and the Autoset and threads like this really help other novices too in their understanding of circuits and scopes.

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#### tggzzz

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #529 on: July 30, 2020, 09:11:43 am »
I am happy that DSO do many mathematical calculations: this, however, also has a sad dark side, that is, machines replace our brains.

Very true; you have the right attitude.

If you don't understand the mathematics and the concepts, then the arithmetical calculations are pointless - and probably misleading. Just using a convenient tool without understanding is cargo cult science or voodoo magic.

Quote
If we look at modern children, they no longer make any mental calculations, they use the cellphone calculator ...

Not necessarily true.

When my daughter was being taught arithmetic (~2000), I was impressed that they were no longer taught "the single true way" to do, for example, multiplication.

I was taught the times tables up to 12 (because there were  twelve pence in one shilling!), and beyond that it was the long multiplication algorithm.

My daughter was taught to visualise the numbers and how they fitted together, so that she could break a particular calculation into whichever simpler calculations were helpful. Thus 20*18 might be decomposed into 2*2*100-2*20. That gives a better "feel" for numbers than the simple algorithm, and enables mental "sanity checking".

OTOH, using calculators for normal operations is sensible; why do work that is better done by machines - provided you do understand what the machines are doing, and that what they are doing is sensible.
« Last Edit: July 30, 2020, 09:21:16 am by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #530 on: July 30, 2020, 10:15:18 am »
tutit

tautech is shortened from my company name being the district Taupaki where I live in NZ and Technologies but if you insist call me tutit or even better just plain Rob.
When I have time I drop in here and offer screenshots from very similar DSO's so it's easier for you to understand.
I have been using and selling these X-E's for some years and know them very well so it's easy for me to provide good examples as your thread develops.

You must know this is already a well followed thread as you are not the only novice working hard to understand what you see on a scope display and why.
You like many others before you have come a long way from opening the box, pressing the power button and the Autoset and threads like this really help other novices too in their understanding of circuits and scopes.

it had to be ...you are all very kind and helpful, thank you
it was not a nickname, but all that the translator has miserably wrong

of course I continue, until I get to the last page of the manual. On the forum, however, I will continue even beyond this manual, after all I am passionate about electronics, even if I still understand too little about it.
Thank you

#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #531 on: July 30, 2020, 10:20:30 am »

Very true; you have the right attitude.

If you don't understand the mathematics and the concepts, then the arithmetical calculations are pointless - and probably misleading. Just using a convenient tool without understanding is cargo cult science or voodoo magic.

Quote
If we look at modern children, they no longer make any mental calculations, they use the cellphone calculator ...

Not necessarily true.

When my daughter was being taught arithmetic (~2000), I was impressed that they were no longer taught "the single true way" to do, for example, multiplication.

I was taught the times tables up to 12 (because there were  twelve pence in one shilling!), and beyond that it was the long multiplication algorithm.

My daughter was taught to visualise the numbers and how they fitted together, so that she could break a particular calculation into whichever simpler calculations were helpful. Thus 20*18 might be decomposed into 2*2*100-2*20. That gives a better "feel" for numbers than the simple algorithm, and enables mental "sanity checking".

OTOH, using calculators for normal operations is sensible; why do work that is better done by machines - provided you do understand what the machines are doing, and that what they are doing is sensible.

to think well, are the older children who forget to have the brain and compensate with the calculator.
If the machine does the math for me, ok I accept it, but I have to understand the reason for those math. I hope it is evident in this discussion of mine, that I try to go beyond the calculation of the machine: otherwise some of my curiosities are not explained ...

#### tggzzz

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #532 on: July 30, 2020, 11:07:54 am »
If the machine does the math for me, ok I accept it, but I have to understand the reason for those math. I hope it is evident in this discussion of mine, that I try to go beyond the calculation of the machine: otherwise some of my curiosities are not explained ...

I suspect the reason people are helping you is because that is evident
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #533 on: July 30, 2020, 02:13:02 pm »
Compensation signal siglent - DC coupling - ok the average value was about 1.50vdc (also measured with multimeter at the signal socket).
Since I ate bread and fox this morning, I thought that setting AV coupling made me an average value of zero volts on the signal socket.

[attachimg=1]

then I woke up my head, and I realized that the cut of the DC voltage happens then, in the circuit inside the oscilloscope. So it is right that the multimeter always measures me a dc value of 1.50v.
I see, however, the oscilloscope detects an average value of about -9mv: this perhaps means that the DC current is blocked, but not 100%

#### tggzzz

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #534 on: July 30, 2020, 02:43:41 pm »
then I woke up my head, and I realized that the cut of the DC voltage happens then, in the circuit inside the oscilloscope. So it is right that the multimeter always measures me a dc value of 1.50v.
I see, however, the oscilloscope detects an average value of about -9mv: this perhaps means that the DC current is blocked, but not 100%

Scopes are not precision instruments; they are designed to show the shape of rapidly varying signals.

