CurrentRanger

CurrentRanger

Precision auto-ranging current meter (ammeter)

This is my fork for adding a nextion display into the oled header. The variant files need to replace the orginals by lowpowerlab for the board definitions. The changes is to replace the i2c setup with a serialport.

2021-02-11 Added support for a timer that is trigger on going over a current setpoint. Added support for min and max values and prepaired for avg values.

Please see the full guide and latest updates posted here.

Quick Highlights

Here are some of the features of this instrument which sets it apart:

• Low noise zero-offset with 3-ranges (1mV output per nA/µA/mA)
• Low input burden voltage, high precision & bandwidth analog outputs
• Increased flexibility and usability with several input and output terminal options
• Auto-ranging capable
• Use standalone with a small OLED display or with a multimeter/oscilloscope
• Ultra fast range switching between any ranges (even nA to mA) without any glitching/bouncing of a mechanical switch
• Low Pass Filter mode – very useful to capture low noise signals on oscilloscopes
• Unidirectional mode – most used mode in measuring DC currents ranging from [0, 3.3A]
• Bidirectional mode – split supply biasing allows AC currents measurement ranging from [-1.65A, 1.65A]
• LiPo battery powered – long life and extended measurement range
• Auto-power-off
• Full digital control for power & range switching via touch pads
• OLED display option to read output with usable precision
• Datalogging possible via Bluetooth serial module
• SAMD21 Cortex M0+ powered, change firmware to your needs

• Optional buzzer for audible feedback

• Current ranges output:

  • 0-3300 nA/µA/mA (Unidirectional mode)
  • +/- 0-1650 nA/µA/mA (Bidirectional mode)
  • Burden voltage:
  • 17µV/mA
  • 10µV/µA
  • 10µV/nA

• Output offset voltage¹: typically <10µV, max 50µV

• Maximum input voltage differential (see Safety): 33mV

• Accuracy:

  • +/-0.05% (µA, nA ranges)
  • +/-0.1% (mA range)

• Highest resolution (nA range):

  • 100pA (3.5digit meter)
  • 10pA (4.5 digit meter)
  • 1pA (5.5 digit meter)

• Cascaded MAX4239 amplifiers with 100x output gain

  • Bandwidth: >300KHz (-3dB)

Sample no-load mA range comparison to µCurrent GOLD:

Sample measurement of a Moteino waking up and transmitting a RFM69 transceiver packet: