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

[Heyrst]

Instead of a recall, it would be enough if they supplied 4.3V charging voltage cells. Example SANYO UR18650ZTA or LG ICR18650 E1

[tol]

I confirm the issue.
Charger NO BATTERY = 4.46V
Charger WITH BATTERY and the LED is flashing = 4.33V
Charger WITH BATTERY before turn off = 4.30V with several short peaks up to 4.50V during final 5-10 seconds, then turn off. The battery keeps 4.28V voltage that slowly reduces.

However, the battery is cold, it's just 1 degree Celsius higher than the environmental temperature (the device was open during the test and the battery was not discharged before the test, so it did not charge long). I don't think it will burn unless you change it with something that has no internal overcharge protection. Maybe it's a good idea to stop charging it at ~80% manually to prolong the battery life, but I understand that it is not convenient.

My guess is that it's not a design mistake. Most likely it's a marketing trick just to say in the reviews that their device works longer than the devices of the competitors, and no matter that the battery will die faster. The choice was made, the money was paid, that's the only thing that is important in the modern marketing

Besides, the trigger issues are not fixed in the latest firmware and I'm tired of waiting when they fix them. I've already started to look for another inexpensive multi-meter with tested firmware. ZEEWEII DSO2512G seems to have many good reviews, but some users noted that they probably changed some parts to cheaper ones in the last 1-2 years, and the modern devices have more noise than the devices that were initially produced under the same name. This is also a rather typical and disgusting Chinese marketing trick to sell absolutely different and cheaper hardware in the case and under the name of the hardware that was proved to be good some time ago.

[MLXXXp]

I don't know why nobody mentioned it in this thread yet, but Zoyi used the wrong charge controller ME4086B which has charge termination at 4.35V.

Since this thread is also for the ZT-702S, it should be noted that the ZT-702S uses a TP4056 charge controller (or equivalent), specified for 4.2V. On mine, I measured 4.185V on the battery terminals without the battery installed. So, the ZT-702S doesn't have this problem and is safe for charging the cell provided with it.

[Heyrst]

Has the ZT-703S model shematic been clarified to see if there is any sensible point where the HC-05/HC-06 bluetooth serial circuit would be activated when the uart is turned on.

Previously added the HC-05/HC-06 bluetooth circuit to the multimeters so that the bluetooth circuit power is activated when a signal comes to the uart. The connection is unnecessarily complicated. When I don't want the bluetooth to always be on when the meter or backlight is on.

[redlopa]

Here is a fix for this problem. It’s not my video- but I have a unit with the same problem, which is dry joints on the chip under the on/off button.

https://youtu.be/P6QntvNAdx8

[jjarvi]

Nevermind, it's 3V. There are two similar regulators on the board next to the signal generator output.
Could someone check the supply voltage for the DMM chip?

I also have one of these with a faulty DMM mode. The DMM chip supply rail on this one is only ~0,4 volts and the voltage regulator is running really hot. It's the SOT-23-5 right next to the battery holder on the right side.

I think the regulator is from Microne. It has a "wave" logo and marking P8XC on top of it, but I'm unable to deduce which one it is from that.

[tol]

Maybe someone already wrote simple software to parse the 703 terminal output to something like:
date_time,value
date_time,value
date_time,value
...
It would be great to have it for Linux, but Win is also ok. I want to log the process to see how quickly my super-capacitors discharge and I thought this Zoyi could be used as a logger if there is some kind of software that can write such logs.

[Kris0725pl]

We made application working with PC for zoyi...
It is also option log to file...but with no date time...i think it is easy add.

