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ELECTRICAL MEASUREMENT LAB
Department of Electrical Engineering
Supervisor
Submitted by
Dr. Girish Parmar
Control & Instrumentation
(Associate Professor)
Department of Electronics Engineering
University College of Engineering,
Rajasthan Technical University, Kota
February, 2015
Experiment No.: 1
OBJECT: To study of about the CRO (Cathode Ray Oscilloscope) and digital CRO, CRO probes.
THEORY:
The cathode ray oscilloscope is an externally useful important used for studying wave shops of
alternatively current and voltage as well as for measurement of voltage current. Power and frequency
infect almost any quantity that involves amplitude of electrical signal as the function of time on the
screen.
BLOCK DIAGRAME:
Fig. 1.1 Blok Diagram Of CRO
The instrumental employs cathode ray tube. If generates electron beam accelerates the beam to high
velocity. Deflects the beam to create the image and contain a phosphor screen where the electron beam
eventually becomes visible for accomplishing this task various electrical signal and voltages are required
which are provided by the power supply cut of the oscilloscope.
Low voltage supply is required for the heater of electron gun and high voltage of the order
of few thousand volts is required for the cathode ray tube to accelerate the beam. Normal supply of few
hundred volts is required for the other circuit of the oscilloscope. Horizontal & vertical reflection plates
are fitted b/w electron gun and screen to deflected beam strikes the screen and creates a visible spot.
This spot is deflected on the screen in horizontal direction (x-axis) with constant time dependant rate.
FEATURES & USES:
1. Exterior: A typical oscilloscope is box shaped with display screen numerous input connectors and
control knobs and buttons on the front panel
2. Inputs: The signal to be measured is fed to are of the input connection screen as Bmc or N- tube. If
signal source has its own coaxial connector then a simple coaxial cone isled.
3. The Trace: The oscilloscope repeatedly draws a horizontal time called trace across the middle. If the
screen from left to right are of the control. The time base control sets the speed at which the time is
drawn and is calibrated in the seconds per division. If the voltage deposits from zero the trace is
deflected either upwards or downwards.
4. Trigger: To provide more stable trace modern oscilloscope have a function called Trigger. The effect is
to resynchronize the time base to the input signal preventing horizontal any of the trace. In this way
triggers allows. The display of provider signals such as sine waves and square waves.
CRO PROBES: A probe is physical device used to connected electronic test equipment to the device
under test. A probe is more than a cable with clip on tip. It is a high quality connector designed not to
pick up slay ratio and power line noise.
Describe as three probes as follows:1. Direct probes (N): This is simplest probe. If avoid stray pickups which may cause troubles in
measurement of low level signals.
2. Isolation Probes: Such a probe is employed to avoid the undesirable circuit loading effects of the
shielded probes isolation probe is made by placing a carbon resistor in series with the test load.
3. Passive probes: A passive box probes. Notice the suited in the probe needle that allows choosing
between 1x or 10 x. passive probes usually connected to the loading of about 10-15 p.f. and 10 m if a
ohm.
4. Zd Probes: Zd probes are specialized type of low capacitance passive probes used in low impedance
very high frequency circuits very similar to designed to ordinary passive probes.
5. Active Probes: Active scope probes are a small usually FET based amplifier mounted directly with in
the probe head. By doing this, they are able to obtain exceptionally low passive capacitance and high DC
resistance.
RESULT : We have studied about the CRO, digital CRO and CRO probes.