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. There is a connector available to use a waterproof DS18B20 temperature sensor for 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. Adafruit calls these connectors STEMMA QT.

All boards have a conformal coating to help protect against moisture, corrosion, and short circuits.

Why would I use this?

You would use this sensor device if you want to easily add conductivity measurements to your device.

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.


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 can help to prevent these problems.

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

Buy it

The board can be purchased by itself, conductivity probes are also available separately. A waterproof temperature sensor is highly recommended for accurate measurements.

EC Probe Interface

The board by itself with one Qwiic wire. - $60.00

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

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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