New Zoyi multimeter+oscilloscopes - ZT-70xS, up to 50MHz/250MSps (nov 2022)

[ajar171]

From the software standpoint, it is easy enough, although pretty annoying because of the constant beeping:
10 switch to voltage mode, it beeps
20 take a voltage measuerement
30 swith to current mode, it beeps
40 take a current measueremnt
50 goto 10

From the electrical standpoint, please someone check, a snippet from the chips manual is attached.

USB host mode for connecting external storage would be possible in software, but the ZT703 does not put out 5V to its USB port, so you would need a power supply for an external drive.
I think it is just not worth it, as you can store over a year of logging data with 1 log entry/minute and even with 3 log entries/second you get 55hours of logging time (assuming 15MB free space avaiable on the internal drive)
If that is not enough, there is always the possibility of replacing the SPI flash with a bigger one...

[LucSVK]

USB host mode for connecting external storage would be possible in software, but the ZT703 does not put out 5V to its USB port, so you would need a power supply for an external drive.
I think it is just not worth it, as you can store over a year of logging data with 1 log entry/minute and even with 3 log entries/second you get 55hours of logging time (assuming 15MB free space available on the internal drive)
If that is not enough, there is always the possibility of replacing the SPI flash with a bigger one...

Sure, the only issue is that flash in the CPU  can by simply overwritten too many times and can fail by time. After that you need to replace the CPU inside of the device. Isn't then better to use external storage whenever it's possible?

Wouldn't be possible just use small cheap USB hub and connect a power bank into it .. connect an external flash drive and this all would be connected into the DMM?
So you can log quite long time somewhere in the field??

[ajar171]

Sure, the only issue is that flash in the CPU  can by simply overwritten too many times and can fail by time. After that you need to replace the CPU inside of the device. Isn't then better to use external storage whenever it's possible?

Wouldn't be possible just use small cheap USB hub and connect a power bank into it .. connect an external flash drive and this all would be connected into the DMM?
So you can log quite long time somewhere in the field??

The flash inside the MCU is not used for data storage, it is way too small anyway.
The Zoyi has an onboard 16Mbyte SPI flash, wich is easy enough to replace if you wear it out (100.000 erase/write cycles are stated in the datasheet, so it should last for a long time)

Or you connect a laptop or a smartphone with USB, and log over the virtual com port, then you get virtually unlimited storage space.

[LucSVK]

Ah, they use "external" SPI flash. Ok, then it's better.
The concept with a powered USB HUB could be interesting (not sure if it could work),  but sure, it's not worth it.

[apollo11fan]

ajar171: could you fill us in on the progress you are making? I was really impressed by the replacement of the DMM function and the trace which you've indicated can be turned on/off. slick.

is your work available for download / install?
Are you allowing people to be beta-testers? If so, where do I sign up? 

[LucSVK]

ajar171: Do you have bigger schematic especially how is the circuit made around the COM plug?

I am looking at the schematic, but I don't see anything why it should be possible.
But I am just a beginner, so maybe somebody experienced will post his opinion.

Btw, is it possible somehow calibrate the ZT703S DMM ? Mine measures for example 13,14V instead of 13,10V. Not a lot, but still.
Mine looks like somebody sent it back before. So, maybe this is the reason.

Edit: It's 0,3%.
But I don't have a precise voltage source.

I took 2 different volt meter ( different models, different accuracy )
1 x Meterman 37XR  and 1 x Chauvin & Arnoux 5220G and measured the same source of voltage.
They measured exactly the same voltage 13,10V. ZT703S 13,14V

Or AC 232V measured as 236V by ZT703S

Thx

[Astur_TorQue]

Incredilbe job Ajar!

[ajar171]

ajar171: Do you have bigger schematic especially how is the circuit made around the COM plug?

Here you go, the poorly translated datasheet is attached (found in the internet). I have no idea, how to enter calibration mode with the stock firmware. I also did not try to enter it with my firmware (becuase of the isolator between the DMM chip and the MCU, I think it is not possible, but I could be wrong here).

Here is a way to do it:
http://www.kerrywong.com/2016/03/19/hacking-dtm0660l-based-multimeters/

With Kerry Wongs method, you can directly edit the cal factors in the eeprom, description of the eeprom data is in the attached datasheet. Be sure to make a backup!
I would not try it, without having a known good voltage source.

[ajar171]

Here is the content of the DMM eeprom from my meter (ZT703).

If someone would be so kind, and read the contents of the 24C02 of a ZT702 and post it here, maybe we could re-enable the temperature measurement in the ZT703.
Else I have to do it in software.

[indman]

If someone would be so kind, and read the contents of the 24C02 of a ZT702 and post it here, maybe we could re-enable the temperature measurement in the ZT703.

Here is a screenshot with ZT-702S

[ajar171]

This is strange.