[tol]

I've been cooperating with ChatGPT and it helped me a lot to write the following script Not from the first attempt, but finally it works:

Code: [Select]

#!/bin/bash

stty -F /dev/ttyUSB0 115200 cs8 -cstopb -parenb

LOG_FILE="zoyi_data.csv"
buffer=""

while IFS= read -r -n1 char; do
     if [[ "$char" == " " ]]; then
        if [[ -n "$buffer" ]]; then
            if [[ "$buffer" == *:* ]]; then
                key="${buffer%%:*}"
                value="${buffer#*:}"
                #timestamp=$(date +"%Y-%m-%dT%H:%M:%S")  #ISO
                #timestamp=$(date +%s); # linux timestamp
                timestamp=$(date +"%Y-%m-%d %H:%M:%S")
                output="$timestamp,$key,$value"
                echo "$output"
                echo "$output" >> "$LOG_FILE"
            fi
            buffer=""
        fi
    else
        buffer+="$char"
    fi
done < /dev/ttyUSB0
The output is a CSV file, you can build graphs in Excel-like spreadsheet software. Date/time format can be changed as you like (edit  "timestamp=").
Output example (works not only with voltage but with other modes too):

Code: [Select]

2025-09-07 12:10:07,VVoltage,04.668
2025-09-07 12:10:07,VVoltage,04.667
2025-09-07 12:10:07,VVoltage,04.664
2025-09-07 12:10:08,VVoltage,04.663
2025-09-07 12:10:08,VVoltage,04.662
2025-09-07 12:10:08,VVoltage,04.661
2025-09-07 12:10:09,VVoltage,04.661
2025-09-07 12:10:09,VVoltage,04.660
2025-09-07 12:10:09,VVoltage,04.660
2025-09-07 12:10:10,VVoltage,04.660
2025-09-07 12:10:10,VVoltage,04.659
2025-09-07 12:10:10,VVoltage,04.658
2025-09-07 12:10:11,VVoltage,04.657
2025-09-07 12:10:11,VVoltage,04.658
2025-09-07 12:10:11,VVoltage,04.657
2025-09-07 12:10:12,VVoltage,04.657
2025-09-07 12:10:12,VVoltage,04.656
2025-09-07 12:10:12,VVoltage,04.656
2025-09-07 12:10:13,VVoltage,04.655
2025-09-07 12:10:13,VVoltage,04.654
2025-09-07 12:10:13,VVoltage,04.654
2025-09-07 12:10:14,VVoltage,04.653
2025-09-07 12:10:14,VVoltage,04.653
2025-09-07 12:10:14,VVoltage,04.652
2025-09-07 12:10:14,VVoltage,04.652
2025-09-07 12:10:15,VVoltage,04.652
2025-09-07 12:10:15,VVoltage,04.651
2025-09-07 12:10:15,VVoltage,04.651
2025-09-07 12:10:16,VVoltage,04.651
2025-09-07 12:10:16,VVoltage,04.650
2025-09-07 12:10:16,VVoltage,04.650
2025-09-07 12:10:17,VVoltage,04.649
2025-09-07 12:10:17,VVoltage,04.649
2025-09-07 12:10:17,VVoltage,04.649
2025-09-07 12:10:18,VVoltage,04.648
2025-09-07 12:10:18,VVoltage,04.648
2025-09-07 12:10:18,VVoltage,04.648
2025-09-07 12:10:19,VVoltage,04.647
2025-09-07 12:10:19,VVoltage,04.646
2025-09-07 12:10:19,VVoltage,04.646
2025-09-07 12:10:20,VVoltage,04.646
2025-09-07 12:10:20,VVoltage,04.645
2025-09-07 12:10:20,VVoltage,04.646
2025-09-07 12:10:21,VVoltage,04.645
2025-09-07 12:10:21,VVoltage,04.645

[FixyMixy]

On firmware V157 on my device the waveform jumps a lot immediately after the trigger point on frequencies above ~30MHz.
Is it a known bug?
I flashed V149 and now it's OK!

[yanko.pt]

I can't seem to find V149 anywhere 

Do you mind uploading it somewhere or sending it over? Thanks!

[OLderDan]

On firmware V157 on my device the waveform jumps a lot immediately after the trigger point on frequencies above ~30MHz.
Is it a known bug?
I flashed V149 and now it's OK!

