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  • TUpH retractable pH and ORP sensors
  • Measuring range:
    • 0 to 14 pH
    • -1500 to 1500mV ORP
  • GPHT hemi bulb or GPLR flat bulb
  • Temp range: 32 to 212°F (0 to 100°C)
  • EPDM, Viton, Kalrez O-ring material options
  • Superior chemical resistance
  • TUpH reference technology ensures long life
  • Large surface area reference junction

The Rosemount Analytical 398R / 398RVP pH and ORP Sensors are the ideal sensors for measuring pH in harsh process liquids. Use Models 398R and 398RVP to measure pH in sour water strippers, in pulp bleaching towers that use chlorine dioxide, and in process streams containing a variety of organic solvents.

The TUpH™ reference technology provides maximum life and ensures low maintenance in processes that typically coat reference junctions. Standard porous junctions that plug mean noisy, drifting pH readings and increased maintenance. The TUpH™ junction fights plugging in two ways. TUpH™ junction pores are much smaller than the smallest particles likely to be in the process. Therefore, particles do not block the pores but remain on the surface. And, the large surface area means solids can accumulate on the junction, yet the sensor provides a steady pH signal. TUpH™ sensors also resist poisoning. The long internal helical diffusion pathway hinders poisoning agents, like sulfide, mercury, cyanide, and ammonia, from migrating into the reference electrode.

The AccuGlass™ pH bulb means the Models 398R and 398RVP resist cracking and has near theoretically perfect response even at extreme pH values. A slotted tip surrounding the glass bulb provides additional protection against breakage. The sensor can be oriented with the bulb directly in the stream, or it can be turned ninety degrees, permitting the shroud to protect the glass bulb from particles.

Models 398R and 398RVP use the highest quality of materials to provide superior chemical resistance. Both sensors are housed in a titanium tube. The molded Tefzel® TUpH™ construction is offered with a choice of seals (Viton® or Kalrez®). Combining high quality materials with the TUpH™ reference technology and AccuGlass™ pH bulb allows for ultimate chemical resistance and makes Models 398R and 398RVP the perfect choice for measuring pH in harsh, demanding processes.

Models 398R and 398RVP are available with 15 ft. of cable for wiring directly to an analyzer/transmitter or a remote junction box. The Model 398R retractable sensor is also available with 9.5 in. of cable for use with a sensor head junction box which attaches to the sensor tube via a compression fitting. Due to the high impedance pH signal, a preamplifier must be used and can be housed in the analyzer/ transmitter or junction box. Both sensors are compatible with all Rosemount Analytical and various other manufacturers instruments.


Rosemount Analytical Connector Cable
Lengths of cable with VP8 sensor connectors
In Stock
Rosemount Analytical 23646-01 Extension Cable
11-cond shielded extension cable
Rosemount Analytical 11-conductor Extension Cable


Rosemount Analytical pH Buffer Solutions
pH buffers for the precision calibration of pH meters


Please consider these optional accessories.

Rosemount Analytical Ball Valve Assembly
1.5in, 316 stainless steel, process connector required
Rosemount Analytical 9550220 O ring
2-214, Kalrez, for Process Connector
Rosemount Analytical 23166 Connector
1 x 1in with o-ring groove, in 316 SS or titanium
Rosemount Analytical 23555-00 Junction Box
Compatible with models 54, 5081, 1055 & Xmt preamplifiers
Rosemount Analytical Preamplifier
Preamplifier for remote weatherproof junction boxes
Rosemount Analytical O-ring / EPDM
Quantity of 4, 2-214, EPDM, includes lube
Rosemount Analytical Junction Box Sensor Head
Includes preamplifier, for 54 & 3081
Rosemount Analytical Ball Valve
Ball valve, full port, 1 1/2 FNPT
Rosemount Analytical 99CC Calibration Certificate
One certificate per lot at standard factory ranges only, includes the model, serial and/or tag numbers (does not include actual test data)
Rosemount Analytical Electronic Calibration
Certificate for specific unit, includes model, serial and/or tag numbers, test standards, NIST report numbers, & the actual test data
Rosemount Analytical Certificate of Origin
Original certificate of origin with chamber of commerce stamp


This product can be used in the following applications: