RD USB Meter AT34



Official specifications:

• Product Model: AT34
• Display screen: 1.44 Inch color LCD display
• Voltage measurement range: 3.70 - 30.00V
• Voltage measurement resolution: 0.01V
• Current measurement range: 0 - 4.000A
• Current measurement resolution: 0.001A
• Capacity accumulation range: 0 - 99999mAh
• Voltage measurement accuracy: ±(0.8% + 4 digits under 25°C)
• Energy accumulation range: 0 - 99999mWh 999.99W
• Current measurement accuracy: ±(1% + 4 digits, under 25°C)
• Load impedance range: 1ohm- 9999.9ohm
• Power measurement range: 0 - 120W
• Temperature range: -0°C ~ 80°C / 32°F ~ 176°F
• Temperature measurement error: ±3°C / ±6°F
• Working temperature range: 0°C ~ 45°C
• Product size: 64mmx22mmx12mm
• Refresh rate: 2Hz
• Product weight: 14g (With packaging 28g)
• Quick charge recognition mode: QC2.0, QC3.0, APPLE 2.4A/2.1A/ 1A/0.5Am Android DCP, SAMSUNG

This is a USB meter with color display and fast charge protocol information.




I got the meter in a plastic box, it did not include a manual, but a link where to download it.







There is one push button on the back of the meter.










Display and functions




The main screen with voltage, current, capacity, energy, power, temperature, bank and load equivalent resistance. The temperature is the internal temperature of the tester. There is two banks to store data in.
The icons on the right are different functions, when the button is held down a marker will slowly more down the list, release button to activate that function.
The functions are: Display off, Temperature in °C or °F, change bank, clear bank (Bank 0 is auto reset), flip display.



A fast press on the button will change between the two screens, this is the protocol screen with data line voltage and a guess about the used protocol.



Here a Quick Charge 2.0 protocol is activated and the voltage display shows 12V



Measurements

• The usb meter uses about 16mA and 7mA with display off.
• The internal resistance is about 0.081ohm (This includes both connectors).
• Usb meter will remember measured values when power is removed.
• Bank 0 will show remembered value, but automatic reset when drawing current after a power break.
• Voltage display is within 0.5% when no current is flowing.
• Current display is within 0.3%, except when voltage is below specifications.
• Software in tester is V1.4

The voltage display has good precision with no current flowing.



The current display is also precise.



M1: 47.6°C, M2: 43.6°C, HS1: 48.3°C



M1: 42.7°C, HS1: 48.0°C

The above IR photo was taken after 30minutes with 4A.
The readings did not change, the internal temperature readout showed 58°C



Tear down



There was no screws and I could just break it apart with a spudger.



On this side is the button and a EEPROM (HT24LC64: 8kB 1 million write/word)





The display covers this side, it is mounted with some sticky tape.





The microprocessor is 8051 based (N76E003AT20 18KB Flash, 1k RAM, 12 bit ADC), there is a 3.3V regulator (M5333B: 3.3V) for supplying it.



This side also has a 0.01ohm sense resistor and a OpAmp (Marked 541IG).





Conclusion

This is a small compact usb meter, but the easy readable color display, saved Ah & Wh and protocol information makes it a very versatile meter with enough precision for most usages.



Notes

For these USB meters I used precise equipment (Keithley: DMM7510, 2280S, Keysight: 34470A).
The usb meter was supplied by Rui Deng (RD) for review.

How do I make the test