Portable Oscilloscopes List (cheap)

[tigrou]

This is more a hobby project than a real usable thing.

The Arduino ADC only works up to ~12.5kHz so usable bandwidth can't be more than about 5kHz. 

Well it's actually way worse than this.
I created a simple Arduino program that just read the ADC and send it via serial.
Using a python script I read data from the COM port and calculated reads per sec. The best I could get is about 2400 captures per second.
It's clearly the serial communication which is limiting factor, it can go up to 7000 reads/sec without it.

When you think about it, it make sense. 115200 bauds / 8 bits / 4 (the average amount of bytes transferred per read) = 3600 / sec (theoretical best)
There is probably tricks to make this even faster (bypassing analog read and using interrupts), here is an example : https://forum.arduino.cc/t/what-effect-arduino-analogread-speed/978360/15

Have you considered the Rigol DHO804? It may be slightly out of budget, but as it's PD compatible you can use any decent power bank and then have a "proper" portable oscilloscope. They often go on sale for less than the usual price

https://www.lambdaphoto.co.uk/rigol-dho804-70mhz-bw-12-bit-4-channel-high-definition-oscilloscope.html#specifications
https://www.lambdaphoto.co.uk/pdfs/Rigol/LAMBDA_DHO8000_Datasheet.pdf

You have to define "cheap" and "portable". That one will definitely not fit in your pocket.
Other than that it seems to be a really nice scope for anyone looking for a small form factor. But it's clearly not a pocket one.

[Fungus]

When you think about it, it make sense. 115200 bauds / 8 bits / 4 (the average amount of bytes transferred per read)

4 bytes per reading?

It's a 10 bit number, 4 bytes is 32 bits - enough to transfer 3 readings.

You can make the serial port faster than that, too.

[tigrou]

When you think about it, it make sense. 115200 bauds / 8 bits / 4 (the average amount of bytes transferred per read)

4 bytes per reading?

It's a 10 bit number, 4 bytes is 32 bits - enough to transfer 3 readings.

You can make the serial port faster than that, too.

Isn't Serial.println() converting everything into characters ?

[Fungus]

Isn't Serial.println() converting everything into characters ?

Yes. ASCII text plus a newline - a huge waste just to transmit 10 bits of data.

[ledtester]

Isn't Serial.println() converting everything into characters ?

Use Serial.write() to send bytes, e.g.:

https://arduino.stackexchange.com/questions/66300/using-serial-write-to-send-a-uint32-t-send-one-byte-x4-or-send-4-bytes-x1

[tigrou]

Isn't Serial.println() converting everything into characters ?

Use Serial.write() to send bytes, e.g.:

https://arduino.stackexchange.com/questions/66300/using-serial-write-to-send-a-uint32-t-send-one-byte-x4-or-send-4-bytes-x1

It's just me being stupid. I wanted to post about that but you guys were faster than me. I expected the Arduino API to be so "entry level" that I don't even think about possibility to have a method for writing something else than a string.

This probably can make serial sending 2 or 3 times faster. I have to try it again.

EDIT:
With Serial.write(int) (2 bytes per write) I got 4464 writes/sec. I expected something higher. I removed the analogRead() from the loop (thus only doing writes) and it's still the same.
Even with start, stop and parity bits, I got 16+3 = 19 : 115200 / 19 = 6063 ops/sec

I tried to send 200 bytes at once and got 59 writes/sec (which mean 11800 bytes per sec). It's close to the theoretical 115200 bauds / 8 = 14400 bytes per sec.
So maybe one way would be to buffer ADC reads and then send it once.

[ledtester]

Try this code:

https://chisight.wordpress.com/2016/03/25/speeding-up-the-adc-on-an-arduino-atmega-328p/

[Kean]

EDIT:
With Serial.write(int) (2 bytes per write) I got 4464 writes/sec. I expected something higher. I removed the analogRead() from the loop (thus only doing writes) and it's still the same.
Even with start, stop and parity bits, I got 16+3 = 19 : 115200 / 19 = 6063 ops/sec

I tried to send 200 bytes at once and got 59 writes/sec (which mean 11800 bytes per sec). It's close to the theoretical 115200 bauds / 8 = 14400 bytes per sec.
So maybe one way would be to buffer ADC reads and then send it once.

