Test/Review of YZXStudio USB meter ZY1270

YZXStudio USB meter ZY1270

Official specifications:

  • Input voltage: DC 3.5V-24V

  • Input current: ± 3A

  • Voltage resolution: 0.0001V (0.1mV)

  • Current resolution: 0.0001A

  • Cumulative capacity: 0-99999Ah; 0-99999Wh

  • Capacity resolution: 0.0001Ah; 0.0001Wh

  • Accuracy: Voltage 0.1+2d; Current 0.2+2d; Ah capacity 0.5; Wh capacity 0.5

  • Display: 1” 128x64 pixel LCD with backlight

  • Update rate: Every 0.36s

  • Idle current consumption: ~11mA/6mA (with backlight on/off)

  • Current shunt resistance: 10mOhm

  • Overall circuit resistive loss: ~42mOhm (including contact resistance on USB connectors)

  • Memory: FRAM, good for 10 billion write cycles

  • Memory operation mode: write on every update in cumulative capacity + load balancing technique

I got it from ebay dealer dz-stuido.

YZXStudio makes a series of usb meters with nearly identical specifications, there is also frequent software update with significant improvements. It is possible to install update, but it requires special tools and access to the updated software.

This table compares some of the YZXStudio usb meters.

How does it look

I got it in a small metal box with a Chinese (I assume) manual, because the user interface is basically the same as all other YZXStudio meters I did not have any problems using it.

Notice the small button, it is used for all the functions. There is also a micro usb input connector.

The top usb connector has local auto coding, i.e. when using this the power coding on the power supply is ignored.
The bottom usb connector has data connection from the input connector, any usb voltage shown on the display is for this connector and the usb input connectors.

Welcome screen, it is shown when power is applied (it can be disabled).

The first screen, it shows V, A, Ah and Wh, the “0” is selected memory bank.
It do also have space for the MCU temperature.

Next screen shows W and ohm, instead of Ah and Wh.

This screen is used to calculate cable resistance, to use it a constant current load is required.
First do a measure without the cable, hold down the button to set the reference. Then add the cable between the usb power source and the usb meter. The display will show the resistance.

This screen shows usb coding and voltage. The time has been moved to this screen. It also shows the trickle current threshold, only current above this value is summed (Value is configurable). The temperature is the internal MCU temperature.
Note: Sometimes the display will show two usb codings, because it cannot determine which one is valid.

A chart of current and voltage, sample rate can be configured.

In the configuration it is possible to select between a couple of predefined color palettes.

This usb meter can have a build in bluetooth transmitter, this makes it possible to record logfile on a smartphone.
I would have prefered more values in the log, most important time, but also Ah, W and Wh would be nice.

These usb meters are very easy to open, there is only 8 screws to remove.

The TFT display with a frame that contains the background light.

The bluetooth module. This adapter can be bought with or without it mounted. There is also some very small pogo pins.

I am guessing a bit with these chips: SE8533 is a 3.3 volt regulator, SE8550 is a 5 volt regulator, CBKW is a 18 bit ADC with build in amplifier, FM24CL is the FRAM memory. DALE R012F is the series resistor that is used to measure current over. 32F030F4P6 is the microprocessor. 2635 could be a usb auto coding chip.


The voltage display is fairly precise with no current flowing (Both voltage and current can be calibrated by the user, I have not changed the calibration).

The current display is also fairly precise and will not change with voltage.
  • The tested usb meter uses software V3.0

  • The voltage readout is within 0.014 volt when unloaded.

  • When loaded the voltage will be closest to the usb input voltage.

  • Current is within 0.005A.

  • The usb meter uses about 12.2mA current with normal brightness, 8.5 when dim and 21 with bluetooth connected.

  • The internal resistance is about 0.12ohm (This includes both connectors).

M1: 35,5°C, HS1: 41,2°C
The above IR photo was taken after 30minutes with 3A, during that time the voltage readout changed 0.2% and current readout 0.1%

I have played a bit with the cable resistance function, it uses ohms law and is as precise as possible. How precise that is depends on how stable the voltage is, how stable the current is and how stable the connection resistance is. With my lap grade equipment I can get within a few mOhm (1/1000 ohm), for that test I did not even change usb connection (That alone can be 30mOhm). With more normal equipment I would not expect better than 30-100mOhm. Even with that tolerance it is very useful to get rid of bad (High resistance) usb cables.


