Vaisala K-PATENTS® Process Refractometer PR-23-G

Vaisala K-PATENTS Process refractometer PR-23-G is designed for measuring the liquid concentration and density in a wide range of chemicals, fibers, plastics, salts and sodium components. This model is also suited for Brix measurement of sugar solutions in harsh sugar industry conditions. 

The PR-23-G masters highly accurate measuring technology in demanding process control applications where conventional density equipment may struggle due to undissolved solids or bubbles in the process stream. The instrument installs directly into the process pipe or vessel and provides a continuous 4-20 mA or digital measurement signal for real-time process control.

The refractometer system consists of a probe refractometer PR-23-GP or a compact refractometer PR-23-GC and an Indicating transmitter. 

  • Probe process refractometer PR-23-GP sensor comes with flange or clamp connection for the large pipe size and vessel installations. 
  • Compact process refractometer PR-23-GC sensor is intended for the small pipeline and bypass line applications. It is installed in the process either directly in a pipe elbow by a Sandvik coupling connection or in a straight pipe via a Wafer flow cell or a Pipe flow cell. 

The refractometer system features dual connectivity, i.e. one transmitter can operate two sensors. A second sensor can be easily integrated later.

The measurement range covers 0-100 % by weight. The accuracy is typically ±0.1 % b.w. and the measurement is automatically temperature compensated. Low and high concentration alarms can be configured. 

Each sensor is provided with a calibration certificate comparing a set of standard liquids to the actual sensor output. The calibration and accuracy can be verified on-site with the certified Refractive Index liquids. 


  • ATEX approved for Zones 0 and 1, area classification ATEX II 1G Ex ia IIC T4 (only Intrinsically safe PR-23-GP-IA with single sensor transmitter STR).
  • ATEX approved for Zone II, area classification EX II 3 G EEx nA II T4.
  • CSA certified for Class I, Div. 2, Groups A, B, C and D, T4.
  • FM approved for Class I, Div. 2, Groups A, B, C and D, T6.
  • cCSAus certified for Electrical Safety, Sensor: Class I, Pollution Deg. 3; Transmitter: Class I, Pollution Deg. 2; Installation Cat. II.


Universal calibration of each sensor: All sensors are freely interchangeable with each other.
Full measurement range Refractive Index nD 1.3200 – 1.5300, which corresponds to 0-100 % by weight.
Dual connectivity: one transmitter can operate two sensors. A second sensor can be easily integrated later.
Completely digital system: particles and bubbles do not affect operation or accuracy.
CORE-optics: no drift, no re-calibration, no mechanical adjustments.
Ethernet connection and remote panel for data-logging and remote operation.
Process temperature range for compact model PR-23-GC: -40°C...130°C (-40 °F...266 °F), for probe model PR-23-GP -40°C – 150 °C (-40 °F – 300 °F)
Fast process temperature measurement by built-in Pt1000 and automatic temperature compensation.
Simple and easy calibration verification using standard refractive index liquids and a built-in verification procedure at customer site.
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Key Benefits

Designed for harsh environments
Vaisala K-PATENTS Process refractometer PR-23-G combines advanced CCD-camera technology with a rugged steel sensor probe. The probe is designed for demanding process conditions, high temperatures, pressure and vibration.

Special wetted parts materials are available for harsh environments and aggressive process fluids.
Easy and cost effective to install and operate
Process refractometer PR-23-G is installed in the main processing line, bypass line or vessel either directly with Flange or Sandvik L coupling process connection, or via a large variety of cost-effective and easy to mount flow cell options.

PR-23-G includes an Ethernet based communications solution which allows connection to computer networks and to the Internet. Real-time measurement data and diagnostic information may be obtained through this interface, and this makes it also a valuable service tool for parameter changes and software updates.

The refractometer has no lamps or moving parts requiring regular maintenance or recalibration. Users can simply 'install-and-forget', getting a low total cost of ownership.
Accurate and reliable
Vaisala K-PATENTS Process refractometer PR-23-G measurement is based on unique technology utilizing solid-state optics and a CCD-camera to provide a digital measurement of refractive index. The measurement accuracy is ±0.0002 RI (which corresponds to ± 0.1% by weight).

Because of the digital sensing technology, even large amounts of suspended solids, bubbles or color changes do not affect the measurement or the accuracy.