Informative Presentation on Conductivity Meter By Atif Nauman (University of Gujrat)

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.
•