Transcript 23-delay line

DELAY TIME
In many pulse circuit applications, it is
necessary to delay a signal a certain
amount of time called delay time.
Delay circuits may be classified in two
main groups: electronic circuits(e.g
mono stable multi vibrator and
blocking oscillator elc.)and
electromagnetic delay lines.
• The electronic circuits operate on the principle of
being in a stable until triggered by a pulse. Then
they shift to a quasi stable state for a period of
time determined usually by the constant or RC
circuit. After this period of time, the circuit
returns against to its stable state until triggered
again by another pulse. If some means is provided
to have a pulse generated at a time the circuit
returns to its stable state, a time delay circuit
results. The output pulse is not necessarily an
exact reproduction of the input pulse. Its
amplitude and width are dependent upon the
circuit producing it and not on the amplitude and
width of the input pulse.
Types of delay lines
• Electronic types
• electromagnetic type
Electromagnetic delay lines
• Electromagnetic delay lines may be further
classified as distributed parameter or lumped
parameter delay lines. The distributed parameter
line more closely approaches a transmission line,
whereas the lumped parameter line resembles a
filter. Delay ranging from a few nanoseconds to
hundreds of micro-seconds are obtainable with
electromagnetic lines. For longer delays acoustic
delay lines and storage devices are used. Acoustic
delay lines employ acoustic wave propagation
and electro-mechanical transducers at the input
and output.
Lumped parameter delay lines
• Consists of a number of inductors and
capacitors , the inductors are connected in
series and the capacitors are through the
junction between the inductors to the ground
.
Distributed Parameter Delay lines
• Normally all transmission lines consists of pair
of straight conducting wires or coaxial cables.
ELECTRONIC DELAY LINE
• Electronic delay line is an electronic circuit used
to delay a pulse waveform ,Any monostable
circuit may be used for this purpose. the input
pulse is used to trigger the monostable circuit,
the output is generated by the monostable circuit
itself
• The amplitude and duration Tp of the output
pulse is controlled by the monostable circuits .
• Hence,a monostable circuit can be used as pulse
delay device as well as pulse reshaping device.
monostable multivibrator
• monostable multivibrator is an electronic
circuit that generates an output pulse. When
triggered, a pulse of pre-defined duration is
produced. The circuit then returns to its
quiescent state and produces no more output
until triggered again.
Monostable multivibrator as atime
delay device
• The most popularly used circuit as an
electronic delay line is the monostable
multivibrator .
• The monostable multivibrator should be
triggered by the negative going edge of the
input pulse.
• The normally ON transistor at the same time
voltage at Vo changes from Vce ON to Vcc it
stay at Vcc depends upon the time constant
C1R1.if pulse width time tp1 become equal to
tp2 and amplitude of both input and output
pulses also become equal then the pulse
become delay by (one bit time) time tp
Uses of delay lines
• Delay line are used in distributed amplifiers
cathode ray oscilloscope pulse coder and
decoder ,measuring instrument ,radar , TV
system and computers.
CATHODE RAY OSCILLOSCOPE
• CRO is an extremely useful and versatile
laboratory instrument used for the
measurement and analysis of waveforms and
other phenoena in electronic circuits.
major subsystem of a general purpose
CRO consists of the following
• 1. Cathode ray tube
• 2. Vertical amplifier
• 3. Delay line:this circuit is used to, delay the signal for a period of time in
the vertical section of CRT
• 4. Time base circuit
• 5. Horizontal amplifier
• 6. Trigger circuit
• 7. Power supply.
FUNCTION OF DELAY LINE
• The diagram shows that when the delay line is
not used, the initial part of the signal is lost
and only part of the signal is displayed.
DUAL TRACE CRO
• Two different input signals are used is Channels A &
B with attenuators and preamplifiers.A delay line is
used between electronic switch & vertical amplifier
that alternately connects the input to main vertical
amplifiers.
.There are two common operating
mode for electronic switch called as
• 1. Alternate mode
• In this mode , the CRO spot traces channel A signal on one sweep &
channel B on next . These signals have calibrated input attenuators
and vertical position control and also amplitude of these signals can
be adjusted individually and two images are placed separately on
the screen.
• 2. Chop mode
• This mode is used for higher frequencies say of order 100kHz
•THE END