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Preliminaries 1.
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RESISTORS’ COLORED CODES.
Codes may have a view of colored strips or dots. Each color has got its own definite meaning (see table). Strips put to one of the resistor’s terminal and are situated from left to right. If the size of the resistor doesn’t allow us to place strips in such a way the first strip of each resistor is made wider than others. Resistors of low accuracy (0.1%-10%) are marked with 5 colored strips. The first three are resistance in Ohms, the forth – multiplier, the fifth – accuracy. If resistors are marked with 4 colored strips the first two are resistance in Ohms, the third – multiplier, the forth -accuracy. If a resistor has got 3 colored strips it means that the first two strips are shown value of resistance in Ohms, the third one is multiplier.
| Strip’s color | Nominal resistance, Ohm | Multiplier | Tolerance, % | ||
| First strip | Second strip | Third strip | Forth strip | Fifth strip | |
| Silver | - | - | - | 0.01 | ±10 |
| Golden | - | - | - | 0.1 | ±5 |
| Black | - | - | - | ||
| Brown | ±1 | ||||
| Red | 102 | ±2 | |||
| Orange | 103 | - | |||
| Yellow | 104 | - | |||
| Green | 105 | ±0.5 | |||
| Blue | 106 | ±0.25 | |||
| Violet | 107 | ±0.1 | |||
| Gray | 108 | - | |||
| White | 109 | - |
Preliminaries 2.
MEASUREMENTS with DIGITAL MULTIMETER.
Digital multimeter is a multifunctional instrument. It can measure resistance, capacitance, DC and AC voltage, DC and AC current, short-circuit. It can help us to define transistor’s base, emitter and collector, anode and cathode for diode.
Process of measurement.
Before the work it needs to check if the instrument ready to work. For this purpose in the mode “measurement of resistance” it needs to connect test leads (range of measurement is 200 Ω). The sound signal will appear to inform us about short-circuit. It means that the instrument is suitable for measurement. This mode is used for searching short-circuit somewhere in the electric circuit. In other positions of the pointer (not “measurement of resistance”) we can see 0 on the display without contact between the leads.
Measurement of resistance.
Set the FUNCTION switch to the position “measurement of resistance” and connect the test leads across the resistor under measurement. Connect the BLACK test lead to the COM jack and the RED test lead to the V/Ω jack. After checking define range of measurement. For example, 200 Ω. If resistance of resistor under measurement is higher, the readings will be 1. Change the range. If resistance under measurement is over this range, we have got its value on the display.
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