Process-Refractometer

SCHMIDT + HAENSCHOptisch-elektronische Meßinstrumente seit 1864

• Online, real time refractive index, Brix or concentration measurement to monitor and control the concentration of dissolved solids in solutions or liquids in mixtures in the process.

• Reliable measuring head featuring a sapphire or YAG prism, CIP capability (pipe pigs usable). Construction fulfills sanitary regulations of the food and pharmaceutical industry.

• Advanced microprocessor controller (electronic unit) for data processing from high resolution photo diode array, display/keyboard functions and remote transmission.

• Continuous measurement and real time process control with analog and digital outputs, limit comparator, internal diagnostics and programmable temperature compensation.

• Automatic temperature compensation for Brix scale is standard, for other scales is programmable.

• Reasonable investment. One electronic unit can be used to control up to 3 sensors (iPR2) or the sensor does not need an electronic unit at all (iPR3).

Schmidt+Haensch’s process refractometersiPR2 and iPR3

They determine the refractive index of a process solution, a binary or quasibinary liquid mixture by measuring the critical angle of total reflection. The refractive index cor-relates with the concentration of the solution or liquid mixture.

Working principle

Super-sensitive light detector, precise algorithm and temperature compensation boost resolution and precision.

Both measuring heads work with a similar configuration. The difference between the two models is the electronic controller.

A LED emits light, which is transmitted by a glass fiber to one side of the measuring prism and then deflected to the boundary surface prism/sample. The light rays meet this surface at different angles, they are partially and totally reflected and partially refracted into the process solution. In this way, the optical image is divided into a light and a dark area. Reflected light is propagating to the other side of the prism and then through a filter to a photo diode array. The partially and totally reflected rays are detected with a high-resolution array consisting of 2048 photo diodes. The position of the borderline between the light and dark areas shows the value of the critical angle and thus the refractive index of the process solution.

The Brix measurement is temperature compensated for the process stream conditions, generating both high resolution and high accuracy. The customer can program up to 30 special scales using a polynom of 8th degree. For each of those scales the temperature correction is programmable seperately.

Superior benefits

Continuous, drift-free measurement creates tight process control.

The iPR’s measure the refractive index continuously and thus, the concentration of a binary or quasi-binary liquid mixture. The measurement is independent of light inten-sity from the light emitting diode (LED) and is free ofsignal drift, granting high precision and better processcontrol. Color, turbidity, undissolved particles or gas bubbles do not affect the measurement.

Construction and materials minimize service and maximize reliability.

The stainless steel (316L SST) sensor head features a sapphire or YAG prism that is both chemically and mechanically resistant to acids, slurries or solvents and complies with foodstuff regulations. The sealing material is Viton, special sealing material is available (i.e. Kalrez). For concentrated acids or highly corrosive substances and processes where stainless steel is not appropriate, the model iPR2 can be delivered with a Teflon flow-through adapter to be installed as a bypass measure-ment. The model iPR2 is also available as an intrinsically safe (EX) model. Using the water-cooling connected to the iPR makes it suitable for high temperatures of up to 150°C. For processes, where the substances cause fouling on the prism, an optional cleaning device using water, steam or solvent is available. For processes where no such addition is allowed, a special ultrasonic cleaning device is available but only for the VariVent mounting type. For high refractive index applications like phenolic resin a model with a measuring range from 1.4 to 1.592 RI is available.

small refractive index

bright dark

large refractive indexlight source

photo diode array

angle of total reflection(critical angle)

total reflected light

YAG prism

opticalglass fibre

refracted light

process solution

Borderprism/solution

IPR2 measuring head with cleaning nozzle

Easy and flexible installation

The iPR measuring head can be installed in pipes, reactor vessels, mixing tanks, kettles, boiling pans and evapora-tors, using different weld-in flanges. It does not depend on a certain flange standard but it can be adapted tomany existing connections, also customer-tailored.The maximum configuration of the model iPR2, means up to three sensor heads, can be connected to one elec-tronic unit, so measurements at three sampling points can be monitored or controlled. The other possibility is that three different sensors can be connected to theelectronic unit to built up an intelligent sensor station containing for example a refractometer, a turbidity meter and an alcohol sensor. A lot of additional combi-nations are possible. This exceptional feature provides considerable cost saving to the customer by eliminating the need to purchase additional electronic units. Subse-quent installation of cleaning devices is possible.

The favourite process connection is the VariVent inline housing. This type of connection provides a maximum of flexibility. It has a hygienic approval, can handle pres-sures up to 15 bars, holds no dead spaces around the measuring head. The basic installation provides the pos-sibility to use pipe pigs where they are useful. The mea-suring head is not disturbing this cleaning technique.

The VariVent mounting is even available for a 90° angleinstallation where the process stream is directly approa-ching the prism and a cleaning device for liquid cleaning is installable in this kind of mounting.

