Inline process refractometer
Encyclopedia
Inline process refractometers are a type of refractometer
designed for the continuous measurement of a fluid
flowing through a pipe or inside a tank. These refractometers typically consist of a sensor
, placed inline with the fluid flow, coupled to a control box. The control box usually provides a digital
readout as well as 4-20 mA analog outputs and relay outputs for controlling pumps and valves. Instead of placing the sensor inline of the process, it can be placed in a bypass, attached by a thin tube.
This measurement
has been an important element in the process control
of the chemical and refining, pulp and paper, food, sugar and pharmaceutical industries for more than a century. For instance, the in-line concentration measurement can be used as a real-time predictive tool for the final concentration
. A quick and accurate response is needed to optimize production. Cost reduction is possible by reducing the variation of mean average of the product concentration. The cost saving is related to the value of the component being measured.
A digital inline process refractometer sensor measures the refractive index
and the temperature
of the processing medium
. The measurement is based on the refraction of light in the process medium, i.e. the critical angle of refraction using a light source. The measured refractive index and temperature of the process medium are sent to the control box. It calculates the concentration of the process liquid based on the refractive index and temperature, taking pre-defined process conditions into account. The output is typically a 4 to 20mA DC output or, increasingly, an Ethernet
signal proportional to process solution concentration, liquid density, Brix or other scale that has been selected for the instrument.
Refractometer
A refractometer is a laboratory or field device for the measurement of an index of refraction . The index of refraction is calculated from Snell's law and can be calculated from the composition of the material using the Gladstone-Dale relation....
designed for the continuous measurement of a fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
flowing through a pipe or inside a tank. These refractometers typically consist of a sensor
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
, placed inline with the fluid flow, coupled to a control box. The control box usually provides a digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
readout as well as 4-20 mA analog outputs and relay outputs for controlling pumps and valves. Instead of placing the sensor inline of the process, it can be placed in a bypass, attached by a thin tube.
This measurement
Measurement
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the metre, second or degree Celsius...
has been an important element in the process control
Process control
Process control is a statistics and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range...
of the chemical and refining, pulp and paper, food, sugar and pharmaceutical industries for more than a century. For instance, the in-line concentration measurement can be used as a real-time predictive tool for the final concentration
Concentration
In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...
. A quick and accurate response is needed to optimize production. Cost reduction is possible by reducing the variation of mean average of the product concentration. The cost saving is related to the value of the component being measured.
A digital inline process refractometer sensor measures the refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
and the temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
of the processing medium
Processing medium
In industrial engineering, a gaseous, vaporous, fluid or shapeless solid material that plays an active role in manufacturing processes - comparable to that of a tool.-Examples:...
. The measurement is based on the refraction of light in the process medium, i.e. the critical angle of refraction using a light source. The measured refractive index and temperature of the process medium are sent to the control box. It calculates the concentration of the process liquid based on the refractive index and temperature, taking pre-defined process conditions into account. The output is typically a 4 to 20mA DC output or, increasingly, an Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
signal proportional to process solution concentration, liquid density, Brix or other scale that has been selected for the instrument.