The capacitor inside the scope will block the DC completely.

The 0.6% difference will be due to measurement errors inside the scope, and could be due to many causes.

There might be a DC offset inside the scope's analogue front end. Check that by turning off the signal generator, and see if the reading changes.
It might be that the duty cycle isn't exactly 50%.
The ADC in the scope has a limited vertical resolution (i.e. bits), and it will have a slope and offset and non-linearity errors. Compare 0.6% and 9mV with the scope's specification; you will need to read carefully (see my .sig ).
There can be arithmetic "errors" due to the limited number of samples and vertical resolution. Some scopes measure what they display on the screen, not all the samples in its internal memory.

Summary: it is worth doing a few quick tests to rule out gross errors, but that kind of "error" looks to be within normal behaviour.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #535 on: July 30, 2020, 03:19:16 pm »
Scopes are not precision instruments; they are designed to show the shape of rapidly varying signals.

The capacitor inside the scope will block the DC completely.

The 0.6% difference will be due to measurement errors inside the scope, and could be due to many causes.

yes I know that they are not precision instruments, their work is another. Measuring with the multimeter beyond that capacitor, it should mark 0vdc.
The purpose of my intervention was not those -9mv, but having understood that the compensation output signal always makes the same average value (1.51) both with dc and with AC.

#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #536 on: July 30, 2020, 08:08:04 pm »
2 things to do to improve accuracy.
Ensure probes are perfectly compensated with zero overshoot, Charlotte's are not perfect.
Run Autocal in the Utilities menu after some 30 minutes warm up.

Further, any accurate measurement requires the scope to be powered ON for a while so any/all internal component temperature drift has stabilized and matches the last run of Autocal.
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #537 on: July 30, 2020, 08:58:46 pm »
2 things to do to improve accuracy.
Ensure probes are perfectly compensated with zero overshoot, Charlotte's are not perfect.
Run Autocal in the Utilities menu after some 30 minutes warm up.

Further, any accurate measurement requires the scope to be powered ON for a while so any/all internal component temperature drift has stabilized and matches the last run of Autocal.

I'm honest, when I did the calibration I acted after a few minutes that I had turned on the siglent.
In the first part of the manual I am studying, I have already come across these 2 items: Do self cal and quick-cal.
I have not delved into qaunto I will get there later when the manual will explain them better.
However, one question is spontaneous: the probe calibration procedure, reported in the very first pages of the manual, does not involve using these functions of the utily menu.
Are these two functions for further, more precise calibration?

#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #538 on: July 30, 2020, 09:27:59 pm »
2 things to do to improve accuracy.
Ensure probes are perfectly compensated with zero overshoot, Charlotte's are not perfect.
Run Autocal in the Utilities menu after some 30 minutes warm up.

Further, any accurate measurement requires the scope to be powered ON for a while so any/all internal component temperature drift has stabilized and matches the last run of Autocal.

I'm honest, when I did the calibration I acted after a few minutes that I had turned on the siglent.
In the first part of the manual I am studying, I have already come across these 2 items: Do self cal and quick-cal.
I have not delved into qaunto I will get there later when the manual will explain them better.
However, one question is spontaneous: the probe calibration procedure, reported in the very first pages of the manual, does not involve using these functions of the utily menu.
Are these two functions for further, more precise calibration?
Self Cal is a manually started internal self calibration and it's a good idea to run it after large temperature changes like winter to summer if you are not operating in A/C building.

Quick Cal is an automatic always ON running self adjustment to correct for temperature changes while the DSO is operating. It can result in brief pauses of responsiveness to controls however we can turn this feature OFF.

Probe compensation is a manual process we must undertake to give the best waveform step response on the display. (square edge with zero overshoot/undershoot.)
It does not matter the settings we use other than the probe compensation waveform must be completely on the display and I find 100us is the setting I use most to get accurate/best probe compensation adjustments.

The tiny changes of all/any of the above can impact on measurement accuracy.

Some example of how improper probe compensation can impact measurement accuracy.....note the P-P.

« Last Edit: July 31, 2020, 08:06:25 am by tautech »
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#### dietert1

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #539 on: July 31, 2020, 04:53:14 am »
I would check first  whether there is a specification for the calibration signal accuracy. There may be none and it's a bit misleading to assume an accuracy in the mV or uV.

