Year 2 E3 Flashcards
The heart of an oscilloscope is
a special vacuum tube called the cathode-ray tube (CRT)
CRT consists of four main parts
electron gun
vertical-deflection plates
horizontal-deflection plates
fluorescent screen
Screen of the CRT
is coated on the inside with phosphor
which has the property of phosphorescence.
what is the grid system on the fluorescent screen called
graticule
Horizontal axis
is the line along which the time of the wave is measured
Vertical axis
magnitude or amplitude of the voltage is measured
Define Sweep
horizontal movement of the electron beam
Define Sweep time
is the time taken for the trace to travel across 1 cm of the screen
Define level
point on the input signal wave where the trace starts.
Define channel
is the input terminal of the incoming vertical signal
Define Probes
are used to make the electrical connection from the scope to the circuit under test
two types of probe are used: time 1 and times 10
Define Astigmatism
to adjust the roundness of the beam spot
Define amplitude
volts/div allows a distance of 1 cm vertically to represent an input from 10mV to 50V
DC/AC ground coupling switch
DC direct coupling
AC alternate coupling
GND ground
Chop/alternate control
ADD sum of ch 1 and ch2
ALT displays each channel alternately
CHOP switches between ch1 and ch2
Sweep speed
time/div or sec/div: determine the rate at which the beam sweeps across the screen
Oscilloscope calibration
Uses the PROBE ADJUST terminal
sends a square-wave voltage of 50mV peak to peak and Hz of 1 kHz
Probe calibration
X10 probes has a voltage-dividing circuit in its body. Sometime need adjustment this is referred to as probe compensation
Probe multipliers
x1 probe impedance of 1 Megohm
x10 probe impedance of 10 Megohs this decreases the value of input voltage by 1/10
Shorts due to probe connection
if the ground side is unknown, do not connect the ground clip of the probe.
Use of isolation transformer
reduces the change of short
must use ground lead
Using two probes
when using two probes for simultaneous voltage measurements use only one ground clip
