Sensitive voltage detector
Wednesday, September 7, 2011
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| Sensitive voltage detector schematic diagram |
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| Sensitive voltage detector illustration |
Showing posts with label DC SCHEMATIC DIAGRAM. Show all posts
Showing posts with label DC SCHEMATIC DIAGRAM. Show all posts
Make your own multimeter
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| Make your own multimeter schematic diagram |
First, you need to determine the characteristics of your meter movement. Most important is to know the full scale deflection in milliamps or microamps. To determine this, connect the meter movement, a potentiometer, battery, and digital ammeter in series. Adjust the potentiometer until the meter movement is deflected exactly to full-scale. Read the ammeter’s display to find the full-scale current value:
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| Make your own multimeter illustration |
Thermoelectricity
Tuesday, September 6, 2011
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| Thermoelectricity schematic diagram |
Twist one end of the iron wire together with one end of the copper wire. Connect the free ends of these wires to respective terminals on a terminal strip. Set your voltmeter to its most sensitive range and connect it to the terminals where the wires attach. The meter should indicate nearly zero voltage.
What you have just constructed is a thermocouple: a device which generates a small voltage proportional to the temperature difference between the tip and the meter connection points. When the tip is at a temperature equal to the terminal strip, there will be no voltage produced, and thus no indication seen on the voltmeter.
What you have just constructed is a thermocouple: a device which generates a small voltage proportional to the temperature difference between the tip and the meter connection points. When the tip is at a temperature equal to the terminal strip, there will be no voltage produced, and thus no indication seen on the voltmeter.
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| Thermoelectricity illustration |
A very simple computer
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| A very simple computer schematic diagram |
This deceptively crude circuit performs the function ofmathematically averaging three voltage signals together, and so fulfills a specialized computational role. In other words, it is a computer that can only do one mathematical operation: averaging three quantities together.
Build this circuit as shown and measure all battery voltages with a voltmeter. Write these voltage figures on paper and average them together (E1 + E2 + E3, divided by three). When you measure each battery voltage, keep the black test probe connected to the ”ground” point (the side of the battery directly joined to the other batteries by jumper wires), and touch the red probe to the other battery terminal. Polarity is important here! You will notice one battery in the schematic diagram connected ”backward” to the other two, negative side ”up.” This
battery’s voltage should read as a negative quantity when measured by a properly connected digital meter, the other batteries measuring positive.
Build this circuit as shown and measure all battery voltages with a voltmeter. Write these voltage figures on paper and average them together (E1 + E2 + E3, divided by three). When you measure each battery voltage, keep the black test probe connected to the ”ground” point (the side of the battery directly joined to the other batteries by jumper wires), and touch the red probe to the other battery terminal. Polarity is important here! You will notice one battery in the schematic diagram connected ”backward” to the other two, negative side ”up.” This
battery’s voltage should read as a negative quantity when measured by a properly connected digital meter, the other batteries measuring positive.
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| A very simple computer illustration |
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| A very simple computer illustration |
Potentiometer as a rheostat
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| Potentiometer as a rheostat schema diagram |
Potentiometers find their most sophisticated application as voltage dividers, where shaft position determines a specific voltage division ratio. However, there are applications where we don’t necessarily need a variable voltage divider, but merely a variable resistor: a two-terminal device. Technically, a variable resistor is known as a rheostat, but potentiometers can be made to function as rheostats quite easily.
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| Potentiometer as a rheostat illustration |
Potentiometer as a voltage divider
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| Potentiometer as a voltage divider schematic diagram |
Begin this experiment with the pencil ”lead” circuit. Pencils use a rod made of a graphiteclay mixture, not lead (the metal), to make black marks on paper. Graphite, being a mediocre electrical conductor, acts as a resistor connected across the battery by the two alligator-clip jumper wires. Connect the voltmeter as shown and touch the red test probe to the graphite rod. Move the red probe along the length of the rod and notice the voltmeter’s indication change. What probe position gives the greatest voltage indication?
