STs Series Dissolved Oxygen Sensor

Highlighted Features 

  • Galvanic electrode measuring 0-20 mg/L or percent saturation of dissolved oxygen, depending on scaling with attached datalogger or remote telemetry unit (RTU)
  • Large surface area anode for quick response with a rugged membrane
  • Secondary 0-50°C temperature sensor
  • 2-wire, 4-20 mA analog outputs compatible with wide range of dataloggers or remote telemetry units
  • Low power usage

Ranges available:

  • 0-20 mg/L

For datalogging applications, we recommend pairing our devices with the HOBO RX3000.


The pHionics STs Series™ Dissolved Oxygen is a dual-output sensor that pairs with a datalogger or RTU for real-time water quality monitoring.  A narrow diameter allows the STs Series to go where other sensors cannot while a durable, chemical-resistant housing ensures many years in-use.

All parts, including the cable, are easily replaceable without tools using pHionics patented pHiConn™ System, saving frustration and money.  

Starting at $1280 USD

All STs Series base prices include a 25 ft. (7.62 m) cable.  Custom cable lengths available.


Please see our STs Series Dissolved Sensor Oxygen Price List for more information on available options and pricing.  Spare parts pricing is available here.

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Full Features List

  • Galvanic electrode with a large surface area anode to extend electrode life
  • Secondary 0-50°C temperature sensor
  • Chemical-resistant Delrin®, PVDF, and 316 Stainless Steel housing (Titanium optional)
  • Narrow diameter (0.75 inches or 1.9 cm)
  • Removable electrode guard to reduce debris or algae buildup and protect from damage
  • Fully submersible up to 70 psi
  • Shielded, Kevlar®-reinforced, water-blocked polyurethane cable
  • 4-20 mA signal capable of transmission up to 3 miles (with proper wire gauge)
  • Automatic Temperature Compensation (2% per degree Celsius)
  • Reversible Input Protection and Operation
  • Low power usage for long-term water quality monitoring
  • Isolated to prevent ground loops
  • Signal conditioning to remove background noise

Accurate Measurements

No noise. No nonsense.

Experience the difference with our proprietary noise reduction technology.


Dissolved Oxygen Sensor

Output 4-20 mA
Dissolved Oxygen Range 0-20 mg/L (ppm)
Electrode Type Galvanic cell with Teflon membrane
Minimum Flow Rate 1.5 ft (0.457 m) per second
Transmitter Type 2-wire
Automatic Temperature Compensation 2% per °C
Isolation 600 VDC
Operational Temperature Range 0-70°C
Power Supply Voltage 8-40 VDC
Loop Impedance (Max)

200 Ohms at 12 VDC

800 Ohms at 24 VDC

1600 Ohms at 40 VDC

Response time 98% < 60 seconds
Pressure Range 0-70 psi
Wetted Materials 316 Stainless Steel, Delrin®, Viton™, Teflon®, epoxy
Length 14.25 in (36.20 cm)
Width 0.750 in (1.9 cm) maximum
Weight (No cable) 0.50 lbs (0.227 kg)
Linearity ± 0.5% of full scale*
Accuracy ± 2.0% of full scale*
Sensitivity ± 0.05% of full scale
Stability ± 2.0% of full scale
Repeatability ± 1.0% of full scale

*After proper calibration

Temperature Sensor

Output 4-20 mA
Temperature Range 0-50°C
Accuracy +/- 1°C
Linearity +/- 0.5°C
Power Supply Voltage 7-40 VDC


Cable Material Polyurethane
Type 4 conductor, Kevlar® reinforced, water blocked, shielded, twisted-pair wiring
Maximum Distance 3 miles
Resistance per 1000 ft (304.8 m) 26 Ohms
Replaceable? Yes

pHionics products comply fully with all applicable EU Directives to bear the CE Mark.

Delrin® and Kevlar® are registered trademarks of DuPont™.

Viton™ is a trademark of Chemours.

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