DTU-1705L USB Tester

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Official specifications:
This is a USB meter with protocol trigger.

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I got the meter in a cardboard box, with specification on the back.

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It contained the meter and a instruction sheet in English and Chinese.

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The user interface is fairly simple, short presses on the two button changes screen or steps a value up/down, longer presses will activate/cancel configuration.

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Display and functions


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The main screen with voltage, current and power. There is also data line voltage and load equivalent resistance.

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Voltage and current with power, capacity and time.

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Protocol analyzer, shown detected protocol, voltage on data lines.

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Calculate resistance in a cable, this requires a constant load and a stable usb supply. Then the reference voltage can be stored with load and without cable, adding the cable when reference is stored will show the resistance in cable and connectors.

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Protocol search and trigger, hold down button to activate.

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Each supported protocol has a trigger screen.

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After the trigger screens is the auto detect mode. This screen is remembered when power is removed.

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The charting function is designed to show a full charge curve, the fastest update rate is once a minute. The curve is saved.

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There are a couple of configuration screens, Voltage, current, time out, log rate, back light, factory reset.



Measurements
Voltage

The voltage display is very precise with no current flowing.

Current

The current display is also very precise up to 3A, then the precision drops some.

Temp6020

M1: 36.7C, HS1: 54.7C

Temp6021

M1: 44.5C, HS1: 57.2C

The above IR photo was taken after 30minutes with 5A.
The current varies with temperature, I got 1% change after 30 minutes with 5A.



Tear down

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It was easy to open with four screws. Notice the two buttons are not the same, this prevents assembly faults.

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The meter is based around a microprocessor (MM32F031K6T Arm M0), with support from a EEPROM (U4: 24C08AN) and a OpAmp (U1; marked S06AC) to amplify voltage from current shut. The current is measured across a 0.012ohm (12mOhm) resistor. The MPU uses internal 12 bit ADC. The microprocessor uses internal clock oscillator in this circuit, this means the Ah and Wh will be less precise.
And what is the extremely small resistor that is between C13 & U1?

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On this side is the voltage regulator (U3: XC6203A 3.3V). According to the markings on the circuit board there may be a serial port available (A check with an oscilloscope did not show any data).

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Conclusion

A usb meter with protocol analysis and trigger. The chart can be rather useful with the slow time scale, it will show the full charge curve for a phone or tablet. The USB-C functions do not really work.
I like the used interface, it is fairly easy to use, but I do not like that it need about 0.2A before it will show something.


Notes

For these USB meters I used precise equipment (Keithley: DMM7510, 2280S, Keysight: 34470A).

How do I make the test