Digital Multimeter (DMM)


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INTRODUCTION:

The cathode-ray oscilloscope (CRO) is a common laboratory instrument that
provides accurate time and aplitude measurements of voltage signals over a wide range of frequencies. Its
reliability, stability, and ease of operation make it suitable as a general purpose laboratory instrument. The
heart of the CRO is a cathode-ray tube shown schematically in
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative
electrode) and accelerated toward the fluorescent screen. The assembly of the cathode, intensity grid,
focus grid, and accelerating anode (positive electrode) is called an electron gun. Its purpose is to generate
the electron beam and control its intensity and focus. Between the electron gun and the fluorescent screen
are two pair of metal plates - one oriented to provide horizontal deflection of the beam and one pair
oriented ot give vertical deflection to the beam. These plates are thus referred to as the horizontal and
vertical deflection plates. The combination of these two deflections allows the beam to reach any portion of
the fluorescent screen. Wherever the electron beam hits the screen, the phosphor is excited and light is
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emitted from that point. This conversion of electron energy into light allows us to write with points or lines
of light on an otherwise darkened screen.


PROCEDURE:

Set the signal generator to a frequency of 1000 cycles per second. Connect the output from the
generator to the vertical input of the oscilloscope. Establish a steady trace of this input signal on
the scope. Adjust (play with) all of the scope and signal generator controls until you become
familiar with the function of each.
II. Measurements of Voltage: By adjusting the Horizontal Sweep time/cm and trigger, a steady
trace of the sine wave may be displayed on the screen. The trace represents a plot of voltage vs.


FUNCTION GENERATOR:
A function generator is a device that can produce various patterns of voltage at a variety of frequencies
and amplitudes. It is used to test the response of circuits to common input signals.



Features and controls
Most function generators allow the user to choose the shape of the output from a small number of options.
• Square wave - The signal goes directly from high to low voltage.
• Sine wave - The signal curves like a sinusoid from high to low voltage.
• Triangle wave - The signal goes from high to low voltage at a fixed rate.
The amplitude control on a function generator varies the voltage difference between the high and
low voltage of the output signal.
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