[rosy]

Omid, this forum is not intended to do your homework for you. This is something of a recurring theme in your posts. Any forum post will, and should, be taken as a basis for a discussion of interesting related scientific points, getting stroppy because no-one has given you the answer that will enable you to gain credit on your assignment won't gain you either friends or answers.

[omid (OP)]

bored chemist,
this is what i submitted to my teacher and i got the grade, probably this was anaswer to my question;

oscilloscope Can be used as troubleshooting device, to search for source of problem so that it can be rectified. Can be used to check if newly designed circuit are safe; newly designed circuit might malfunction because of bad voltage level, electrical noise or design error.  Since oscilloscope is a good voltmeter- the input resistance of the device is very high so that very little current is taken from the circuit either in AC or DC current. Digital electronics usually operate from a clock, so a dual-trace scope which shows both the clock signal and a test signal dependent upon the clock is useful. Storage scopes are helpful for capturing rare electronic events that cause defective operation.

Oscilloscope can also be used a alarm or indicator in circuits. E.g. when a.c current is too, the oscilloscope can alert, that the current and needs to be lowered to the standard that’s suitable.

Oscilloscopes that are rated for high-power applications can monitor and/or display currents and voltages associated with electrical power or high-power switching.

One of the advantages of a scope is that it can graphically show signals: where a voltmeter may show a totally unexpected voltage, a scope may reveal that the circuit is oscillating. In other cases the precise shape or timing of a pulse is important.

In a piece of electronic equipment, for example, the connections between stages e.g. electronic mixers, electronic oscillators, amplifiers may be 'probed' for the expected signal, using the scope as a simple signal tracer. If the expected signal is absent or incorrect, some preceding stage of the electronics is not operating correctly.

Once the faulty stage is found, further probing can usually tell a skilled technician exactly which component has failed. This sort of troubleshooting is typical of radio and TV receivers, as well as audio amplifiers, but can apply to quite-different devices such as electronic motor drives.

[lyner]

The term "safety device" is not really appropriate here. An oscilloscope is an "Analytical Tool" which can be used to asses safety issues - it isn't a safety device any more than you could say a hammer or a screwdriver could be.

[syhprum]

As a 'skilled technician' I have used my oscilloscope many times to investigate abnormal circuit operation but safety has seldom been a consideration.
There are many better ways to investigate safety considerations.