RD USB Meter AT35



Official specifications:

• Product Model: AT35
• Display screen: 0.96 Inch color LCD display
• Voltage measurement range: 3.700 - 30.000V
• Voltage measurement resolution: 0.001V
• Current measurement range: 0 - 4.0000A
• Current measurement resolution: 0.0001A
• Capacity accumulation range: 0 - 99999mAh
• Voltage measurement accuracy: ±(0.1% + 2 digits)
• Energy accumulation range: 0 - 99999mWh 999.99W
• Current measurement accuracy: ±(0.2% + 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: 0.5Hz
• Quick charge recognition mode: QC2.0, QC3.0, APPLE 2.4A/2.1A/ 1A/0.5A, 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 and QR code where to download it.















There is a single push button on the bottom of the tester.



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 move 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.



Measurements

• The usb meter uses about 16mA and 6mA with display off.
• The internal resistance is about 0.2ohm (This includes both connectors).
• Can only measure current in one direction.
• 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 0.005V when no current is flowing.
• Current display is within 0.005A.
• Software in tester is V1.7

The voltage display has good precision with no current flowing.



The current display is also precise.



M1: 52.2°C, HS1: 54.1°C
After 30 minutes with 4A current.



M1: 47.6°C, HS1: 55.9°C



Tear down



There is no screws, I could just pull it apart.



On this side is the button and a memory IC (HT24LC64).









Here is a voltage regulator (M5333B) and a microprocessor (N76E003AT20: 8051 based 18KB flash, 1KB RAM)











One chip is probably a MUX (U6) and the other a ADC (U2).





Conclusion

This is a small compact usb meter, with easy readable color display, saved Ah & Wh and protocol information. This makes it a very versatile meter with good precision.



Notes

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

How do I make the test