This document discusses conductivity meters, which measure the electrical conductivity of solutions. It describes two main types - contacting meters with electrodes, and inductive meters with wire coils. Conductivity depends on temperature and ion concentration, and is calibrated using standard solutions. Conductivity meters are used to monitor water quality, detect leaks, and ensure cleaning procedures in industries like pharmaceuticals.

1. Conductivity Meter
By
Atif Nauman
(University of Gujrat)

2. Contents
• Introduction
• Principle of Conductivity Meter
• Conductivity Meter Types
• Contacting-type Conductivity Meter
• Inductive Conductivity Meter
• Benefits of Inductive Conductivity Meter
• Drawbacks of Inductive Conductivity Meter
• Temperature Dependence
• Calibration of Conductivity Meter
• Conductivity Meter Applications

3. Introduction
• A conductivity meter measures the amount of electrical current or
conductance in a solution.
• Conductivity is useful in determining the overall health of a natural
water body.
• Conductivity meters are common in any water treatment or
monitoring situation, as well as in environmental laboratories.

4. Introduction
• A conductivity system measures conductance by means of
electronics connected to a sensor immersed in a solution.
• The analyzer circuitry impresses an alternating voltage on the
sensor and measures the size of the resulting signal.
• An integral temperature sensor incorporated into its circuitry
adjusts the reading to a standard temperature
• The units of conductivity are siemens per cm (S/cm).

5. Principle of Conductivity Meter
• The common laboratory conductivity meters employ a potentiometric
method and four electrodes.
• Often the electrodes are cylindrical and arranged parallel.
• The electrodes are usually made of platinum metal.
• An alternating current is applied to the outer pair of the electrodes.
• Conductivity could in principle be determined using the distance between
the electrodes and their surface area.
• Generally for accuracy a calibration is employed using electrolytes of well-
known conductivity.

6. Conductivity Meter Types
Two types of conductivity meters use in industry and Laboratory
• Contacting-type Conductivity Meter
• Inductive Conductivity Meter

7. Contacting-type Conductivity Meter
• Most contacting conductivity sensors consist of two metal
electrodes.
• Usually stainless steel or titanium, in contact with the electrolyte
solution.
• The analyzer applies an alternating voltage to the electrodes.
• The electric field causes the ions to move back and forth
producing a current.
• The charge carriers are ions, the current is called an ionic current.

9. Contacting-type Conductivity Meter
• The ionic current depends on the total concentration of ions in
solution and on the length and area of the solution.
• Then multiplying the conductance by the cell constant corrects for
the effect of sensor geometry on the measurement.
• The result is the conductivity which depends only on the
concentration of ions.
• The cell constant is measured at the factory and the user enters the
value in the analyzer when the sensor is first put in service.

10. Contacting-type Conductivity Meter
• Some contacting sensors have four electrodes.
• In the four-electrode measurement, the analyzer injects an alternating
current through the outer electrodes.
• Measures the voltage across the inner electrodes.
• The analyzer calculates the conductance of the electrolyte solution
from the current and voltage.
• Two-electrode sensors are ideal for measuring high purity water in
semi-conductor, steam electric power, and pharmaceutical plants.

11. Inductive Conductivity Meter
• Inductive conductivity is sometimes called toroidal or
electrodeless conductivity.
• An inductive sensor consists of two wire-wound metal toroids
encased in a corrosion-resistant plastic body.
• One toroid is the drive coil, the other is the receive coil.
• The sensor is immersed in the conductive liquid. The analyzer
applies an alternating voltage to the drive coil, which induces a
voltage in the liquid surrounding the coil.

12. Inductive Conductivity Meter
• The voltage causes an ionic current to flow proportional to the
conductance of the liquid.
• The current in the receive coil depends on the number of windings in
the .
• The number of windings and the dimensions of the sensor are
described by the cell constant.
• As in the case of contacting sensors the product of the cell constant
and conductance is the conductivity.rive and receive coils.

14. Benefits of Inductive Conductivity Meter
• The toroids do not need to touch the sample.Thus, they can be
encased in plastic, allowing the sensor to be used in solutions that
would corrode metal electrode sensors.
• Inductive sensors tolerate high levels of fouling, they can be used
in solutions containing high levels of suspended solids.
• Inductive sensors are ideal for measuring solutions having high
conductivity.

15. Benefits of Inductive Conductivity Meter
• High conductivity solutions produce a large, easily measured
induced current in the receive coil.
• They can be cleaned with soap or solvents and a brush. There are
no electrodes so here is no possibility of their damage.
• Inductive sensors usually have a fairly large hole which permits
free flushing.

16. Drawbacks of Inductive Conductivity Meter
• They are restricted to samples having conductivity greater than
about 15 μS/cm. They cannot be used for measuring low
conductivity solutions.
• Calibration is awkward because clearance in the calibration baths
must be provided for the external field. Calibration is especially
inconvenient if the sensor is already mounted.
• Errors can come easily in the instrument.

17. Temperature Dependence
• The conductivity of a solution is highly temperature dependent therefore it
is important to either use a temperature compensated instrument.
• Calibrate the instrument at the same temperature as the solution being
measured.
• The conductivity of common electrolytes typically increases with
increasing temperature.
• Over a limited temperature range, the way temperature affects the
conductivity of a solution.

18. Calibration of Conductivity Meter
• Calibration leads to a more accurate reading.
• To calibrate a meter, follow the instructions for that meter in general.These
steps are easy and standardized.
• The meter usually has a menu item that allows you to enter the calibration
mode.
• Change the setting on the side that you can adjust with a small screwdriver
or tool.
• Place the probe in a solution with a known conductivity value and
temperature and set the meter to that conductivity.

19. Conductivity Meter Applications
• The instrument is used in concentration Measurement. This is the
simplest and one of the most widely used applications.
• Conductivity meters are also used in Leakage detection.
• Water used for cooling in heat exchangers and surface condensers.
• Heat exchangers contains large amounts of dissolved ionic solids.
• Leakage of the cooling water can result in potentially harmful
contamination.

20. Conductivity Meter Applications
• Used in Interface detection. If two liquids have appreciably different
conductivity, a conductivity sensor can detect the interface between them.
• In the pharmaceutical and food and beverage industries, piping and vessels
are periodically cleaned and sanitized in a procedure called clean-in-place.
• Conductivity is used to monitor both the concentration of the CIP solution,
typically sodium hydroxide, and the completeness of the rinse.
•