SENSORY MEASUREMENT

SENSORY
MEASUREMENT
MUKESH . S
AGENDA:
 Electro
Oculo Graph.
 Electro Retino Graph.
 Electro Gastro Graph.
 Galvanic Skin Resistance.
 Audiometer-Pure tone, Speech
EYE
EYE LAYERS:
ELECTRO-OCULOGRAM.

Electrooculography (EOG) is a new technology of
placing electrodes on user's forehead around the
eyes to record eye movements . This technology is
based on the principle of recording the
polarization potential or corneal-retinal potential
(CRP), which is the resting potential between the
cornea and the retina. This potential is commonly
known as electro-oculo gram. (EOG) is a very small
electrical potential that can be detected using
electrodes. The EOG ranges from 0.05 to 3.5 mV in
humans and is linearly proportional to eye
displacement.
Electrode placements for EOG
detection
POENTIAL POINTS
Fig. 28.7 The two-dimensional model depicting the ERG source and volume conductor
inhomogeneities.
The retina and R-membrane impedance are represented together by double layer and RR and
RC, respectively. The other parameters correspond to the conductivities and are listed in
Table 28.1.
Cont..
EOG is a bio-electrical skin
potential measured around the eyes.
 the amplitude is relatively the same (15200uV).
 generates voltage up to 16uV and 14uV
per 1° in horizontal and vertical way.
 Basically
Electro-Retino Graph.




It is clinically recorded with a specially constructed
contact lens that carries a chlorided silver wire.
The electrode, which may include a cup that is filled
with saline, is placed on the cornea. The reference
electrode is usually placed on the forehead, temple,
or earlobe.
The amplitude depends on the stimulating and
physiological conditions, but ranges in the tenths of a
millivolt.
The sources of the ERG arise in various layers of the
retina,
The recording electrodes are at the surface of this
region. initiated by a brief light flash stimulus to the
photoreceptors
Applications…..
Normalized values of volume conductor parameters of the model of the eye
Parameter
Structure
Value in model
Dimension
σ1
Aqueous & Vitreous
1.0
57 [S/cm]
σ2
Sclera
0.01 ... 0.15
57 [S/cm]
σ3
Extraocular
0.0005 ... 0.06
57 [S/cm]
σ4
Lens
0.08 ... 0.3
57 [S/cm]
σ5
Cornea
0.03 ... 0.86
57 [S/cm]
σ6
Air
0.0
57 [S/cm]
RR
R-membrane resistinv.
1.67 ... 6.25
1/57 [Ω/cm²]
RC
1/(2πCs)
27.8 ... 58.8
1/57 [Ω/cm²]
RXC
Capacitive reactance
RC/frequency
ERG ELECTRODES:
Clinical applications…..
MORE DETAILS:
 http://webvision.med.utah.edu/book/ele
ctrophysiology/the-electroretinogramclinical-applications/
Electro Gastro Graph:
An electrogastrogram (EGG) is a graphic produced
by an electrogastrograph, which records the
electrical signals that travel through
the stomach muscles and control the muscles'
contractions.
An electrogastroenterogram (or gastroenterogram) is
a similar procedure, which writes down electric
signals not only from the stomach, but also
fromintestines.
 An electrogastrogram and a gastroenterogram
are similar in principle to
an electrocardiogram (ECG) in that sensors on the
skin detect electrical signals indicative of muscular
activity within. Where the electrocardiogram
detects muscular activity in various regions of the
heart, the electrogastrogram detects the wave-like
contractions of the stomach
Galvanic Skin Resistance:

Skin conductance, also known as galvanic
skin response (GSR), electrodermal response
(EDR), psychogalvanic reflex (PGR), skin
conductance response (SCR) or skin
conductance level (SCL), is a method of
measuring the electrical conductance of the
skin, which varies with its moisture level. This is
of interest because the sweat glands are
controlled by the sympathetic nervous
system,[1] so skin conductance is used as an
indication of psychological or physiological
arousal. There has been a long history of
electrodermal activity research, most of it
dealing with spontaneous fluctuations or
reactions to stimuli.
Galvanic Skin Response Circuit
GSR SCHEMATIC:
Applications….
Audiometry
Audiometry (from the Latin audīre, "to hear" and
metria, “to measure”) is the science of
measuring hearing acuity for variations in sound
intensity and pitch and for tonal purity, involving
thresholds and differing frequencies.
Typically, audiometric tests determine a
subject's hearing levels with the help of an
audiometer. Results of audiometric tests are
used to diagnose hearing loss or diseases of the
ear, and often make use of an Audiogram.
Audiogram


An audiogram is a graph that shows the
audible threshold for standardized
frequencies as measured by an audiometer.
The Y axis represents intensity measured in
decibels and the X axis represents frequency
measured in Hertz.
Most audiograms cover a limited range of
frequencies 100 Hz to 8000 Hz (8 kHz) because
this range includes the fundamental
frequency of sounds in speech
Graph:
Types:
Subjective Audiometry
 1. Pure tone audiometry
 2. Speech audiometry
 3. Bekesy audiometry
Objective Audiometry
 4. Acoustic impedance audiometry/
Tympanometry
 5. Evoked response audiometry
Pure tone audiometry
 Pure
tone audiometry (PTA) is the key
hearing test used to identify hearing
threshold levels of an individual, enabling
determination of the degree, type and
configuration of a hearing loss
YOUR TURN….
 Explain
the entire details in audio metery
Experiment…

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