Starting at $1,128.00
  • Usually ships in 12 weeks



  • 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 398 / 398VP TUpH pH and ORP sensors are ideal for measuring pH in harsh process liquids. Use Models 398 and 398VP 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 398 and 398VP 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 398 and 398VP 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 398 and 398VP the perfect choice for measuring pH in harsh, demanding processes.


Required Components

These additional components are required for the operation of your product. We strongly advise you to purchase these components unless you already own them or own a suitable alternative.


Mounting Bracket



Please consider these optional accessories.


This product can be used in the following applications: