help with energy concepts 30820 oscilloscope

AlbertHall

Joined Jun 4, 2014
9,311
How come w/o adjusting anything except voltage to 10mV (from 5mV to 10mV cal setup) I get scrolling signal? If I back trigging level off a bit, it stops.
Changes to the input signal, or input attenuator setting both affect the signal going to the trigger circuit. You will need to get used to adjusting the trigger level. 'Auto' should handle such changes better.
 

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neospam

Joined Jan 13, 2020
94
Changes to the input signal, or input attenuator setting both affect the signal going to the trigger circuit. You will need to get used to adjusting the trigger level. 'Auto' should handle such changes better.
how does auto work? Keep it from scrolling or to start it scrolling? Wondering if it works or not. I will need to go look that function up.
 
The difference, that may or may not be there will basically be "Imaginary" or a before and after picture, but the before picture will effectively be missing.

You want to set 0V to be one of the "lines" on the graticule. In esscence, where the bottom of the square wave is.

now, you want to look at the square wave to see if the bottom starts at 0V or does it start at some value greater than 0V.

.OR.

Look at the 0V level compared to the bottom part of your waveform.
 

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neospam

Joined Jan 13, 2020
94
I did get my function generator user manual today - ECI 40600 A little disappointed, it is more of a classroom booklet. It does have some good specs info in it and school book for me. I noticed the person selling them has a service manual for it and it does not show up in the regular search unless you type proper name in. They have it listed incorrectly, makes it harder to find.

Well at about a dollar a page I got the user manual - not useful. Now I should have really just purchased the service manual. Both are around 15 bucks.. so If I buy the service manual, I'll have 30 dollars in books on top of the machine, I paid 40-50 dollar range delivered. AND no cables..

I could have and prob still will a Chinese one for 50 bucks, that does everything. Might not be as accurate as ECI, but.
 

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AlbertHall

Joined Jun 4, 2014
9,311
how does auto work? Keep it from scrolling or to start it scrolling? Wondering if it works or not. I will need to go look that function up.
'Auto' kinda sets a trigger level automatically and works a lot of the time. Sometimes, with some signals, it won't work and then you need to set the trigger level manually.
 

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neospam

Joined Jan 13, 2020
94
The difference, that may or may not be there will basically be "Imaginary" or a before and after picture, but the before picture will effectively be missing.

You want to set 0V to be one of the "lines" on the graticule. In esscence, where the bottom of the square wave is.

now, you want to look at the square wave to see if the bottom starts at 0V or does it start at some value greater than 0V.

.OR.

Look at the 0V level compared to the bottom part of your waveform.
you are talking about the curved up area of the left side of the wave?
 

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neospam

Joined Jan 13, 2020
94
I am just talking..

When you test a low volt DC circuit live, do you hook your ground probe to circuit board ground? Sometimes case & circuit boards are the same?

Can I see dc data single coming out of a chip with this 20 mHz scope?
 
I don;t think anyone really knows what auto trigger means EXCEPT if no trigger exists in the displayed time, the scope triggers. This is why a DC signal gives you a trace. Auto trigger being stable is amplitude dependent. At low signal levels compared to the range, you likely will not get a stable trace.

This scope seems to be missing the "beam finder" control. This usually collapses and de-focuses everything.

"Trace rotation" is an Earth's magnetic field correction. It's used when the scope trace (GND) isn't flat. It has a slope to it.
 
you are talking about the curved up area of the left side of the wave?
The bottom should be flat. But, see we're learning how to use an oscilloscope unconventionally.

Your just trying to answer: Is there a DC offset in my calibrate waveform? I did not look at a plot of Vce vs Ic of the digital transistor in your calibrator.

Everyone will know where GND is and then when you apply the waveform without touching the vertical position, there may or may not be a small offset.
 
When you test a low volt DC circuit live, do you hook your ground probe to circuit board ground? Sometimes case & circuit boards are the same?
In general, do not use the GND clip. Usually there is a ground on the scope somewhere. When the circuit is isolated, your going to need to connect a ground. A better way would be get a BNC to banana adapter and use one of the other BNC connectors to get your reference.

Measure the AC and DC voltage between your circuits ground and the scope ground BEFORE making the connection. make sure it's zero or close to it.

The use of a short GND clip will sometimes clean up high speed signals.
 
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neospam

Joined Jan 13, 2020
94
I have no idea what your trying to say. Data like I2C requires a protocol analyzer.
I purchased this analog scope as a bench tool and to learn. If I continual to get deeper into elc I will get a more modern scope. Many bench people say to get an old analog and a new scope for your work bench. Newer style scope have come down considerably in the last several years. You can get a decent scope for 100-400 range.

After posting something about ground, I kind of forgot what AlbertHall said when I was probing the scope. Leave ground off and prob the one chip for a signal. It was on the wrong scale to see well, but I noticed it flashing slightly, that help me diagnosis what was wrong.

Just wondering where the limitations lay with this 20mHz analog scope.
 

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neospam

Joined Jan 13, 2020
94
This switch has seen some use. It is a little wiggly besides dirty. Anyone have any luck with tightening up a lose switch? Not sure it is accessible. Will clean it out, but its a little lose.
 

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tautech

Joined Oct 8, 2019
60
It could possibly be a wafer switch. Similar to rotary switches with exposed contacts. You wont know until you look.

You might be able to use some 1500 grit sandpaper.

I might be abe to send you a small amout of conducto-lube. https://www.cool-amp.com/conducto-lube The stuff is really expensive. Mine has dried up a bit. Need to find some mineral oil.
Certainly NOT or damage to the contacts may result.
Typically they have oxidised from lack of use and exercise is often enough to get them reliably functional again.
Deoxit is a widely recommended product for cleaning precision contacts and if they need be physically cleaned lint free paper and IPA is as rigorous as you can safely apply.
 
I already mentioned De-oxit. There are contact burnishing tools. 1500-2000 grit is pretty fine. I can get 2000 grit nearby: https://www.woodcraft.com/products/norton-9-x-11-sandwet-sanding-sheets-2000-grit-5-pack Agree, though, save the samdpaper for the last resort.

I forgot the dollar bill is another good burnishing tool It's great for cleaning flame sensors.

I had a power supply with a bad output relay in it, so I wrote a prgram to exercise the relay like 1x every 30s and ran it overnight. Problem solved in the morning.

Contacts should have a minimum "wetting" current which is the smallest current you should switch. It's usually on the order of 10 mA. Platings can lower that. I did design a current to voltage converter with mercury wetted relays for in-house use.
 
Just wondering where the limitations lay with this 20mHz analog scope.
So let's ask what do you want a scope for?


Clearly, it's good for audio and it was probably OK for NTSC troubleshooting.

Limitations:
bandwidth
Rise time - high rise time measurements are done with a dual timebase scope
You probably can;t see the trigger signal - A delay line or long piece of coax is sometime used inside the scope
Not a storage scope - DSO (Digital Storage Oscilloscope)
Not an MSO - Mixed signal Oscilloscope
Doesn;t have protocol analysis.

No "measurements"
No FFT (Fast Fourier Transform)

Nice features
v/division with a 10x probe is high
Dual trace so you can do pseudo differential measurements (A-B)

I never had the luxury of owning or using a "differential" or an "Active probe".

My goto scope at work was a battery powered CRT dual trace Tek 212 Oscilloscope with a bandwidth of about 200 kHz.

I hated a few Phillips scopes we had. The Trace was very wide.

We did have a Tektronix, 1 GHz bandwith scope I believe and a Tek medical imaging scope.
 
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