Essentially, the rod acts as a pair of resistors, the ratio between the two resistances established by the position of the red test probe along the rod’s length:
Essentially, the rod acts as a pair of resistors, the ratio between the two resistances established by the position of the red test probe along the rod’s length:
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| Potentiometer as a voltage divider illustration |
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| Potentiometer as a voltage divider illustration 01 |
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| Potentiometer as a voltage divider illustration 02 |
Current divider
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| Current divider schematic diagram |
Once again, I show differentmethods of constructing the same circuit: breadboard, terminal strip, and ”free-form.” Experiment with all these construction formats and become familiar with their respective advantages and disadvantages.
Select three resistors from your resistor assortment and measure the resistance of each one with an ohmmeter. Note these resistance values with pen and paper, for reference in your circuit calculations.
Connect the three resistors in parallel to and each other, and with the 6-volt battery, as shown in the illustrations. Measure battery voltage with a voltmeter after the resistors have been connected to it, noting this voltage figure on paper as well. It is advisable to measure battery voltage while its powering the resistor circuit because this voltage may differ slightly from a no-load condition.
Select three resistors from your resistor assortment and measure the resistance of each one with an ohmmeter. Note these resistance values with pen and paper, for reference in your circuit calculations.
Connect the three resistors in parallel to and each other, and with the 6-volt battery, as shown in the illustrations. Measure battery voltage with a voltmeter after the resistors have been connected to it, noting this voltage figure on paper as well. It is advisable to measure battery voltage while its powering the resistor circuit because this voltage may differ slightly from a no-load condition.
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| Current divider illustration |
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| Current divider illustration 01 |
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| Current divider illustration 02 |
Voltage divider
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| Voltage divider schematic diagram |
Shown here are three different methods of circuit construction: on a breadboard, on a terminal strip, and ”free-form.” Try building the same circuit each way to familiarize yourself with the different construction techniques and their respective merits. The ”free-form” method – where all components are connected together with ”alligator-” style jumper wires – is the least professional, but appropriate for a simple experiment such as this. Breadboard construction is versatile and allows for high component density (many parts in a small space), but is quite temporary. Terminal strips offer a much more permanent form of construction at the cost of
low component density.
Select three resistors from your resistor assortment and measure the resistance of each one with an ohmmeter. Note these resistance values with pen and paper, for reference in your circuit calculations.
Connect the three resistors in series, and to the 6-volt battery, as shown in the illustrations.
Measure battery voltage with a voltmeter after the resistors have been connected to it, noting this voltage figure on paper as well. It is advisable to measure battery voltage while its powering the resistor circuit because this voltage may differ slightly from a no-load condition. We saw this effect exaggerated in the ”parallel battery” experiment while powering a high-wattage lamp: battery voltage tends to ”sag” or ”droop” under load. Although this three-resistor circuit should not present a heavy enough load (not enough current drawn) to cause significant voltage ”sag,” measuring battery voltage under load is a good scientific practice because it provides more realistic data.
low component density.
Select three resistors from your resistor assortment and measure the resistance of each one with an ohmmeter. Note these resistance values with pen and paper, for reference in your circuit calculations.
Connect the three resistors in series, and to the 6-volt battery, as shown in the illustrations.
Measure battery voltage with a voltmeter after the resistors have been connected to it, noting this voltage figure on paper as well. It is advisable to measure battery voltage while its powering the resistor circuit because this voltage may differ slightly from a no-load condition. We saw this effect exaggerated in the ”parallel battery” experiment while powering a high-wattage lamp: battery voltage tends to ”sag” or ”droop” under load. Although this three-resistor circuit should not present a heavy enough load (not enough current drawn) to cause significant voltage ”sag,” measuring battery voltage under load is a good scientific practice because it provides more realistic data.
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| Voltage divider illustration |
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| Voltage divider illustration 01 |
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| Voltage divider illustration 02 |
Parallel batteries
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| Parallel batteries schematic diagram |
Begin this experiment by connecting one 6-volt battery to the lamp. The lamp, designed to operate on 12 volts, should glow dimly when powered by the 6-volt battery. Use your voltmeter to read voltage across the lamp like this:
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| Parallel batteries Illustration |
Series batteries
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| Series batteries schematic diagram |
Connecting components in series means to connect them in-line with each other, so that there is but a single path for electrons to flow through them all. If you connect batteries so that the positive of one connects to the negative of the other, you will find that their respective voltages add. Measure the voltage across each battery individually as they are connected, then measure the total voltage across them both, like this:
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| Series batteries illustration |
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