According to the datasheet, the ZT703 should not have a continuity mode, but should have the temperature mode enabled, which is not the case.
The ZT702 should have and has both modes.

I have the feeling, that the DMM chip has a custom firmware for Zoyi and does not care about the enabled/disabled features in the eeprom.
Anyway, I will try to change the eeprom of the 703 to the 702 settings (adress range 0x80 to 0xBF) later and see what happens.

[indman]

I have the feeling, that the DMM chip has a custom firmware for Zoyi and does not care about the enabled/disabled features in the eeprom.

You think correctly, very often the operating modes are already programmed in the main DMM chip.

[ajar171]

I have the feeling, that the DMM chip has a custom firmware for Zoyi and does not care about the enabled/disabled features in the eeprom.

You think correctly, very often the operating modes are already programmed in the main DMM chip.

Then I will save myself the trouble of reprogramming the eeprom, and go the software route for the temperature measurement.
It is a basic voltage to temperature conversion with a lookup table anyway, not that big deal in software (there is probably working and tested open source code on github already...)

[ajar171]

ajar171: could you fill us in on the progress you are making? I was really impressed by the replacement of the DMM function and the trace which you've indicated can be turned on/off. slick.

is your work available for download / install?
Are you allowing people to be beta-testers? If so, where do I sign up? 

I am working on getting FatFs and USB mass storage working again (I had to change how the SPI flash sector caching works, which broke FatFs and USB-MSC).
Then I have to make a menu framework for the new functions, because the meter is currently controlled over the serial connection (I am too lazy to use the buttons ), core DMM functions are done and working.
When DMM mode (including the new functions) is ready, than we can start beta testing

My warning again:
- there is no going back to stock firmware
- the firmware is being made on the PCB version 2.2, and I don't know if it works on other revisions, because I only have this meter. In the review video of Dave the version 1.8 can be clearly seen. I don't know, what they have changed
- as always, absolutely no warranty

[eljjc]

I have the feeling, that the DMM chip has a custom firmware for Zoyi and does not care about the enabled/disabled features in the eeprom.

You think correctly, very often the operating modes are already programmed in the main DMM chip.

Then I will save myself the trouble of reprogramming the eeprom, and go the software route for the temperature measurement.
It is a basic voltage to temperature conversion with a lookup table anyway, not that big deal in software (there is probably working and tested open source code on github already...)

Isn't an internal temperature sensor needed to be able to calculate the temperature based on the voltage of a thermocouple?

[ajar171]

Isn't an internal temperature sensor needed to be able to calculate the temperature based on the voltage of a thermocouple?

For thermocouples, yes. For PT100 or PT1000 no.

The main MCU has an internal temperature sensor, which could be used for cold junction compensation.
This will introduce an error, because the MCU is physically far away from the cold junction (the terminals) and it is also heating itself up, so I think a user compensation temperature input will be required.

PT sensors are easy enough to implement, so I will save the thermocouple stuff for later

[eljjc]

Yes, I understand. Thank you for your response, and congratulations on your amazing initiative!

[Edmiri]

Any update on the firmware? Plz post any video. This stuf is so exiting. 

[sergkz]

So, did the Chinese abandon the ZT703? They're probably making a 704 super full HD 1 GHz out of crap and sticks

[lchao]

Did domeone have a chance to test the v1.49 FW?
https://zotektools.com/products/triple-in-one-instrument-combining-oscilloscope-multimeter-and-signal-source/ -> Click on the green "Russian version firmvare" button

[xKertx]

That's odd. Why make country specific firmware when current firmware already has menu option to change language (english/chinese). Why not just add additional languages to the existing menu.

[csuhi17]

Did domeone have a chance to test the v1.49 FW?
https://zotektools.com/products/triple-in-one-instrument-combining-oscilloscope-multimeter-and-signal-source/ -> Click on the green "Russian version firmvare" button

i just update but doesn't tested.
language : English/China/Russian.

Not much improvement.
In the 100ms/Div timebase, if I apply a few Hz wave to one of the inputs, there will be an anomaly in the wave.
AUTO still doesn't work well.

[chebo]

And I recently bought an old (but unused) Rigol 1052E and now I have no questions or misunderstandings, as was always the case with this ZOYI... )))

[indman]

And I recently bought an old (but unused) Rigol 1052E and now I have no questions or misunderstandings, as was always the case with this ZOYI... )))

It's the right decision on your part! Toys for kids. Grown-ups need devices they can trust, not toys.

[csuhi17]

And I recently bought an old (but unused) Rigol 1052E and now I have no questions or misunderstandings, as was always the case with this ZOYI... )))

It's the right decision on your part! Toys for kids. Grown-ups need devices they can trust, not toys.

Please don't insult others, a grown man with three children, two wives and four mistresses has the right to buy and play with toys!