Automatic characterization and compensation ot the scope signal chain as a whole is available in professional scopes. Separate probe and scope adjustment as used by simple scopes does not work very well at high frequencies above let's say 5 GHz. As someone wrote above: When you adjust the probe, you assume that the calibration signal remains constant, which is an approximation for low frequencies.

By the way: Does the calibration signal frequency change with timebase? I remember the Tektronix 2465 had that feature. The calibration signal could be used to check timebase calibration at all deflection speeds. Maybe for a digital scope that is less important.

Regards, Dieter

#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #540 on: July 31, 2020, 07:59:17 am »
Self Cal is a manually started internal self calibration and it's a good idea to run it after large temperature changes like winter to summer if you are not operating in A/C building.

Quick Cal is an automatic always ON running self adjustment to correct for temperature changes while the DSO is operating. It can result in brief pauses of responsiveness to controls however we can turn this feature OFF.

Probe compensation is a manual process we must undertake to give the best waveform step response on the display. (square edge with zero overshoot/undershoot.)
It does not matter the settings we use other than the probe compensation waveform must be completely on the display and I find 100us is the setting I use most to get accurate/best probe compensation adjustments.

The tiny changes of all/any of the above can impact on measurement accuracy.

Some example of how improper probe compensation can impact measurement accuracy.....note the P-P.

taut you have attached two images? the second pngxxxx8 I don't see it..

thanks for the explanation, when I get to the self and quick paragraphs I will have less problems understanding: self is a manual calibration to be implemented if the environment changes temperature; quick is an auto calibration that adjusts itself based on temperature.
But when you advised me to do a self-adjustment, what function were you talking about? quick cal?
Or did you advise me to simply repeat the probe calibration as per the first pages of the manual? (10x - 1000Hz compensation signal - auto setup button - probe compensation via the small screw)

currently this is how my probe (yellow) is calibrated:

[attachimg=1]

in your example Vp-p bounces about 0.34v, my signal bounces only 0.08v.
Should I reach a Vp-p equal to the amplitude value?
or can we also have a small range of wave angle deviation?

#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #541 on: July 31, 2020, 08:03:13 am »
I would check first  whether there is a specification for the calibration signal accuracy.
There isn't.
Quote
There may be none and it's a bit misleading to assume an accuracy in the mV or uV.
Yes of course however the probe compensation signal and how well a probe is compensated is only given as an example of how an improperly compensated probe can effect measurement accuracy.

Quote
Automatic characterization and compensation ot the scope signal chain as a whole is available in professional scopes. Separate probe and scope adjustment as used by simple scopes does not work very well at high frequencies above let's say 5 GHz.
5 GHz  good 500 MHz probes have HF compensation adjustments.

Quote
As someone wrote above: When you adjust the probe, you assume that the calibration signal remains constant, which is an approximation for low frequencies.
Yes as most scope work is LF the common 1 KHz probe compensation signal is adequate.

Quote
By the way: Does the calibration signal frequency change with timebase?

Not on any low price DSO's that I'm aware of.
Quote
I remember the Tektronix 2465 had that feature. The calibration signal could be used to check timebase calibration at all deflection speeds.
Really, that's very cool.
Still for it to be properly useful it too would need to be kept in calibration.

Of the good few CRO's I've fixed, used then flogged very few had provision to adjust the timing or amplitude of the probe compensation signal however we still used it as a sanity check.
I always yearned for one of the classic old Teks with the probe compensation loop that doubled as a current loop for setting/checking current probes.
Now we can buy these deskew fixtures the yearning has vaporized.

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#### tggzzz

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #542 on: July 31, 2020, 08:06:20 am »
Some example of how improper probe compensation can impact measurement accuracy.....note the P-P.

The probe compensation can definitely affect the peak-peak value. If it didn't then there would be something seriously wrong with the measurement!

With any remotely competent calibration signal the positive edge and negative edge should be identical.
With any remotely competent scope compensation circuit, the various capacitances should not be voltage dependent. (If they are, then you have other major problems!)
Given those, the positive compensation error (i.e. area under the overshoot or undershoot) should be identical.
In that case the mean value of an AC coupled signal should still be zero.

The calibration signal's duty cycle will affect the mean value. That would not affect the utility of the calibration signal when compensating a probe. On an old analogue scope I wouldn't expect a calibration signal to have exactly 50% duty cycle, but on a modern scope with lots of digital logic it is easier to generate a 50% duty cycle than not.
There are lies, damned lies, statistics - and ADC/DAC specs.
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #543 on: July 31, 2020, 08:14:39 am »
I would check first  whether there is a specification for the calibration signal accuracy. There may be none and it's a bit misleading to assume an accuracy in the mV or uV.

