Specializing In 4-20 mA Water Quality Instruments

Simplify your water and wastewater quality measurements with durable, accurate, and easy-to-use sensors compatible with any datalogger or monitoring system that accepts analog inputs.

Explore Products
STs Series Conductivity Water Quality Sensor and Transmitter


STs Series Dissolved Oxygen Water Quality Sensor and Transmitter

Dissolved Oxygen

STs Series ORP Water Quality Sensor and Transmitter

ORP (redox)

All sensors include a built-in 0-50°C temperature sensor.

Example Applications

Autonomous Data Collection

Easily collect large amounts of accurate water quality data around the world by connecting pHionics sensors with remote telemetry units.

Groundwater Monitoring

Take early action on changes in groundwater quality to protect crops or prevent harmful agricultural runoff from damaging local waterways.

Aquaculture Automation

Maximize fish size and reproduction rate by connecting pHionics sensors with SCADA or PLC systems to maintain optimal water conditions.

pHionics STs Series pH Sensor and 4-20mA transmitter in use

The pHionics STs Series™ is more than just a sensor…


Hover over any feature to learn more.

IsolatedA feature that increases safety and accuracy by preventing ground loops.

SubmersibleFully submersible up to 50 psi with cable.

Differential AmplificationImproves accuracy by reducing background noise.

Pre-AmplifierImproves accuracy by strengthening output.

Heavy Duty CablePolyurethane-coated, water-blocked, shielded, Kevlar-reinforced cable.

Field-Replaceable ComponentsCable, circuit board, and electrode all quickly replaceable without any special tools.

Reversible Input ProtectionSimple installation with reversible power and signal wires while also preventing damage to sensor via improper wiring.

0-50°C Temperature Sensor Channel Every sensor includes a secondary 4-20 mA temperature channel.

Visit our Features Page for detailed explanations.

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Featured Article

The Guide to pH Drift

 pH drift is one of the most frustrating issues to troubleshoot because it can seem random and be caused by many different aspects of the environment, maintenance, and sensor design.  This guide provides steps to simplify the troubleshooting process and determine what the cause of drift is along with how to fix it.

Read more…