1. The document discusses electrochemical sensors and their use in monitoring chloride ingress in concrete structures. It provides the allowed limits of chloride in concrete and steel. 2. It describes how a sensor was used to predict problems at one site and found another site's concrete to be good. It also discusses potentiometric, amperometric, and ChemFET sensors. 3. Various applications of electrochemical sensors are mentioned like medical testing, environmental monitoring, and process control industries. The Nernst equation relating sensor output and reaction conditions is also summarized.

1. By-
M.MUHURTH
CIVIL ‘A’ SECTION
ROLL NO-41

2. ELECTROCHEMICAL
SENSORS IN
MONITORING CHLORIDE
INGRESS IN CONCRETE
STRUCTURES

4.  ALLOWED LIMIT IN CONCRETE
 0.05 %wt. (by mass of concrete)
 0.4 %wt. (by mass of cement)− 0.85 g of salt (max)
allowed in 1 L (or 1.7 kg) of concreteor 1.89 lb/cu.
yd.
 ALLOWED LIMIT IN STEEL
 Steel corrodes when the chloride content is 0.6 times
the concentration of [OH¯ ]
 If the pH = 12.9, [OH¯ ] = 1x10-1.1 M; and [Cl¯ ]
= 48 mM

7. THE SENSOR PREDICTED
-problems at site #1
-found site#2 concrete was good

8. 1. ELECTRICALS IN CHLORIDE INGRESS
IN MONITORING OF CONCRETE
STRUCTURES
2. SWEAT SENSING BELT

13. 1.Detection of cystic fibrosis
 Clinical interest in sweat electrolyte analysis
includes the diagnosis of Cystic Fibrosis
(CF),indicated by abnormally high sodium levels
in sweat
2.Dehydration monitoring in
athletes
 More the dehydration more will be the concentration of
sodium therefore more will be the output from the
sensor hence indicating the level of dehydration

14. Electrochemical sensors for clinical
analysis

16.  In potentiometric sensors, the potential
difference between the reference electrode
and the indicator electrode is measured
without polarizing the electrochemical cell
Amperometric electrochemical sensors
 Amperometry is a method of electrochemical
analysis in which the signal of interest is a
current that is linearly dependent upon the
concentration of the analyte

17.  ChemFET, or chemical field-effect transistor,[1] is a
type of a field-effect transistor acting as a
electrochemical sensor. It is a structural analog of
a MOSFET transistor, where the charge on the gate
electrode is applied by a chemical process. It may be
used to detect atoms, molecules, and ions in liquids
and gases.
 Its detection principle is based on the production of
acidic or basic chemical species due to the urease
enzymatic reaction.
 There will be a ph sensor associated with the
chemFET according to the concentrations of ph the
signal is generated in the transistor based on the
standard concentrations the urea can be detected in
the blood sample

19. 1.ENVIRONMENTAL HEALTH MONITORING
USING ELECTROCHEMICAL GAS SENSORS

20.  Gas sensor is a subclass of chemical
sensors.
 Gas sensor measures the concentration of
gas in its vicinity. Gas sensor interacts
with a gas to measure its concentration.
Each gas has a unique breakdown voltage
i.e. the electric field at which it is
ionized. Sensor identifies gases by
measuring these voltages. The
concentration of the gas can be
determined by measuring the current
discharge in the device

21.  Process control industries
 Environmental monitoring
 Boiler control
 Fire detection
 Alcohol breath tests
 Detection of harmful gases in mines
 Home safety
 Grading of agro-products like coffee and spices

22.  I = F × (A/σ) × D × C × n
 where:
I: Sensor output
F: Faraday constant= = 9.648 70 x 104,
coulombs/faraday(C mol-1).
A: Surface area of diffusion film
σ：Thickness of diffusion film
D: Gas diffusion coefficient
C: Gas concentration
n: Number of reaction electrons
 The linear relationship of gas concentration to
sensor output makes this technology ideal for gas
sensing applications.

23.  Bulky
 Consume lots of power
 Require “risky” high voltage to operate.
DEVELOPMENT
 There is a recent progress in developing MEMS (Micro-Electro-
Mechanical Systems) based H2 gas sensors. These sensors
couple novel thin films as the active layer with a MEMS
structure known as a Micro-Hotplate. This coupling results in
a H2 gas sensor that has several unique advantages in terms
of speed, sensitivity, stability and amenability to large scale
manufacture. Preliminary results are extremely encouraging
and suggest that this technology has substantial potential for
meeting the sensing requirements of a hydrogen based
energy economy.

24.  the Nernst equation is an equation that relates
the reduction potential of a half cell (or the
total voltage, i.e. the electromotive force, of the fuel
cell) at any point in time to the standard electrode
potential, temperature, activity, and reaction
qoutient of the underlying reactions and species used.
 Ecell = E0
cell - (RT/nF)lnQEcell = cell potential
under nonstandard conditions (V)
E0
cell = cell potential under standard conditions
R = gas constant, which is 8.31 (volt-
coulomb)/(mol-K)
T = temperature (K)
n = number of moles of electrons exchanged in
the electrochemical reaction

25.  electrochemical sensors are widely used in
all the branches of science
 Chloride threshold sensors helps in
monitoring of the structures and hence
predicting the life of the structures
 They are also helpful in monitoring the
human body and hence it is important in
medical sciences
 They are also helpful in monitoring our
environment
 Thus electochemical sensors are the chief
aspect in various fields mainly in health
monitoring related to various apects

26.  IEEE EXPLORER
 .E. J. Gannon and P.D. Cady, Condition Evaluation of Concrete
Bridges Relative to Reinforcement Corrosion, Vol. 1: State ofthe
Art of Existing Methods, Publication No. SHRP-S/FR-92-103,
Strategic Highway Research Program, Washington, D.C.(1992).
@J. Kumar and P. and Chambon, "the estrogen receptor binds tightly
toits responsive element as a ligand induced homodimer,"
cel1,vol. 55,pp. 1456, 1988
> @. Mueller-Fahmow and A. U. Enger, "Ligand binding domain of
estrogen
receptors," current opinion in biotechnology, vol. 10, pp. 550-
556,1999
> @. J. Oosterkamp, B. Hock, M. Seilkrt, and H. Irth, "Novel
monitoring
strategies for xenoestrogens," True-Trends in Anu[i>ticuI
Clzernistty, vol. 1