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

[nikbry]

Thank you everyone for the help and suggestions.
I did find a bit of time today to do a bit more testing.

I have come to the conclusion that the problem is with my new signal generator (if you can call it that) the (in)famous Feeltech FY3200S. The Vpp output specially on the sine wave seems to drop starting at  1kHz reaching 4.6Vpp (5Vpp setting) at 100kHz, but that's an issue to be dealt with in another thread.
When comparing the Zoyi and the Owon VDS1022i the differences were insignificant, also the Vrms measurements with a multimeter confirmed the voltage drop, all that made me suspect the signal generator.  But the Zoyi definitely doesn't like the Owon probes, need to spend some more time investigating that.

Combine my ignorance and incompetence with three cheap untrustworthy pieces of equipment and the level of uncertainty of what's going on tends to infinity.
I wish I could justify buying "real" equipment.


Thanks for doing some tests for me and all the help and tips of using cursors instead of eyeballing and switching timebases, etc.
Sorry, for posting before doing some more thorough testing.

[Obi-Wan]

The multimeter chip resembles the well-studied DTM0660. That's why I simply saved the contents of the soldered-in I2C EEPROM. The address 0x2A contains the calibration coefficient for current with a limit of 2.5A. By changing it I adjusted the readings.

BTW, are you sure, that 703S has DTM0660? Because now I am reading, that the previous 702S had DM1109EN, and not DTM0660. The chip on 703S is unfortunately lasered out. Did you correct the coeficcients on the 703S itself?

[xKertx]

I'll try to check in the next few days with all the probes I have. What frequencies are you interested in?

The 1khz test signal.
See post #604.

[m72]

BTW, are you sure, that 703S has DTM0660? Because now I am reading, that the previous 702S had DM1109EN, and not DTM0660. The chip on 703S is unfortunately lasered out. Did you correct the coeficcients on the 703S itself?

I don't know what chip is used in the multimeter. It's definitely not DTM0660 since it can show 25,000 counts.
However, the data structure in EEPROM is similar.
The first thing I tried was changing the 16-bit value in the cell at address 0x2A and it worked.
The dump looks very similar to DTM0660, but since it works in tandem with the main controller, I didn't touch anything else.

[csuhi17]

again, the common opinion is DTM0600 and DM1106EN are cheap clones of Hycon HY12P66, that's why there are so cheap DMMs with them compared to the one that has original Hycon HY12P66 inside.

I don't think DTM0660L/DM1106EN are clones. You can see from the DTM0660L photo



there are two logos on the chip, DreamTech / HyconTek.





Dream Tech International Ltd is just a trading company import the chips from Taiwan, and export the chips to the manufacturers in China. They do not produce any semiconductors.

HyconTek is just provided a DMM solution to the customers. You can order your customized chips from them.

Dream Tech International Ltd
http://www.dreamtechintl.com.cn/en/about/about-108.html

So isn't it?

[Edmiri]

Even  1.38 has a bug.

[Obi-Wan]

The multimeter chip resembles the well-studied DTM0660. That's why I simply saved the contents of the soldered-in I2C EEPROM. The address 0x2A contains the calibration coefficient for current with a limit of 2.5A. By changing it I adjusted the readings.

I did it! But it was not 0x2A, but 0x2E - 0x2F (Little Endian encoded) for 0-2,5A range, and 0x54 - 0x55 for 2,5 and above range.

[IC_Toaster]

I have detected what I think is a bug.
Using the signal generator I see that the amplitude changes when the frequency changes from 995Hz to 1KHz for senoidal and square waves as can be seen in the attached images.

[Altair8800]

 :'(  Ok, I just flashed my ZT-703S with newer firmware version 1.3.9

but when it was done it might have BRICKED the unit.

