Vertical deflection system: * The function of the deflection system provides an amplified signal of the proper level to derive the vertical deflection.

Vertical deflection systemVertical deflection system::

*The function of the deflection system provides an amplified signal of the proper level to derive the vertical deflection plates

without distorting the signal

* A general type oscilloscope can accept as

low as a few millivolts/cm of

deflection up to hundreds of volts using the built in attenuator and external

probes.

Here ,the attenuator sets the sensitivity of

oscilloscope in the common sequence

(1-2-5)

* Types of attenuators ::

This type of attenuators (resistive divider att.)

is connected to an amplifier with 10PF input capacitors

the impedance changes based on the setting of attenuator ,,therefore, the RC time constant and thus the frequency

response of the amplifier are depending on the setting of the attenuator,

Note: this type of attenuator is needed to provide measurements of DC signal that are maybe viewed in the

presence of the high DC voltage

In the base of the probe at the oscilloscope connector, there is an adjustable capacitor. This capacitor is adjusted so that the ratio of the shunt capacitance to the series capacitance is exactly 10 to 1.

The attenuator probe (usually called 10-1 probe) provides approximately a 10-1 reduction in the input capacitance. If the setting of the compensation is incorrect, then the result will be seen by observing the rise-time-pulse.

H.D

Most Oscilloscopes have a built in oscillator to trigger the beam when no input signal is present , so that one would know the base time,,

Some oscilloscopes have two time base generator where one would trigger before the other

This advantage is applied

in a situation where a signal with longer period is begun viewed but a small part of the signal is to be analyzed …

The sweep does not usually trigger for each cycle of the vertical input unless the sweep pulse roll off time is less than +ve period of the input …

Oscilloscope Probes

Current Probe :

The current sensor consists of a conventional transformer and a Hall-effect device.

Alternating current in the wire will induce voltage in the secondary winding by the transformer , any direct current

will not appear at the current transformer secondary circuit, the direct current

passing through the wire will cause the magnetic flux in the core to increase will

effect the permeability of the material used for the core (this is undesirable)

A feedback system is arranged with an amplifier such that any magnetic field

present in the Hall-effect device will cause the current to be induced in to the

secondary winding to counteract the magnetic field induced in the wire

being used in measurement .

: Frequency determination

To display the carrier the oscilloscope must be capable of covering the carrier frequency of the transmitter the horizontal sweep has only to cover the modulation frequency.

The modulation percentage The modulation percentage can be determined from the can be determined from the wave form & is calculated aswave form & is calculated as::