The async comms will be your limiting factor.  FYI, with 8N1 comms, there are always 10 bit times per byte, so absolute max will be 11520 bytes per sec ... which you can reach only if you can avoid any inter-character delays by keeping the transmit buffers full.  You hit this by doing those bulk writes.

Async transfers will continue in the background* while you do your next ADC conversion, so I don't think speeding up the ADC will help.
(* until the buffer is full and there is a pause, which will screw up your inter-measurement timing a bit)

You need to speed up the comms link, e.g. a either higher baud rate or native USB.

[Fungus]

Arduinos can transmit more than 115200 baud.

In practice the capacitance of the sample and hold circuitry of the ADC limits the Arduino to about 12k samples/sec.

(You can set the ADC's clock speed higher than that but you won't get useful data)

12k samples @ 10 bits can be sent at 230400 baud.

[Fungus]

12k samples @ 10 bits can be sent at 230400 baud.

OTOH: Any PC sound card will completely destroy that performance and you can use the Digilent Waveforms software with it. 

[tigrou]

12k samples @ 10 bits can be sent at 230400 baud.

OTOH: Any PC sound card will completely destroy that performance and you can use the Digilent Waveforms software with it. 

I read about PC soundcard sometimes ago they have some DC filters (at least one the mic) that make somewhat unusable for anything else than AC signals

Digilent Waveforms : is this official ?

[ledtester]

Digilent Waveforms : is this official ?

Yes - it's the same software you would use with the Analog Discovery.

A blog post about it with some tips for interfacing with real-world signals:

https://www.nutsvolts.com/magazine/article/turn-your-computers-sound-card-into-a-scope

Can be used with "internal" sound cards as well as USB sound cards.

[tigrou]

Digilent Waveforms : is this official ?

Yes - it's the same software you would use with the Analog Discovery.

A blog post about it with some tips for interfacing with real-world signals:

https://www.nutsvolts.com/magazine/article/turn-your-computers-sound-card-into-a-scope

Can be used with "internal" sound cards as well as USB sound cards.

Thanks, but the link to download the software is dead : https://analogdiscovery.com/download

From the article, that's the typical response to expect from a soundcard (as expected) :


Probably better than some cheap oscilloscope on some points (sensivity) but worse on some others (forget about any DC measurements).

[tunk]

New pocket scope, Holdpeak HP-500K

- bandwidth 500kHz, 2.5MSps
- 10mV/Div - 10V/Div (1-2-5 Step)
- 10μs/Div - 50s/Div (1-2-5 Step)
- 2.8-inch LCD, 320x240
- 400mAh, 3h runtime
- 103x73x25mm, 100g
- price on aliexpress US$40:
https://www.aliexpress.com/item/1005008776106526.html

https://holdpeak-store.com/holdpeak-hp-500k-mini-oscilloscope-portable-handheld-tablet-oscilloscope-with-500khz-2-5ms-s-sampling-rate-2-8-screen/

[tunk]

New small scope, BSIDE OT3, 1ch, 10MHz/48MSps

- 20mV/div - 10V/div
- 100ns/div - 20s/div
- 3.2" screen, 320x240
- 128x63x22mm, 166g
- US$30-35 on aliexpress

[aviphysics]

• Zeeweii DSO3D12
• DreamSourceLab DS Touch DS4T252
• ...........

Are these still the two scopes to look at? I'm also looking at around the $150 range in the USA, but would be happy to go under that number.

My main use case is for diagnosing problems in RC planes and quad copters.
* This is mostly for looking at Serial UART, i2C, or SPI signals, so I don't need super high bandwidth.
* Most important thing is being easy & fast to pull out and setup for a measurement.
* I also don't care too much about precision, as long as I can see if the trace looks relatively clean and well formed.
* Digital phosphor would be nice to have.

I currently have a Rigol DS1054Z, but it spends most of its time under my desk and always feels inconvenient to setup. More convenient than my old analog scope, but still inconvenient.

[Twiggy]

I'm interested in DS4T252 or DS03D12 too. As I would use it around the garage I would like to know how those would fare if dropped 1 meter (I can see myself knocking it down from the engine bay)