Measurement and Multisim Simulation of volt ampere characteristics of circuit components (engineering documents attached)

Catalog

2.1  The experiment purpose

2.2  Experimental principle

2.3  Experiment content and steps

 2.4  Experimental requirements and precautions

2.5  Experimental report and thinking questions

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2.1  The experiment purpose

1. Master linear resistance 、 Measurement method of volt ampere characteristics of nonlinear resistance elements ;

2. Master the selection of measuring points and the method of drawing curves in voltammetry ;

3. Learn how to use direct reading instruments, DC regulated power supplies and other equipment .

2.2  Experimental principle

The characteristics of circuit components can generally be measured by the terminal voltage on the component U As a function of the current passing through the element I=f（U） To express , The box I-U A curve on the plane , This curve is called the volt ampere characteristic curve of the element . Resistive elements are the most common elements in circuits , There are linear resistance and nonlinear resistance . The actual circuit is rarely composed of only power supply and linear resistance “ Level shift ” circuit . However, nonlinear devices are often widely used , For example, nonlinear element diode has single conductivity , It can convert AC signal into direct flow , It plays a rectification role in the circuit .

The ohm block of the multimeter can only be in a specific U and I Measure the corresponding resistance value , Therefore, the volt ampere characteristics of nonlinear resistors cannot be measured . Generally, the circuit with source “ On-line ” The current value corresponding to the terminal voltage of the measuring element in the state , Then from the formula R=U/I To find the resistance value .

1. The volt ampere characteristics of linear resistance elements conform to Ohm's law U=RI, Its resistance value does not change with the change of voltage or current value , The volt ampere characteristic curve is a straight line passing through the coordinate origin , Pictured 2-1（a） Shown , The slope of the line is equal to the resistance value of the resistor .

2. Incandescent lamp can be regarded as a kind of resistance element , The filament resistance increases with the increase of temperature , General bulb “ Cold resistance ” And “ Thermal resistance ” The resistance value of can differ by several times , The greater the current through the incandescent lamp , The higher the temperature , The greater the resistance , That is, for a group of transformed voltage values and corresponding current values , income U/I Not a constant , So its volt ampere characteristic is nonlinear , Pictured 2-1（b） Shown .

2. Ordinary semiconductor diode is also a kind of nonlinear resistance element , Its volt ampere characteristics are shown in the figure 2-1（c） Shown . The resistance of the diode varies with the voltage or current , Change with the change of direction . Its forward pressure drop is very small （ Generally, germanium tube is about 0.2-0.3V, The silicon tube is about 0.5~0.7V）, The forward current rises sharply with the increase of forward voltage drop , When the reverse voltage increases from zero to more than ten to dozens of volts , Its reverse current increases very little , Roughly regarded as zero . The forward voltage of LED is 0.5-2.5V Between time , The forward current varies greatly . Visible diode has single conductivity , But the reverse voltage is too high , Exceed the limit value of the pipe , It will cause tube breakdown and damage .

4. Zener diode is a special semiconductor diode , Its forward characteristic is similar to that of ordinary diodes , But its reverse characteristic is special , Pictured 2-1（d） Shown . When applying reverse voltage to the zener diode , Its reverse current is almost zero , But when the voltage increases to a certain value , The current will suddenly increase , In the future, its terminal voltage will remain constant , No longer increases with the increase of the applied reverse voltage , This is the reverse voltage stabilizing characteristic of the zener diode . In actual circuits , You can use regulators with different voltage stabilization values to achieve voltage stabilization .

chart 2-1  Volt ampere characteristic curve of linear resistance and nonlinear resistance

Point by point test method is usually used to draw volt ampere characteristic curve , Resistive elements have different terminal voltages U Under action , Measure the corresponding current I, Then draw the volt ampere characteristic curve point by point I=f(U), According to the volt ampere characteristic curve, the resistance value of the resistance element can be calculated .

2.3  Experiment content and steps

1. Measure the volt ampere characteristics of linear resistance

（1） According to the plan 2-2 Circuit shown , Select component , Combined with DC regulated power supply , Build the experimental circuit ;

（2） chart 2-2 in , Use current limiting resistor R by 300 o ,R1 The resistance can be set to 100, Ammeter positive pole and resistance R Connected to a , Negative electrode and resistance R1 Connected to a , Connect the ammeter in series with the circuit ,R1 The other end of the ground （GND） Connected to a , Voltmeter and R1 Parallel access circuit .

（3） Set the output of DC regulated power supply to 2.5V.

（4） Connect the power supply , Use a DC voltmeter to measure the output of the stabilized voltage source , Then connect the output of the stabilized voltage source to the figure 2-2 circuit .

