Conductivity Analyzers

What is Conductivity?

Conductivity is the measure of a solution's ability to pass or carry an electric current. The term Conductivity is derived from Ohm's Law, E=I•R; where Voltage (E) is the product of Current (I) and Resistance (R); Resistance is determined by Voltage/Current. When a voltage is connected across a conductor, a current will flow, which is dependent on the resistance of the conductor.  Conductivity is simply defined as the reciprocal of the Resistance of a solution between two electrodes.

How do we measure Conductivity?

There are two basic sensor styles used for measuring Conductivity: Contacting and Inductive (Toroidal, Electrodeless).

When Contacting Sensors are used, the conductivity is measured by applying an alternating electrical current to the sensor electrodes (that together make up the cell constant) immersed in a solution and measuring the resulting voltage. The solution acts as the electrical conductor between the sensor electrodes.

  • The EXAxt450 series covers all Conductivity Applications including all special software functions in the standard analyzers to reduce the number of configurations. This results in less inventory and less training needs for users that have multiple Conductivity applications.

  • The model FLEXA® two-wire analyzer is used for continuous on-line measurements in industrial installations. It offers an option for single or dual sensor measurement, making it the most flexible 2-wire analyzer available. The model FLEXA® modular designed series analyzer offers 4 parameter choices – pH/ORP (oxidation-reduction potential), contacting conductivity (SC), inductive conductivity (ISC) or dissolved oxygen (DO) – with the respective sensor module.

  • Designed to accept two sensor inputs. Differential, ratio, deviation, % passage or % rejection can be indicated and/or transmitted.

  • Intended for the conductivity/resitivity applications in Class I Div I and Class I Div II areas. 

  • The Contacting Conductivity method is especially suitable for low and ultra pure conductivity measurements. The analyzer works with a contacting conductivity sensor with built in temperature element.

  • Intended for the low conductivity applications found in the semi-conductor, power, water and pharmaceutical industries. These analyzers work with contacting conductivity sensors.

  • These analyzers are designed for 2-wire (loop powered) system configuration with Foundation Fieldbus communication. Fieldbus Foundation defines "Fieldbus is a digital, two-way, multi-drop communication link among intelligent measurement and control devices."

  • These analyzers are designed for 2-wire (loop powered) system configuration with Profibus communication.

  • The model FLEXA® two-wire analyzer is used for continuous on-line measurements in industrial installations. It offers an option for single or dual sensor measurement, making it the most flexible 2-wire analyzer available. The model FLEXA® modular designed series analyzer offers 4 parameter choices – pH/ORP (oxidation-reduction potential), contacting conductivity (SC), inductive conductivity (ISC) or dissolved oxygen (DO) – with the respective sensor module.

  • Compact, lightweight, and dripproof, the SC72 is the ideal Conductivity meter for field use. Features wide-range auto-ranging, automatic temperature compensation, self-diagnostic functions, and a large, easy-to-read LCD display.

  • The Inductive Conductivity method is especially suitable for high conductivity measurements. The analyzer works with a sensor with two toroidal transformers built in. An AC current induces a voltage in the process sample that results in a current in the sample. The strength of this current is proportional to the conductivity of the sample following Ohm's law.
     

  • There are numerous industrial applications where measurements and/or control of a specific chemical strength of the process is critical for optimizing the production of the end product. These specific concentrations are obtained by mixing a full strength solution with water to achieve the desired percent concentration.

  • Between measuring plant and control room, especially when the distance between these places is greater than the length of the standard appropriate electrode cables, the connecting equipment can be an expedient method for connecting sensor cables to a measuring instrument.

The measurement of specific conductivity in aqueous solutions is becoming increasingly important for the determination of impurities in water or the concentration measurement of dissolved chemicals.

What is Conductivity?

Conductivity is the measure of a solution's ability to pass or carry an electric current. The term Conductivity is derived from Ohm's Law, E=I•R; where Voltage (E) is the product of Current (I) and Resistance (R); Resistance is determined by Voltage/Current. When a voltage is connected across a conductor, a current will flow, which is dependent on the resistance of the conductor.  Conductivity is simply defined as the reciprocal of the Resistance of a solution between two electrodes.

How do we measure Conductivity?

There are two basic sensor styles used for measuring Conductivity: Contacting and Inductive (Toroidal, Electrodeless).

When Contacting Sensors are used, the conductivity is measured by applying an alternating electrical current to the sensor electrodes (that together make up the cell constant) immersed in a solution and measuring the resulting voltage. The solution acts as the electrical conductor between the sensor electrodes.

What is a 4-Wire analyzer?

This terminology only refers to power supply of the analyzer. It does not have any reference to the number of wires. The 4-wire analyzers separate the power supply from the measurement output. As a minimum we need two wires for the power supply and two wires for the current output of the analyzer. The EXA450 has two analog outputs. four digital outputs. One digital input and of course the sensor input wiring. That is why EXA450 has 6 cable glands. The advantage is that any functions are combined in one enclosure. Local control and alarm functions are possible. In small control installations this is a cost saving feature.

What is a 2-Wire analyzer?

The 2-wire analyzers commonly referred to as Analyzers combine the wires for current output, for power supply and digital communication. The FLXA21 combines the power supply with mA output and HART® communication: all with only two wires plus shield. The advantage is safety (only 24VDC) and simple installation. Just two wires between control room and analyzer. This is an advantage in large scale operations where process control is centralized in the DCS system. 

Overview:

In a semiconductor plant, a variety of chemicals are used in various manufacturing processes. The chemicals used for specific purposes are produced by diluting raw liquid with demineralized water using in diluting equipment, and the control of the concentration at this point is performed by conductivity measurement. 

Application Note
Overview:

To defray energy costs, many industrial plants have their own boilers to generate steam to produce a portion of their energy needs. In addition to generating power, the steam may also be used directly in plant processes or indirectly via heat exchangers or steam jacketed vessels. 

Industries:
Overview:

Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure.

Application Note
Overview:

The kraft process (also known as kraft pulping or sulfate process) describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. Wood chips are by harsh chemicals (white liquor) to produce pulp and spent liquor (black liquor).

Application Note
Overview:

United States Pharmacopoeia (USP) is the governing body responsible for issuing guidelines for the pharmaceutical industry. Implementing these guidelines is required for companies that bring drugs to the US market. This means that USP is important to all pharmaceutical companies, period.

Webinars

    Overview:

    In this 40 min session you will learn the fundamental requirements for aqueous conductivity measurements; the differences between "Contacting" and "Inductive" measurement techniques and which one to use for a particular application. As well as learn the importance of online diagnostics. The goal is to provide participants with simple techniques they can implement to improve their day to day operations and to identify causes of errors and how to correct them

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