Scopes An oscilloscope is a visual voltmeter An

Scopes ®An oscilloscope is a visual voltmeter. ®An oscilloscope converts electrical signals into a visual image representing voltage changes over a specific period of time.

Scopes ® The information is is displayed in the form of a continuous voltage line called a waveform pattern or trace. ® An oscilloscope screen is a cathode ray tube (CRT), which is very similar to the picture tube in a television set.

Scopes ® An upward movement of the voltage trace on an oscilloscope screen indicates an increase in voltage, and a downward movement of this trace represents a decrease in voltage. ® The size and clarity of the displayed waveform is dependent on the voltage scale and the time reference selected by the technician.

Scopes ® Dual-trace oscilloscopes can display two different waveform patterns at the same time. ® The screen of a lab scope is divided into small divisions of time and voltage. ® These divisions set up a grid pattern on the screen.

Scopes ® Time is represented by the horizontal movement of the waveform. ® Voltage is measured with the vertical position of the waveform. ® The scope displays voltage over time. ® The waveform moves from the left to the right. ® The value of the divisions can be adjusted to improve the view of the voltage waveform.

Scopes ® The scope display is divided into small sections. A series of grids, or graticules divide the display. ® The voltage level between grids is adjustable ® e. g. - If the signal ranged between zero and one volt, five volts per division would be too high.

Analog vs Digital Scopes ® Analog scopes show the actual activity of a circuit and are called real-time scopes. ® A digital scope, (DSO) digital storage oscilloscope, converts the voltage signal into digital information and stores it in its memory. ® A technician can freeze the captured signal for close analysis.

Scopes ® Both an analog and a digital scope can be dual-trace scopes. ® By watching two traces simultaneously, you can watch the cause and effect of a sensor, as well as compare a good or normal waveform to the one being displayed.

Waveforms ®A waveform represents voltage over time. ® When the trace is a straight horizontal line, the voltage is constant. ® A diagonal line up or down represents an increase or decrease in voltage. ® Scopes can display AC or DC voltage, either one at a time or both at the same time.

Waveforms ®A normal AC signal changes its polarity and amplitude over a period of time. ® The waveform created by AC voltage is called a sine wave. ® One complete sine wave shows the voltage moving from zero to its positive peak, then moving down through zero to its negative peak and returning to zero. ® One complete sine wave is a cycle.

Waveforms ®A complete cycle is the amount of time a signal takes before it begins to repeat itself. ® The number of cycles that occur per second is the frequency of the signal. ® Square waves are identified by having straight vertical sides and a flat top. ® This type of wave represents voltage being applied, voltage being maintained, and no voltage applied.

Pulse Train ®A pulse train is any electrical signal that turns on and off, or goes high and low, in a series of pulses. ® Pulse train signals can vary in three ways.

Frequency ® Frequency is the number of cycles that take place per second. ® The more cycles that take place in one second, the higher the frequency reading. ® Frequencies are measured in Hertz, which is the number of cycles per second. ® An eight Hertz signal cycles eight times per second.

Duty Cycle ® Duty cycle is a measurement comparing the signal on-time to the length of one complete cycle. ® Duty cycle is measured in percentage of on-time. ® A 60% duty cycle is a signal that’s on 60% of the time, and off 40% of the time. ® Dwell is another way of measuring duty cycle. Measured in degrees instead of percent.

Pulse Width ® Pulse width is the actual on time of a signal, measured in milliseconds. ® With pulse width measurements, offtime doesn’t really matter - the only real concern is how long the signal’s on. ® In automotive applications, the only type of signal we measure signal pulse width is electronic fuel injectors.

E. G. - ABS brake sensor ® ® ® With the pickup disconnected: Connect one probe to one of the leads from the coil, and the other probe to the other lead. Voltage scale: 200 m. VAC Time Base: 5 ms - up, depending on speed Trigger: Level: zero volts Slope: positive The wheels must turn for the ABS sensors to produce a waveform. Signal frequency increases with vehicle speed.

Pronoun and Antecedent Agreement ® in person The resident made her feelings known. ® Agreement in number The residents made their feelings known. ® The board of directors gave its approval. (the board acted as a single unit. ) ® Some of the creditors have expressed concern ® Some of the gasoline has water in it. ® ® Agreement ® in gender A manager must use his or her judgment.

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