Right now, all it is doing is turning on and off the ZOYI logo and that is it.  It will not let me in multimeter or oscilloscope mode.  It will not let me even power off the device (even long pressed the Power button for say 20 seconds) no go.  I've tried disconnecting the battery, but when reconnecting it will only turn on and off the ZOYI logo.  It will not let me go to USB mode so I can reflash it with and older version.

Any suggestions on how to fix this?  Like are there any special keys you need to press to get out of this and/or get back to the USB mode so I can reflash the unit. 

Thanks.

[RAPo]

Doin't worry, I have it every time I flash a new firmware.
Do this.

:'(  Ok, I just flashed my ZT-703S with newer firmware version 1.3.9

but when it was done it might have BRICKED the unit.

Right now, all it is doing is turning on and off the ZOYI logo and that is it.  It will not let me in multimeter or oscilloscope mode.  It will not let me even power off the device (even long pressed the Power button for say 20 seconds) no go.  I've tried disconnecting the battery, but when reconnecting it will only turn on and off the ZOYI logo.  It will not let me go to USB mode so I can reflash it with and older version.

Any suggestions on how to fix this?  Like are there any special keys you need to press to get out of this and/or get back to the USB mode so I can reflash the unit. 

Thanks.

[Altair8800]

BIG THANKS to RAPo,

That was a scare...  Thought I bricked my unit...

I believe the recovery steps are

• Remove Battery (by taking off back case)
• Wait for a minute
• Plug in USB cable (while battery is removed)
• Press (maybe have to hold few seconds) F1 Key
  This should put you into USB Mode which should allow you to see the ZT-703S as a Drive
  
• Go to the Firmware folder and copy the firmware from your computer hard drive to this firmware folder
  Should see prompt on ZT-703 uploading the firmware
• After a while new firmware should be updated on ZT-703S
• I then powered off, reinstalled the battery, and put back the DDM back cover.

[Obi-Wan]

:'(  Ok, I just flashed my ZT-703S with newer firmware version 1.3.9

but when it was done it might have BRICKED the unit.

Right now, all it is doing is turning on and off the ZOYI logo and that is it.  It will not let me in multimeter or oscilloscope mode.  It will not let me even power off the device (even long pressed the Power button for say 20 seconds) no go.  I've tried disconnecting the battery, but when reconnecting it will only turn on and off the ZOYI logo.  It will not let me go to USB mode so I can reflash it with and older version.

Any suggestions on how to fix this?  Like are there any special keys you need to press to get out of this and/or get back to the USB mode so I can reflash the unit. 

Thanks.

Why did you choose 1.3.9 and not the latest 1.4.2?

[IC_Toaster]

The oscilloscope doesn't work right.
This is the signal generated and measured by Zoyi:



And this is the signal measured by a Siglent oscilloscope:



It is suppose than the signal amplitude is 2.5 Vpp but Zoyi measures just 2.3 Vpp, and Siglent measures 2.5 Vpp. My firmware is 1.4.2
I trust the Siglent oscilloscope.

Has someone notice any amplitude measurement error?

[matefon]

The built in signal generator is considered to be 'useless' or 'toy' by some testers. I don't own a signal generator (I don't need one for now), so the only use of the internal one was to calibrate the scope probes.
If you have a signal generator try comparing the ZT703s with the Siglent scope. I don't know for sure, but the internal electronics of the Zoyi may interfere with the scope when probing the internal generator?

[IC_Toaster]

The built in signal generator is considered to be 'useless' or 'toy' by some testers. I don't own a signal generator (I don't need one for now), so the only use of the internal one was to calibrate the scope probes.
If you have a signal generator try comparing the ZT703s with the Siglent scope. I don't know for sure, but the internal electronics of the Zoyi may interfere with the scope when probing the internal generator?

The signal seems a little noisy.
I don't have any signal generator either, but maybe you are right and the problem is that I am measuring with the same device which is generating the signal and there may be any kind of interference

[csuhi17]

I quickly tested my copy.
When I used its own generator, it was 2.4Vpp.
changing the time base also changes the measured value.
It measured 2.5Vpp in 200us/div.

