LowPowerLab Current Ranger R3 MK6 Current Sense Amplifier (with Display)

The CurrentRanger R3 MK6 from LowPowerLab is a precision auto-ranging current sense amplifier designed for engineers, makers, and researchers who need to measure extremely low currents accurately — from picoamperes to amperes — across a single instrument. It is particularly valuable for characterizing battery-powered, low-power IoT and embedded systems where sleep currents can be in the nanoamp range while active currents jump to hundreds of milliamps.

At its core, the CurrentRanger uses two MAX4239 ultra-low-offset auto-zero amplifiers (6 MHz unity-gain bandwidth) configured for a total 100× output gain, combined with three high-precision shunt resistors (10mΩ, 10Ω, 10kΩ) to deliver three current ranges with 1mV output per nA/µA/mA. The analog signal is sampled by the on-board SAMD21G18 ARM Cortex-M0+ microcontroller running at 48MHz, which also controls the digital range switching, touch interface, OLED display, USB output, and power management.

Unlike a traditional rotary-switch current meter, range switching is fully digital and glitch-free — controlled via capacitive touchpads on the top of the PCB with an optional buzzer for acoustic feedback. The auto-ranging engine can jump between any of the three ranges (even from nA directly to mA) without bouncing or interrupting your measurement.

The R3.MK6 revision brings several practical improvements: a USB-C connector (sturdier and non-polarized), an SMD side power button, firmware v1.1.4, and an optional 1200mAh battery designed specifically for the CurrentRanger. The included 0.96" OLED display makes the device usable in standalone mode, while the banana plug sockets and pin headers let you connect to a multimeter, oscilloscope, or DAQ for advanced analysis. Optional Bluetooth modules enable wireless data logging for long-duration current profiling.

Important note: To keep cost low, there is no galvanic isolation between the input, output, USB port, and pin headers. Always read the manual at lowpowerlab.com/guide/currentranger before use — ground loops or accidental current paths from input to output or USB can damage the device.

Specifications

Current Ranges

• Unidirectional mode: 0 to 3300 nA / µA / mA
• Bidirectional mode: ±0 to 1650 nA / µA / mA
• Output scaling: 1mV per nA / µA / mA

Burden Voltage (ultra-low)

• 17 µV/mA (mA range)
• 10 µV/µA (µA range)
• 10 µV/nA (nA range)

Accuracy

• ±0.05% on µA and nA ranges
• ±0.1% on mA range

Resolution (nA range)

• 100 pA (3.5-digit reading)
• 10 pA (4.5-digit reading)
• 1 pA (5.5-digit reading)

Other Electrical Specs

• Output offset voltage: typically <10 µV, max 50 µV
• Maximum allowed input voltage difference: 33 mV
• Bandwidth: >300 kHz (-3dB)

System

• Microcontroller: SAMD21G18 ARM Cortex-M0+ @ 48MHz, 12-bit ADC
• Amplifiers: 2× MAX4239 auto-zero, 6MHz GBW
• Shunt resistors: 10mΩ, 10Ω, 10kΩ (high precision)
• USB: USB-C (R3 MK6), CH340C serial chip
• Display: 0.96" OLED (optional/included with display version)
• User interface: Capacitive touchpads + buzzer
• Power: LiPo battery (JST), USB-C charging, auto power-off
• Firmware: v1.1.4, open-source (GitHub), UF2 bootloader for easy updates
• Enclosure: 3D-printed PLA case with mounting screws
• Protection: Reverse polarity protection (added in R3)

Applications

• Low-power IoT device current profiling (e.g. LoRa, BLE, Zigbee nodes)
• Battery life estimation for wearables and embedded products
• Sleep current measurement of microcontrollers (Arduino, ESP32, STM32, nRF, etc.)
• MCU power optimization during firmware development
• Sensor module characterization
• Solar harvesting and energy harvesting circuit analysis
• Quiescent current testing of analog circuits
• Transient current capture with oscilloscope (fast wake-up/TX pulses)
• Educational labs in electronics and embedded systems
• R&D test benches for hardware engineers