USB meter: Matek USB power monitor

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Official specifications:
I found this unit on Ebay at a dealer called 2012moon816



How does it look

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The device included a manual that explains how to use all the functions.

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The device is two circuit board with screws between. To make a mostly closed box some clear heatshrink is used around it.

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The heatshrink does not close the inside completely around the connectors.

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From the side it can be seen that the display is soldered over the components. The button to select display is also visible.
Somewhere inside there is a buzzer.

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The different displays.



Measurements

Test

The device needs 4.5 volt before the values are shown correctly.
The watt display is not U*I, but slightly below, this may be due to rounding. Also be aware that the voltage is somewhere between Vin and Vout, i.e. the power is neither input or output power, but something in between.



Temp989

M1: 54,0C, M2: 52,1C, HS1: 73,3C

Both the device and the connector get hot.

Temp990

M1: 52,5C, M2: 51,9C, M3: 45,7C, HS1: 70,9C

The transistor to turn output on/off gets rather hot.



Conclusion

This device has some interesting function with mAh and disconnect of output, but 3A is to high a rating for it, the meter will show wrong values.
The voltage range is fairly limited, down to 3.5 volt would have been much better. The software bug with the "end timer" is not a big deal, but it is bad quality control.

The device is accetable and the mAh can be useful, but only if you stay above 4.5 volt and below 2.0A.



Notes

How do I make the test