You will need

- resistor, an ohmmeter, a multimeter, a magnifying glass.

Instruction

1

The easiest way to determine

**the resistance****of the resistor**is to learn about it from the relevant documentation. If the resistor is purchased as a standalone item, find the supporting documents (invoice, warranty card, etc.). Find in them the value**of the resistor**. Most likely, the resistance value will be specified next to the part name, for example, a resistor of 4.7 K. In this case, the number means the value**of the resistor**, and the letter (s) is a unit of measurement. Options K, K, Kom, kom, Kom, kom correspond to kiloohm.The same designation with the letter "M" instead of "to" - megohms. If the letter "m" will be lowercase (small), theoretically this corresponds to a milliohm. However, in practice, such resistors are not normally sold, but are made independently from several coils of special wire. Therefore, combinations with the letter "m" can be attributed to the megohms (in unusual cases, it is better to specify).The lack of after the number of units or the presence of the word "Om" or "om" means, respectively, in Ohms. (in practice, may mean that the seller simply does not have the unit).2

If the resistor is part of an electric (electronic) devices take the electrical diagram of this device. If no schematic, try to find it on the Internet. Look at the diagram of the corresponding resistor. Resistors are indicated by small rectangles with lines emerging from the short sides. Inside the rectangle can be dashes (represent power). To the designation of the

**resistor**(rectangle) is usually the letter R and a numeral indicating the ordinal number**of the resistor**in the circuit, for example, R10. After the designation**of the resistor**indicate its value (slightly to the right or below). If**the resistance****of the resistor**is not specified, the view in the lower part of the diagram – sometimes resistor values (grouped by values) are in there.3

If you have a ohmmeter or multimeter, just connect the device to the conclusions

**of the resistor**and record the readings. Pre-multimeter switch to the measurement mode of resistance. If the ohmmeter "rolls" or on the contrary, shows a very small value, set it to any range. If the resistor is part of the scheme, the pre-wipaire it, otherwise the readings will probably be incorrect (smaller).4

The value

The letter is put in place and the decimal point represents a multiple of the prefix:K – kilo Ohm;

M – Megohm;

E – units, i.e. in this case Om.If the value

**of the resistor**can also be identified by its marking. If the denomination consists of two digits and one letter (typically for the old "Soviet" parts), then use the following rule:The letter is put in place and the decimal point represents a multiple of the prefix:K – kilo Ohm;

M – Megohm;

E – units, i.e. in this case Om.If the value

**of the resistor**is an integer, then the corresponding letter is used at the end of the designation (69К = 69 kOhm). If**the resistance****of the resistor**is less than one letter is placed before the number (M15 = 0.15 Mω = 150 kω). In fractional denominations of the letter is between numbers (9Е5 = 9.5 Ohm).5

Numbers consisting of three digits, remember the following simple rule: the first two digits need to add as many zeros as indicated by the third digit. For example, 162, 690, 166 interpreted as follows:162 = 16’00 Ohms = 1.6 kω;

690 = 69’ Om = 69 Ohms;

166 = 16’000000 Ohm = 16 MOhm.

690 = 69’ Om = 69 Ohms;

166 = 16’000000 Ohm = 16 MOhm.

6

If the value

brown - 1;

red - 2;

- orange - 3;

- yellow - 4;

green - 5;

blue - 6;

purple - 7;

gray - 8;

- white - 9.After receiving a three-digit number, use the rule described in the preceding paragraph. So for example, if the color of the three stripes in the following order, i.e. from left to right (red - 2, orange - 3, yellow - 4), we obtain the number 234, which corresponds to the nominal value of 230000 Ohms = 230 kω. By the way, the above table is very easy to remember. Order medium colors corresponding to the rainbow, and extreme color to the end of the list become lighter.

**of the resistor is**marked with colored stripes, turn it off (or turn) to the individual (apart from three) strip was to the right. Then, using the following table, match colors, put the color stripes in the numbers are: black - 0;brown - 1;

red - 2;

- orange - 3;

- yellow - 4;

green - 5;

blue - 6;

purple - 7;

gray - 8;

- white - 9.After receiving a three-digit number, use the rule described in the preceding paragraph. So for example, if the color of the three stripes in the following order, i.e. from left to right (red - 2, orange - 3, yellow - 4), we obtain the number 234, which corresponds to the nominal value of 230000 Ohms = 230 kω. By the way, the above table is very easy to remember. Order medium colors corresponding to the rainbow, and extreme color to the end of the list become lighter.

# Advice 2: How to determine the power resistor

To determine the power

**resistor**, take a voltmeter and connect in parallel to the resistor in the circuit. Then turn on the ammeter in the circuit. Take readings of current and voltage and multiply their values, the result is a**power**current to the resistor. It is possible to measure**the power****of the resistor**and knowing the resistance and one of the values of the current or voltage or by using a special device – power meter.You will need

- A current source, ammeter, voltmeter, ohmmeter and wattmeter.

