In-Line Industrial 
Process Refractometers Transmitters

Schmidt + Haensch Process Refractometers
The iPR series process refractometer are for monitoring, recording and controlling the concentration of dissolved solids in a process line. The IPRs accurately measure refractive index, temperature, and readout in index, compensated Brix and other standard and custom concentration scales. These refractometers are critical angle refractometers built around a sapphire prism and a high resolution photo diode array. The refractive index measurements are not influenced by the color or turbidity of the sample.

Inline process refractometer


  • High Resolution in Brix and Index
  • Stable and repeatable operation even at high temperatures and pressure
  • Adaptable to most piping systems including aseptic systems
  • Multi head configurations
  • Index transmitter configurations
  • Analog and relay outputs
Working Principle

The light from an LED source is transmitted by a fiber optic onto one side of a measuring prism and internally reflected to the interface of the prism and the sample liquid. A portion of this light beam is reflected back onto the opposite side of the prism at an angle which depends on the refractive index of the liquid at the interface. The position of this reflected beam, as it exits the prism, changes with the angle of reflection (which depends on the refractive index of the sample ). A linear diode array is used to accurately detect the varying position of the reflected beam and this position is calibrated with respect to refractive index. As there are no moving parts, only precise optical and electronic elements, the calibration is very stable, repeatable and accurate.

process refractometer principle of operation

Built for processing environment

The iPR series refractometers are designed for reliability in tough process environments. Measurements are not influenced by color or turbidity and the refractometers can be used for a wide variety of dissolved solids applications.

Suitable for many in the food and sugar industry as well as chemical and effluent monitoring systems.

The iPR is ideal for juice, juice concentrate, beverages, soft drinks, wine, beer, coffee, milk products, jams jellies and tomato pastes. And massecuit, molasses, press water, liquid sugar, fructose, glucose and sucrose.
Industrial applications include acids, bases, fats, oils, solvents, pulp, paper, paint, glue, paraffin's, waxes resins etc..

The refractometer can be supplied with adaptors for most process lines including Tri Clover and Tuchenhagen style aseptic systems. The IPRs can also be supplied with special fittings for monitoring flow in smaller pipes down to 0.25 inches diameter.
For sticky materials the adaptor flange can be fitted with a cleaning nozzle.

In Situ cleaning 

The illustration shows a refractometer head with a cleaning nozzle opposite the prism face viewed through a cutaway in the Tuchenhagen flange. This kind of cleaning device can be used with any of the IPR in line refractometers

refractometer with cleaning nozzle
Measuring head adaptable to any location
The stainless steel refractometer head can be mounted into pipes, kettles, or other vessels with the aid of suitable fittings. You can specify the fittings you need and our engineers will work with you to provide a configuration for your process. We also offer Tri Clover, aseptic and Varivent Tuchenhagen flanges.
Mounting Arrangements
Mounted in 90 degree elbow hose connections Mounted in flange for tank or vessel with cleaning nozzle
Water cooled head with ultrasound cleaning Mounted in T to a pump

Selection Guide

Product Links
Product Description
All these process refractometers are designed as refractive index transmitters for direct insertion into a pipeline or tank. They measure the refractive index continuously as well as the concentration of a binary or quasi-binary liquid mixture. The measurement is independent of light intensity and is free of signal drift, thus producing high precision monitoring and better process control. Colour, turbidity, undissolved particles or gas bubbles do not affect the measurement.
iPR Compact 2

Measuring Range: 1.3320-1.4209 RI 0-50 Brix(w/ ATC)
Resolution: 0.0001RI /0.1

IPR compact is an economy model featuring small size robust performance for many routine applications.
Designed to be air cooled and therefore suitable only when the process temperature is not exceeding 80°C

iPR Basic 3

Measuring range : 0 - 90 Brix / 1.3200 - 1.5200 RI>

Resolution: 0.01 Brix / 0.00001 RI

Replaces the B2 series. Features extended range and accuracy compared to the compact model. Designed to be air cooled and therefore suiatble for most process with process temperature not exceeding 90°C

iPR FR 2(Full Range)

Measuring range: 0 - 95 Brix / 1.3320 - 1.5300 RI

Resolution: 0.01 Brix / 0.00001

The IPRFR2 is a full range high accuracy instrument suitable for most every application.
It includes a local LDC display. The head is fitted with a water cooling circuit which allows the refractometer to be used with higher temperature processes up to 150 °C


iPR HR 2(High Resolution)

Measuring Range: 1.332000 - 1.372000 RI / 0 - 25 Brix
Resolution: 0.000005 RI / 0.002 Brix

The iPR HR is specially developed for the check of liquids with very low solid concentrations (e.g., Light drinks). It measures with high accuracy over a limited range of index and Brix

iPR Ex-Protection

Measuring range: 0 - 95 Brix / 1.3200 - 1.5200 RI

Resolution: 0.01 Brix / 0.00001

The ex-proof version of the process refractometer consists of an intrinsically safe sensor installed in the hazardous area and a barrier unit and an electronic unit installed in the safe area, European classification ATEX ib II A T4.

iPR Mounting Accessories iPR Mounting Guide Pdf