Isolated EC Probe Interface

Monitor hydroponic nutrient levels or salinity in pools.

  • Electrical Conductivity in Siemens (0.5 - 20.0 mS/cm)
  • Total Dissolved Solids in PPM (250 - 10,000 PPM)
  • Salinity in PSU (2 - 12 PSU)
  • Temperature in Celsius/Fahrenheit (-55 - 125 C)
  • Electrically Isolated
What it is

An electrically isolated I2C sensor device, a waterproof temperature sensor, and an electrical conductivity probe. It measures the conductivity of a solution and converts it into Siemens (S) total dissolved solids and salinity. The firmware allows for single or dual-point calibration with temperature compensation.

The board uses the Qwiic Connect System for wiring, it’s an easy-to-use, polarized, push-to-fit connector. No more mistaken connections or soldering header pins.

Using it

Read the documentation on the specifications, setup, and use of the device.

The library to use it is in the Arduino and IDE. A python and rust implementation for Raspberry Pi is available. There is also a MicroPython library.




Probe Selection

Any 2-electrode probe with a BNC connector and a cell constant of 1K can be attached to the device. EC probes are specified by their cell constant (K).

A probe with a cell constant of 1K is appropriate for hydroponics and saltwater pools.


When different probes are connected to the same controlling device, they can cause interference. The environment also causes interference due to ground-loops or other electrical noise like pumps. Electrically isolating the probe from the controlling device can help to prevent it.

All μFire probe interfaces come with electrical isolation hardware which provides a stable, isolated power supply and I2C bus between the interface and your controlling device.

Buy it

The board can be purchased by itself, conductivity probes are also available separately.

EC Probe Interface

The board by itself. - $50.00

Waterproof Temperature Sensor

A DS18B20 temperature sensors enclosed in a waterproof housing. Measure from -55 to 125 C. It includes a convenient polarized connector and 1 meter of cable to easily attach it to uFire devices. - $7.00

Conductivity Probe

Black platinized in a glass body, 1K with a BNC connector. - $40.00

Qwiic Wires

Qwiic to Board - $1.50

Qwiic to Male - $1.50

Female to Qwiic - $1.50

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Support and Questions

If you have questions, find a bug, or have any suggestions, go to this project’s GitHub page and submit an Issue or Pull Request. Or you can send an email to [email protected].

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