Use an oscilloscope to measure a small signal

Let’s talk about the requirements first. I want to measure a small signal and want to know the peak value, length, etc. of the signal. Then I built an amplifier circuit and copied it.

I first measured using the DS100 of Positive Atom, and then used the Keysight InfiniiVision 2000 X to measure.

I originally had a good oscilloscope on hand, but it was too big, and it was not a personal item, and it was useless to give me too precise measurement results. Well, I just wanted to buy a small oscilloscope to play with, because I bought it from him. The power supply and soldering iron seem to be of good workmanship and are OK to use.

This power supply deserves a lot of criticism, so I'll take the time to criticize it.

In fact, there was also a 1GHz and Mengyuan Technology digital oscilloscope at that time, but I went to Station B to watch the press conference of this Atomic oscilloscope (yes, Brother Atomic, the press conference lasted for half an hour... I was a little touched) . I am a person who doesn’t even watch Apple press conferences. I watched a cheap oscilloscope press conference for half an hour and was very moved. It said that three engineers, two analog experts and one embedded expert, worked for 18 months. Countless boards were made and the machine was made. It took 6 months to achieve a sampling rate of 250MHz using MCU+DAC. Awesome job. Although there is an Up master at Station B who sprays very well, I think this person doesn’t even read the instructions.

Always comparing things worth 50,000 yuan with things worth 500 yuan, they are very cheap.

In short, I admire such a plan for achieving such results, but I really can't say anything about some stupid designs. I can only say that their product managers are not good.

There are many specific disassemblies, you can check them out for yourself, I will also post them here.

HFD4/3-S ultra-small signal relay

Sometimes you can hear a clicking sound when changing gears, and it's caused by this thing.

When a certain value of current is passed into the coil, electromagnetic attraction is generated due to electromagnetic action or induction method, attracting the armature, and the armature drives the contact system, changing its state, thereby reflecting the status of the input current. The most basic working principle: the coil is energized → generates magnetic flux (armature, iron core) → generates attractive force → overcomes the armature resistance → the armature attracts the iron core → the armature drives the moving contact → the front contact is closed and the rear contact is opened.

(Relay sucks up) The current decreases → the attraction force decreases → the armature falls by gravity → the moving contact is disconnected from the front contact, and the rear contact is closed. (Relay falls) It can be seen that relays have switching characteristics and use the on and off circuits of their contacts to form various control indication circuits.

The specific use of the oscilloscope is very detailed in the instruction manual, but I wanted to write something that will help you get started quickly.

Remember these shortcut keys, it will be a lot more fun when viewing waveforms

This is probably what this interface looks like. The key is to look at the right side. You can also look at the lower left corner, but you need to use the measurement function to be precise.

Most of the time DC coupling is used

1. AC coupling: AC coupling removes the DC component through DC blocking capacitor coupling, and can only pass the AC component. 2. DC coupling: DC coupling pass-through, AC and DC pass through together, but the AC component is not removed. For oscilloscopes, waveform trigger sampling is a very important function, but this one is too cheap and only has upper and lower edge triggers, which I think is enough.

Triggering refers to setting certain trigger conditions according to requirements. When a certain waveform in the waveform stream meets this condition, the oscilloscope instantly captures the waveform and its adjacent parts and displays them on the screen. When a digital oscilloscope is working, regardless of whether the trigger is stable or not, it is always collecting waveforms. But only a stable trigger can have a stable display. The trigger system ensures that each time base scan or acquisition starts from the user-defined trigger condition, that is, each scan is synchronized with the acquisition, and the captured waveforms overlap, thereby stably displaying the waveform.

If it is automatic, the waveform will flash by. Because many times you don’t know what your waveform looks like, or even whether it exists, then you can use automatic capture. Then set the trigger rules. Here, we use a single sampling and catch it directly. Otherwise, the waveform will slip away instantly.

Note that X2-1 below is not the current signal width, but the length between the reference lines. You need to set the lines here.

This is to capture a set of waveforms

Can also be saved in built-in memory

Like this, post processing

The box I drew is the measurement area

I feel that this measurement function is quite useful.

Forget about anything else, I don’t need it.

Next, please ask the eldest brother to come out:

Damn, he has to be the eldest cousin

Look at what the teacher said. Are these human words? I'll catch a hand-cake seller in a while, and I won't be able to use an oscilloscope to take away all his eggs.

snort

Okay, I gave you the instructions.

The small button is for adjusting the brightness

More powerful measurement function, damn, love it

Give results with one click

Accurate fine-tuning of measurements is also possible

More delicate waveform output. This waveform is a bit outrageous. I don’t know what’s wrong.

This is the corresponding egg peak measurement result of the small oscilloscope above.

The following values ​​are the calculation results under different triggering methods.

Because there is a single capture, but I can't freeze the waveform.

When the green light turns on, you start sending signals. When you see something caught, press the switch:

That's it

But I'm a little confused, maybe because I haven't done enough research. I'm going to install a mechanical switch on my foot, and it will save a section when I step on it.

Because everyone is unwilling to use the oscilloscope, it is brainless for me to talk about one operation method alone. But the methods used are similar.