Test/Review of YZXStudio USB meter ZY1266

YZXStudio USB meter ZY1266

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 f-t-2000, he is also known as Franky or 99centhobbies

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 (The above shop sells the tool and gives access to the updates).

This table compares some of the YZXStudio usb meters.

How does it look

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

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

The first screen, it shows V, A, Ah and time, the “0” is selected memory bank.

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

This screen shows usb coding and voltage. From voltage and current the resistance of the load is calculated and shown. 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.

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.

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

This usb meter can have a build in bluetooth transmitter, this makes it possible to record logfile on a smartphone. Using bluetooth will disable the backlight, this makes the display a bit difficult to read.
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.

LCD display with a led in the frame.

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, CBAY 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.
The microprocessor is hidden beneath the flex cable.


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

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

  • The voltage readout is within 0.005 volt when unloaded.

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

  • Current is within 0.002A.

  • The usb meter uses about 11.2mA current with backlight on, 6.3mA with backlight low and 16.5 with bluetooth connected.

  • The internal resistance is about 0.095ohm (This includes both connectors).

M1: 37,7°C, HS1: 40,3°C
The above IR photo was taken after 30minutes with 3A, during that time the voltage readout changed 0.2% and current readout 0.003%

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.


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

How do I make the test


regarding the bluetooth serial connection - with a good serial program you can timecode the data when it is received. It will be sufficiently accurate. I think it is simply too complicated to have accurate timekeeping that can survive power failures on the devices.

I did not expect it to survive a power failure, the bluetooth connections will also break if the power fails.

Received mine today…
Can’t get it to ‘bluetooth’ though :slight_smile: Already set it to data in the settings (where you set brightness/upload)

It should work provided bluetooth is set to 1 in usb-meter settings and your computer/phone supports BluetoothV2.1+EDR. Do you have a problem with connecting or pairing or you don’t see it at all?

Don’t see it at al, doesn’t show up when scanning for bluetooth devices.

It is called SPP_CA, not anything with YZXStudio!

It showed up after cycling through the options in the settings.
Thanks guys!
Now I finally have a reason to use my Nexus 2013 for something else than an alarm clock ;à

Next question, you mention the cable test function.
Am I right in assuming I’m doing it wrong when I just connect a constant load to the meter and use the micro-usb plug to power it via the cable that is being tested?

You have to get a reference first, i.e. plug it into the power supply with the load then hold the button down to copy the measurements into reference.
Next you take the meter out and uses the cable to connect it to the power supply, the load must still be connected with the same setting. Using normal usb or micro usb is not very important.

Verify that the current is very close to the reference current, the the ohm value will be fairly correct.

You can also try pushing on the cables connectors and see how much the resistance changes, if the connectors are worn it can be more than 0.05ohm.

I believe Banggood is selling them now too. Or maybe they have been for some time, even. I noticed it last night.
They’re quite a bit cheaper than elsewhere too :

That is relative, they are much cheaper than Franky and the YZXstudio products cost more than the cheap usb monitors.
In my opinion you also get considerable more. Is it worth the price? That can always be discussed, I prefer lab equipment when I test stuff, but I do like the YZXstudio devices for fast checks.

I meant that nicely priced as a positive :slight_smile: Changed my post to reflect that.
To me, it’s definitely worth the price I paid.

I got my unit a few days ago from Franky, and I am impressed with the unit :+1: My problem is, I can get the Auto Backlight working.

Under Settings, 06 Auto Backlight is set to 001mins, and 03 Brightness is set to 001. Should this then not enable the backlight to automatically switch off after a 1 minute?

Mine does the same. And when the brightness is set to 2, it drops down to 1 after one minute. Firmware 3.0.

Just tested mine, with the same result. Maybe auto Backlight then simply dims the display, and not switch off the backlight? (Also Firmware 3.0)

The backlight is permanently on, it just drops to a very low level.

Cool, now just add the YZXStudio Power bank to your store, please :slight_smile:

Already in stock now.