Due to the flexible design of the measuring head of all the models the instrument can be installed in many different applications. The process refractometer is not

limited to one specific process connection or installation point.

Maximum flexibility for output and menucustomization

The electronic unit used for the model iPR2 provides high flexibility and can be used as a small process control station where no supervisory system is yet installed. No external power supply is necessary, the measuring head is supplied via the electronic unit. The data signals are processed by the electronic unit and can be trans-ferred via three isolated 4 to 20 mA analog outputs and up to 8 digital outputs for recorders, printers, pro-grammable logic controllers (PLC) and distributed control systems (DCS). The output can also be used for remote communication links and limit comparators for alarms and to activate valves, pumps, apparatus, etc. allowing direct real-time process control. The three separate4 to 20 mA signals and the measuring equation’s slope and offset can be individually calibrated for specific applications. Menu flexibility includes the ability to bring specific menu-driven operations into the initialization process and/or to assign them to specific keys on the electronic unit. Using his measuring data, the customer can program a display including refractive index, tem-perature compensated refractive index or refractometric dry substance (RDS %) of his substance.

The configuration of the model iPR3 is done through a Windows based software program. Via the RS232 a PC can be connected for the configuration of the analog outputs and other specific settings. The customer needs to supply a 24 V power and can connect up to two4 to 20 mA outputs to his control system. The connections are made through M12 industry standard plugs.When a display is needed the system can be connected to an optional display box which already contains a power supply for 24 V and two relais for using the limit comparators of the measuring head.

VariVent mounting accessory

Technical comparison

Schmidt+Haensch followed two different approachesto supply a solution for the customers applications.

The process refractometer iPR2 is a modular system designed for covering more than one measuring site or more than one sensor type controlled by oneelectronic unit.

The process refractometer iPR3 is designed to fit into a single measuring site where the whole process iscontrolled via a supervisory system.

iPR2

The basic configuration consists of a measuring head and a controller. The controller has a free configurable LCD display, a keypad for data input, menu selection and programming and a serial interface RS232.

The most important features and options are:

• 4 measuring ranges for highest precision

• Up to 3 sensor heads per controller

• 3 separate 4 to 20 mA outputs - programmable

• Analog input board for other sensors (i.e. turbidity)

• Second serial interface

• 8 digital outputs (for limit comparators)

• Relay output

• Easy programming

• Up to 30 special scales programmable, each with separate temperature compensation

• Resolution of up to 0.02% RDS

• Teflon (PTFE) by-pass adapter for high corrosive sub-stances or sensitive processes

• Explosion proof version (class: ib II A T4)

• Electronic unit is splash proof acc. Nema 4 / IP65

• Process temperatures up to 150°C

• CIP and pipe pig use possible

iPR3

The iPR3 is a stand alone process sensor, which does not require an exterrnal electronic unit. Its special design and electronic configuration makes it highly flexible and very easy to operate.

The most important features and options are:

• One measuring range for highest flexibility

• No control unit necessary

• 2 separate 4 to 20 mA outputs - programmable

• Serial interface RS232 or RS485

• 2 digital outputs (for limit comparators)

• Easy programming with Windows software

• 2 special scales programmable, each with separate temperature compensation

• Standard resolution 0.1% RDS

• Process temperatures up to 150°C

• Optional display and relay box

• CIP and pipe pig use possible

Teflon bypass for high corrosive liquids and semiconductor processes

VariVent weld in flange for vessel mounting with cleaning nozzle

Intrinsically safe unit (EEx ib II A T4) with VariVent connection

90° angle VariVent mounting with hose connection

Installation with water cooling and ultrasonic cleaning

Installation in crystallizer with cleaning and water cooling

Installation in small circulating process with pump

SCHMIDT+HAENSCH GmbH & Co.Waldstraße 80/81D-13403 BerlinGermanyPhone: +49 30 / 41 70 72-0Fax: +49 30 / 41 70 72-99e-mail: sales@schmidt-haensch.dewww.schmidt-haensch.de

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SCHMIDT + HAENSCHOptisch-elektronische Meßinstrumente seit 1864

Applications

Chemical IndustryInorganic acids and basesFats and oilsOrganic products and solventsSalt solutionsPulp and paperPaints and glues

Petrochemical IndustryParaffins, waxesPetrochemical products (intrinsically safe version available)Resins

Semiconductor IndustrySlurries, hydrogen peroxide, hydrofluoric acid

Food IndustryJuice, fruit concentrateSoft drinksWine, beerCoffee, coffee extractMilk products, yogurtTomato paste, ketchupJams, jellies, marmaladesCandies, ChocolateStarch

Sugar IndustryRaw juice, thin and thick juiceMassecuite, molassesLiquid sugar, press waterCrystallization pansFructose, glucose, sucrose

Textile IndustryPoly Vinyl Alcohol