Instruction

1

Determination of the power

**resistor**with a voltmeter and ammeter Assemble an electrical circuit, which enable the resistor and the ammeter. To the terminals**of the resistor**connect the voltmeter. When connected to a DC power source observe the rules of connection devices (the positive pole of the device always connect to the positive pole of the current source). After connecting the circuit to the current source, remove the current reading is in amperes (ammeter) and voltage in volts (voltmeter). The resulting values multiply (P=UI), and the result is a**power****resistor**in watts.2

Determination of the power

**resistor**with a voltmeter If the resistance**of the resistor**is known (it is specified directly on the case or measure it with an ohmmeter), connect it to the terminals of the voltmeter. The assembled circuit connect to power source. Measure the voltage across the resistor in volts. Next, take the value of the voltage in the square, and divide by the resistance (P=U2/R and**power****resistor**.3

Determination of the power

**resistor**the ammeter When the known impedance circuit to the power supply, including successively ammeter. Measure the amperage in the circuit by the ammeter in amperes. Next, take the value of the current in the square and multiply by the resistance value**of the resistor**(P=I2R).4

Determination of the power

**resistor**the power meter Assemble the circuit consisting of a**resistor**and parallel connected to the power meter. Connecting it to a power source, see**power****resistor**on the scale or screen of the device. Units, in this case, adjust within the permitted device. It can be watts, milliwatts, kilowatts, etc.Note

In all cases, in order to collect safety circuit is disabled when the current source.

# Advice 3: How to measure the resistance of the resistor

The resistor is one of the main elements of any electrical circuit. Its main purpose is to create a certain resistance. Resistance can be measured with special devices or to identify a special marking on the body of the resistor.

You will need

- tester;
- calculator;
- table of markings.

Instruction

1

Take a tester who can work in ohmmeter mode. Connect it to the contacts

**of the resistor**and perform measurement. Since the resistance of the resistors is very different, adjust the sensitivity of the instrument. If the tester can only measure current and resistance, take the current source and assemble electric circuit including a resistor. When connecting the chain, be sure to monitor the current which passes through it, so as not to cause a short circuit. After the change of current in amperes, switch the tester to measure voltage. Connect it in parallel with the resistor and take readings in volts. Then find the resistance**of the resistor**by dividing the voltage value U and the current I (R=U/I). If you are using a constant current source, connecting devices2

If the resistor marked to find its resistance, without resorting to additional operations. Resistors are marked or digits or combination of numbers with letters, or a set of color bars.

3

If the resistor is indicated with three digits, the first two numbers identify tens and ones number, and the third digit is the degree 10 to which it should be raised to obtain the correct values. For example, if the resistor numbered 482, it means that its resistance is equal to 48∙102=4800 Ohms.

4

When the resistor marking SMD, the first two figures are taken as the coefficient, and the letter corresponds to the degree 10 to which it needs to multiply. All the values of the coefficients and the letters get in the table of marking of the SMD resistors EIA. The resistor may be the fourth letter of its accuracy. For example, if a resistor is marked 21ВF, its resistance will be equal to 162∙10=1620 Ohms ±1%.

5

If the drawn resistor color bands, use the table to determine the resistance

**of the resistor**by the colored marking. The first three labels correspond to the numbers that make up a coefficient, and the fourth – power of 10 by which to multiply the resulting factor.# Advice 4: How to find the value of the resistor

Designation

**of the values of**resistors on the schematics and the components are performed according to different standards. In addition, some**resistors**for the encoding numbers are used instead of numbers, the color of the ring.Instruction

1

On the wiring diagram the resistor are given without specifying the unit of measurement is generally expressed in ohms. For example, the number 200 means 200 Ohms. If after the numbers located lowercase letter K, we are talking about Kromah: 250 to 250 is file com. If the old schemes unit of measurement in the designation is absent, and the number in addition to a part is and the fractional, the value is expressed in megohms: 10,0 stands for 10 MW. On new schemes to do this, use the capital letter M: 5 M means 5 Mω. Capital letter G replaces the unit dimension D (gigaom). These resistors are rare, mainly in radiation equipment based on ionization chambers.

2

On the

**resistors**instead of using the name Om unit uses either the Latin capital letter R or a capital Greek letter Ω (omega"). Kilome are denoted by the capital letter K, megohms - capital letter M, higami - uppercase Russian letter G Latin or G. the Numbers located before and after the letters is the equivalent of digits after the decimal point. For example, 2R5 - 2.5 Ohm, 120K - 120 ohms, 4М7 - 4.7 Mω. Less the resistance value is specified using the conventional notation of units, for example, 10 kω.3

Using the color rings on

**the resistors**are coded with different numbers. The following colors are used: black - 0, brown - 1, red - 2, orange - 3, yellow - 4, green - 5, blue - 6, violet - 7, grey - 8, white - 9. These bands may be three or four. All of them, except the last, represent numbers, and the last is number of zeros following those digits. The resulting number expresses the resistance in ohms, which can be converted to more convenient units.4

If after them after a short period of located gold band, the resistor has a tolerance of 5%. The silver band tells about the tolerance of 10%, and if it does not exist, the tolerance on resistance equal to 20%. Countdown guide strips on the side opposite the strip, symbolizing tolerance.

5

The resistor on which the marking is absent, the resistance can be measured. To do this, power off the circuit, discharge the capacitors, confirm with a voltmeter that they are really discharged, and then desolder one lead of the resistor and connect it to an ohmmeter. Select the limit at which resistance is displayed most accurately. After reading the readings, disconnect the ohmmeter and solder the disconnected output back.