Automatic characterization and compensation ot the scope signal chain as a whole is available in professional scopes. Separate probe and scope adjustment as used by simple scopes does not work very well at high frequencies above let's say 5 GHz. As someone wrote above: When you adjust the probe, you assume that the calibration signal remains constant, which is an approximation for low frequencies.

By the way: Does the calibration signal frequency change with timebase? I remember the Tektronix 2465 had that feature. The calibration signal could be used to check timebase calibration at all deflection speeds. Maybe for a digital scope that is less important.

Regards, Dieter

it seems to me that the calibration signal has a constant frequency of 1khz regardless of the time base.

I would like to point out that I do not demand a millesimal calibration, I am a beginner: I have to worry more in understanding the functioning of the signals (some MV will not change my life)
thanks Dieter

#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #544 on: July 31, 2020, 08:17:28 am »
taut you have attached two images? the second pngxxxx8 I don't see it..
Fixed.
thanks for the explanation, when I get to the self and quick paragraphs I will have less problems understanding: self is a manual calibration to be implemented if the environment changes temperature; quick is an auto calibration that adjusts itself based on temperature.
Both help keep the instrument in top condition and providing best accuracy.
How you use them is entirely up to you however if we do a firmware update always run the SelfCal.
But when you advised me to do a self-adjustment, what function were you talking about? quick cal?
The manually started Self Cal. Maybe run it 2x/year or when you get results you think may be wrong. It takes a few minutes to complete so good to run when you need a coffee.
Or did you advise me to simply repeat the probe calibration as per the first pages of the manual? (10x - 1000Hz compensation signal - auto setup button - probe compensation via the small screw)

currently this is how my probe (yellow) is calibrated:
Your probe compensation could be just slightly better without that tiny overshoot.
The adjustment changes very slightly as the scope warms up so do it after the scope has run some 10+ minutes.
Should I reach a Vp-p equal to the amplitude value?
The P-P includes noise (trace width) so adds to the Amplitude value.
It is of little concern other than to know why they are different.

« Last Edit: July 31, 2020, 08:19:29 am by tautech »
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#### tggzzz

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #545 on: July 31, 2020, 08:18:41 am »
Quote
Automatic characterization and compensation ot the scope signal chain as a whole is available in professional scopes. Separate probe and scope adjustment as used by simple scopes does not work very well at high frequencies above let's say 5 GHz.
5 GHz  good 500 MHz probes have HF compensation adjustments.

My HP10020A 1.5GHz passive probes don't.
There are lies, damned lies, statistics - and ADC/DAC specs.
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#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #546 on: July 31, 2020, 08:37:01 am »

Fixed.

The manually started Self Cal. Maybe run it 2x/year or when you get results you think may be wrong. It takes a few minutes to complete so good to run when you need a coffee.

Your probe compensation could be just slightly better without that tiny overshoot.
The adjustment changes very slightly as the scope warms up so do it after the scope has run some 10+ minutes.

not fixed, but not a problem

Now I do this: I leave the oscilloscope on for at least 10 minutes, then I run self cal from utily ... and see if the compensation improves.
For now I do not intervene on the small screw of the probe.
Thanks taut

#### CharlotteSwiss

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #547 on: July 31, 2020, 09:09:04 am »
I ran self cal (after 15 minutes of operation, the manual says to do after 30 minutes). In fact, on the signal of the yellow Ch1 something has improved (before Vp-p it was 3.10).
My surprise, however, is on the pink Ch2: it has been a long time since I used it, but I noticed that the probe is not well calibrated, at least the horizontal signal seems to be climbing. I believe I have to intervene on the small probe screw in this case.

note the difference between the yellow and pink signals
« Last Edit: July 31, 2020, 09:10:35 am by CharlotteSwiss »

#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #548 on: July 31, 2020, 09:12:41 am »
Now I do this: I leave the oscilloscope on for at least 10 minutes, then I run self cal from utily ... and see if the compensation improves.
It won't. It doesn't work like that. Self Cal adjusts the scope internally and the analog input that the probe is compensated to match remains unchanged.

Quote
For now I do not intervene on the small screw of the probe.
This ^ is what you must adjust.
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#### tautech

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##### Re: what an oscilloscope recommended for a woman passionate about electronics?
« Reply #549 on: July 31, 2020, 09:14:03 am »
note the difference between the yellow and pink signals
Yes the probe on ch2 needs better compensation adjustment.
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