This is a very precise usb meter with many interesting functions. With both good precision and external logging in can be used for testing usb equipment.
The larger and always on display (even with bluetooth enabled) makes it easier to read. The auto coding output can be used as a quick fix when power supply and device do not match, but getting another power supply is a much better solution.


For these USB meters I used precise equipment (Keithley: DMM7510, 2280S, 2460).

How do I make the test

Interesting, thanks!

Neat looking device! Thanks for the review.

How well does the auto coding works?

I cannot say how well it works, I do not have a pile of different phones, but I have seen Apple 2.1A, Samsung and DCP codings on it (This is what I usual see on auto coding chips).

I just received my YZ1270 — looks like a great meter, but the main reason I bought such an expensive (relatively) model was because I was given to understand it could “force” different USB codings. I worked out to hold the button while plugging the meter in to get settings, and how to view the different graph modes (long press), but holding the button on the coding screen (displaying D+ & D- voltages) only seems to flip rotate the display 180 degrees. Long presses on the W/Ohm and Wh/Ah screens just seems to change to different data storage slots.

Was I wrong about being able to force Apple/Android/QC codings, or is the a button method too advanced for my feeble mind?

Yes, from the above review:
The top usb connector has local auto coding, i.e. when using this the power coding on the power supply is ignored.
The bottom usb connector has data connection from the input connector, any usb voltage shown on the display is for this connector and the usb input connectors.

Ok, I think I understand better, thank you!

Thank you for the review of an yzxstudio power monitor. I bought mine a few years ago it was the usb2.0 black version and the newest one. I have not been keeping track of newer products and feel like Rip Van Winkel.

Here is an explanation: https://www.youtube.com/watch?v=IVNA4gvQzKo&index=190&list=PL1t6JkcqG9NkaqDf0TxcfyBgSCxQExoTS

Here is a review of the monitor I have.

Hello to all,
i’ve a question about this YZXstudio1270.
Why it has the usb 2.0 and not the 3.0?
What’s the differences between usb2 and usb3 regarding the charging process?
Can i charge an usb3.0 device using the YZX1270? Which are the limitations?
Thanks a lot

The difference between usb2 and usb3 is two extra data connections and has nothing to do with charging, i.e. the only time you need a usb3 voltmeter is if you want to measure current consumption while transferring data at very high speed in the same cable.
With usb-c the charging may be different.

I got two ZY1270 meters. I plug one to top port of another to so see it codings.
So… Top port of ZY1270 has fixed Apple 5V 2.1A coding, and bottom port is using pass through coding from power supply.
So the question is: will Fast Charge feature be working only on Apple devices as it is coded to force Apple 2.1A coding ? Is it possible to choose another coding on fast charge port on ZY1270 meter? For example I would like it to be coded as Samsung 2.0A?

here is the photo of forced top usb coding:

Auto coding chips will usual look like Apple 2.1 or Apple 2.4A coding, but will change to another coding when required.

how is it detected: “when required” ??

Looking at the voltage and pulsing on the data pins.

“2635 could be a usb auto coding chip.”

Do you know where can I find some specification about this chip ?

If I had found any specification I would not have said “could be”, but “is”.
There is very little doubt about it, it has two pins that looks like they are connected to the usb connector.

Okey you were right. The chip name is UC2635. I found specification on this site: http://wenku.baidu.com/view/e3660480f8c75fbfc77db2ec.html###, I dont know how to download full pdf text from this page so I made some screenshots of first 4 (and only?) pages. You can see it here: Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.. I found also UC2631 pdf you can download it also in this folder.

In my opinion Auto Fast Charge on Samsung Devices is not working as it should. It always emulate Apple 5V 2.1A. Even when I connect ZY1270 to DCP 5V 1.5A and try to power Samsung Galaxy Tab it always shows Apple 5V 2.1A but I think it should switch to Samsung 2.0A. When I charge Ipad it works very good and talking much more power compare to port without emulation(direct DCP 5V 1.5A).

The auto coding does not always work perfectly, but for when the charger has forced wrong coding it helps a lot… I had a defective powerbank stuck with “USB 480MBPS” coding and wouldn’t charge anything past 1A, and this meter fixed the issue.