I noticed that the accuracy of the measurement also depends on the time base, Zoyi can't always determine the voltage of the signal very well.
Sometimes it needs more samples.
This is a bug or a hardware limitation.

Using an external generator, the frequency was stable, and the voltage measured a fixed 2.5Vpp.

When you use the "signal generator" in oscilloscope mode, the properties of the oscilloscope deteriorate. It is no accident that it limits the minimum time base to 100us/Div.

If you have the opportunity, make a simple electronics that you can measure with your Siglent and Zoyi.

[IC_Toaster]

I quickly tested my copy.
When I used its own generator, it was 2.4Vpp.
changing the time base also changes the measured value.
It measured 2.5Vpp in 200us/div.

I noticed that the accuracy of the measurement also depends on the time base, Zoyi can't always determine the voltage of the signal very well.
Sometimes it needs more samples.
This is a bug or a hardware limitation.

Using an external generator, the frequency was stable, and the voltage measured a fixed 2.5Vpp.

When you use the "signal generator" in oscilloscope mode, the properties of the oscilloscope deteriorate. It is no accident that it limits the minimum time base to 100us/Div.

If you have the opportunity, make a simple electronics that you can measure with your Siglent and Zoyi.

I have measured a Vcd voltage. It was supposed to be a 5 Vdc.








The value obtained with the multimeter is right, but the values obtained with the oscilloscope are wrong, and the RMS value is the worst..

[nikbry]

I have measured a Vcd voltage. It was supposed to be a 5 Vdc.


The value obtained with the multimeter is right, but the values obtained with the oscilloscope are wrong, and the RMS value is the worst..

The voltage measurements are not reliable, it's always better to use the cursors.
Could you please check if using the probe at 1x makes any difference?

[IC_Toaster]

I have measured a Vcd voltage. It was supposed to be a 5 Vdc.


The value obtained with the multimeter is right, but the values obtained with the oscilloscope are wrong, and the RMS value is the worst..

The voltage measurements are not reliable, it's always better to use the cursors.
Could you please check if using the probe at 1x makes any difference?

The probe was at 1x.
I didn't use the cursors, but the shown signal has the same amplitude than the values measured.
Anyway, I will do it again using the cursors.

[nikbry]

The probe was at 1x.
I didn't use the cursors, but the shown signal has the same amplitude than the values measured.
Anyway, I will do it again using the cursors.

I meant using the cursors when analyzing periodic signals, with a DC signal it can be eyeballed easily.
My scope/probe combo is accurate in 1x up to 6MHz. In 10x mode I do have attenuation starting at 100kHz. If I calibrate the probe I can either adjust to minimize distortion or attenuation, but there's really no sweet spot, so I have to compromise.

[apollo11fan]

Hello - does anyone know if Zoyi is working on an update to firmware 1.4.2 and if so, when we might expect it? Thanks.

[nikbry]

Trying to understand the nature of the attenuation of the Zoyi I measured a 5Vpp sinewave from a signal generator using the Zoyi probe both on the Zoyi and the OWON VDS1022i. I measured in orders of magnitude from 1kHz up to 10MHz. The Owon measures approx 5Vpp through the entire range, the Zoyi does not.
These are the results:

[Grandchuck]

Hello nikbry.  I repeated your measurements and got 5 volts up to 1 MHz where it dropped to 4.9 and then at 10 MHz I got 4.7.

[nikbry]

Hello nikbry.  I repeated your measurements and got 5 volts up to 1 MHz where it dropped to 4.9 and then at 10 MHz I got 4.7.

Thanks for taking the time. Is your probe perfectly compensated?
As I said before my unit is extremely sensitive to the slightest variation in compensation of the probe. If I remove the distortion completely (perfect squares) then I get the attenuation shown in my screenshots. If I overcompensate the probe then I get results similar to yours.

[Grandchuck]

The probe is properly compensated.