（5） Slowly adjust the output voltage of the regulated power supply U, from 2.5V Start to slowly increase , No more than 5V. In the table 2-1 Record the readings of the corresponding voltmeter and ammeter . Be careful ： Ensure the multimeter when measuring voltage 1 In current measuring state .

（6） By formula U1/I Calculate the resistance value R′ Value , And included in the table 2-1 in , Compare with the actual measured value .

chart 2-2  Measurement of volt ampere characteristics of components

surface 2-1  Measure the volt ampere characteristics of linear resistance

U（V）	2.5	3	3.5	4	4.5	5
U 1（V））	0.625	0.75	0.875	1	1.125	1.25
I(mA)	6.25	7.5	8.75	10	11.25	12.5
R’（KΩ）	0.1	0.1	0.1	0.1	0.1	0.1

2. Measure the volt ampere characteristics of semiconductor diodes

（1） According to the figure 2-2, Put the resistance R1 Replace with semiconductor diode 1N4148, First measure the forward characteristic of the diode , namely 1N4148 The positive pole of the is connected with the negative pole of the ammeter ,1N4148 Negative pole and ground （GND） Connected to a , The forward pressure drop can be in 0～0.75V Between .

         After the above wiring is connected , Turn on the power , By table 2-2 Give different R, Record the measured voltage and current in the table 2-2 in , In the table UZ+ Is the voltage at both ends of the diode .

surface 2-2  Measurement of diode forward characteristic

R	100	150	300	500	600	1k	5.1k	100k
UZ+（V）	0.498	0.497	0.494	0.491	0.49	0.486	0.466	0.413
I(mA)	0.023	0.022	0.02	0.018	0.017	0.014	0.0067	0.0008

（2） When doing the reverse characteristic experiment , Diode 1N4148 Reverse connection , Its reverse voltage can be in 1-5V Between , At this time, there is no need for partial pressure , Directly provided by the stabilized voltage source . The measured data is included in the table 2-3 in .

surface 2-3  Measurement of diode reverse characteristic

UZ-（V）	1	3	4	5
I(uA)	0	0.4	0	0

 2.4  Experimental requirements and precautions

1. When measuring , The output voltage of the adjustable DC regulated power supply is controlled by 0 Slowly and gradually increase , Always pay attention to voltmeter and ammeter , Do not exceed the specified value .

2. Do not short circuit the output end of the DC regulated power supply .

3. Measuring , Always pay attention to the reading of ammeter , Change the range of ammeter in time , Do not make the instrument over range , Pay attention to the positive and negative polarity of the instrument .

2.5  Experimental report and thinking questions

1． According to the experimental data , Draw the volt ampere characteristic curve of each resistance on the square paper （ Among them, diode and regulator are positive 、 Reverse characteristics are required to be drawn in the same figure , just 、 The reverse voltage can be taken to different scales ）.

Its volt ampere characteristic curve is as follows ：

2． According to the volt ampere characteristic curve of linear resistance , Calculate its resistance , And compare with the actual resistance value .

The calculated resistance is the same as the actual resistance .

3． Summarize the results of this experiment .

Through this study, I have a further understanding of the volt ampere characteristics of linear resistance and nonlinear resistance . Through experiments, I have an intuitive understanding of the characteristics of diodes , in addition to , I also understand the working principle of Zener diode . Let me consolidate and further master the knowledge of circuit and circuit experiment .

4． Thinking questions ：

（1） What is the difference between the volt ampere characteristics of linear resistance and nonlinear resistance ？ Their resistance value is related to the current passing ？

answer ： The volt ampere characteristic of linear resistance is a straight line , Voltage is proportional to current , The resistance value will not change . The resistance value is independent of the current passing . The volt ampere characteristic curve of nonlinear resistance is a curve . Resistance is the property of conductor itself , It is nonlinear because the resistance value will change with temperature 、 Light and other factors affect , It has nothing to do with the current , It is the extension of power on time that causes the temperature on the wire to rise , Further lead to resistance changes .

（2） If the functional expression of the volt ampere characteristic of the element is I=f(u), When describing the characteristic curve , How should its coordinate variables be placed ？

answer ： In a general way , The horizontal axis is current , The vertical axis is voltage . There are also those that take the voltage as the horizontal axis , For example, the volt ampere characteristic curve of diode .

Beginner circuit analysis , There may be mistakes , Also ask everybody not hesitate to grant instruction .

Due to the text , The relevant experimental projects in this paper cannot be shown , Resources have been uploaded , You can download it yourself .

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