Did you switch modes to high speed?

[Allleeexxx]

Hello, If someone need I have 9 extra 4086A in Romania.

[FixyMixy]

I can't seem to find V149 anywhere 

Do you mind uploading it somewhere or sending it over? Thanks!

It's NOT my link, but you have it: https://drive.google.com/file/d/1aaglR_qXuagTngzffufRUz1cbYptBq_K/view

[FixyMixy]

Did you switch modes to high speed?

Yes, I did.
On V149 it's able to display up to 70MHz, but I found some bugs with measurements display
Rise time is 6.6 ns in high and 10 ns in normal mode.


Does anyone have V156 or V155? Please, share it here!

[tol]

156 as requested

[FixyMixy]

Firmware V156 is all good.
But the V157 gives a wobbly signal after trigger point.

It's the same 50MHz signal in "high" sampling mode on the pictures.
All except the first pic are from the V157.

[FixyMixy]

Is it a common behavior, or it's my faulty unit?

[OLderDan]

Is it a common behavior, or it's my faulty unit?

I can't say, without access to a 50mhz signal, but I hope not!

[csuhi17]

Is it a common behavior, or it's my faulty unit?

In normal mode the signal look AM modulated with firmware 1.56
In high mode too but to a much lesser extent, the bottom of the waveform wobbles 3/4 division and the top 1/4 division.
With firmware 1.57 it's like yours, rubbish.

[FixyMixy]

Is it a common behavior, or it's my faulty unit?

In normal mode the signal look AM modulated with firmware 1.56
In high mode too but to a much lesser extent, the bottom of the waveform wobbles 3/4 division and the top 1/4 division.
With firmware 1.57 it's like yours, rubbish.

Thank you! I'm getting AM-like effect too. But it's fine when the frequency is reaching the Nyquist frequency limit (on primitive trigger and interpolation systems).

So the firmware V157 has a bug that leads to waveform distortions at high frequencies.
(Sorry for overemphasizing. I hope someone from zoyi will read this thread....)

PS: V156 is available here few posts up.

[csuhi17]

I don't think it's likely that they'll read it.
So far I've seen a few genuine comments and posts from Siglent, and from one of the Fnrisi scope makers.

If you want to be sure, report it to them directly.

[FixyMixy]

I've sent them this info, let's see what will happen... 

[indman]

FixyMixy, https://www.eevblog.com/forum/testgear/new-zoyi-multimeteroscilloscopes-zt-70xs-up-to-50mhz250msps-(nov-2022)/msg5899762/#msg5899762
https://www.eevblog.com/forum/testgear/new-zoyi-multimeteroscilloscopes-zt-70xs-up-to-50mhz250msps-(nov-2022)/msg5899778/#msg5899778
https://www.eevblog.com/forum/testgear/new-zoyi-multimeteroscilloscopes-zt-70xs-up-to-50mhz250msps-(nov-2022)/msg5874902/#msg5874902 

[tol]

FixyMixy

Slowly, but they change things, but also add new bugs at the same time. My guess is that the device was initially developed by another team that left the company for some reason. The new team of programmers doesn't know how it works and moves slowly by the "method of tries and errors". This is typical for small Chinese companies. I've got a light quality meter Opple light master IV, it has the same issue - the Opple light master III was good, but the developers left the company. The new team released Opple light master IV and it works much worse than the previous version, because the new team doesn't understand completely how the initial code works, they stated it in various forums! Now the development of  the light master IV is completely abandoned, although it looked really promising at the beginning. I hope Zoyi will not abandon 703 firmware development, but it really feels that they are not really interested in developing it There appeared a lot of newer pocket oscilloscopes with better specs recently, maybe they just understand that their device is not competitive anymore. Although I think it could be a great device for it's price if the firmware is made reliable, but look, the price for it dropped twice during the last year, it feels like they just want to get rid of its stock while people are still willing to buy it.