With over 40 years in the water quality business and customers like IBM, Seimens, and Lawrence-Livermore Berkeley Labs, pHionics has the experience and products you need to succeed.

The D-pHi Series™

4-20 mA Differential pH Sensor

Only $549 USD


Recommended for process control, wastewater, aquaculture, hydroponics, environmental remediation, and other applications requiring extremely stable, user-friendly, and low-maintenance pH monitoring.

Have a question?

We have knowledgeable engineers ready to help with your project!

Business hours:

9 am to 5 pm PST – Monday through Friday


  • Refillable electrode that never needs replacement
  • Chemical-resistant titanium and Delrin® housing (PVDF available)
  • Built-in 0-50°C temperature sensor (secondary 4-20 mA output)
  • 3/4 or 1 NPT backend (depending on model)
  • Fully submersible to 100 psi and 150°F
  • Dry storage
  • Automatic Temperature Compensation (ATC)


The d-phi Series is fully submersible up to 100 psi

Model D-phi-s/i


Model D-phi-s has a 3/4″ NPT thread for standpipe mounting.

Model D-phi-s


Mount model D-phi-i inline up to 100psi with the built-in 1″ NPT thread.

Model D-phi-i

Additional Resources

pH Sensor Mounting Options

pH Sensor Inline and Standpipe Mounting Guide

pH Sensor

pH Range 0-14 pH
Output 4-20 mA | 2-wire
Electrode Type Differential
Wetted Materials Delrin®, titanium, glass, Viton™
Operational Temperature Range 32-155°F (0-70°C)
Thread Type 3/4 inch MNPT or 1 inch MNPT
Max Flow Rate 10 ft per second
Pressure Range 0-100 psi
Automatic Temperature Compensation 32-155°F (0-70°C)
Power Supply Voltage 8-40 VDC
Warm-up Time 2 seconds
Response time 96% < 5 seconds
Length 9.25 in (23.5 cm)
Width 1.00 in (2.54 cm) max.
Weight (No cable) 0.50 lbs (0.227 kg)
Linearity ±0.014 pH*
Accuracy ±0.014 pH*
Sensitivity ±0.01 pH

*After proper calibration


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

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.

Related Products

STs Series ORP Water Quality Sensor and Transmitter

STs Series Conductivity Sensor

STs Series Dissolved Oxygen Water Quality Sensor and Transmitter

STs Series Dissolved Oxygen Sensor

STs Series ORP Water Quality Sensor and Transmitter

STs Series ORP (redox) Sensor