Multimeter

Multimeter 

A Multimeter  is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance,Continuity and etc .

There are two types of Multimeters

1. Analog Multimeters
2. Digital Multimeters

Analog multimeters use a Microammeter with a moving pointer to display readings and Digital multimeters  have a numeric display.

 Now a days most of peoples Uses digital multimeter so we disscuss aout it .

 Digital Multimeter function Instructions

Figure 1. Auto range select DMM     

                                                                     Figure 2. Simple DMM

1. DC V Function :- Measures DC volts. Auto-ranging from 0 to 600 volts 

2.AC V Function :- Measures AC volts. Auto-ranging from 0 to 600 volts 

3. Resistance Function :-  Measures resistance. Autoranging from 0 to 20MW.

4. AC mA Function :-Measures AC current in milliamps. One range: 0 to 200 milliamps.

5. DIODE Function :- For testing diodes.

6. CONTINUITY Function :- Tests for continuity between two points.

7. Volts, mA, OHMS, BAT, DIODE and CONTINUITY Input Jack.

8. COM Input Jack :- Common Input Jack.

9. DC10A Input Jack. For red test lead probe connection when measuring high DC current (max10A)

10. DC10A Function :- Measures DC current. One range: 10Amps (DC from 0 to 10 amperes).

11. DCmA Function :- Measures DC current in Milliamps. One range: 0 to 200 milliamps.

12. Battery Test Function :- 4 ranges and three LEDS (green, yellow and red). Tests small batteries.

13. OFF Function :- Turns unit "off" when function is selected.

14. Function/Range Selector Switch :- Selects desired function or range.

15. Liquid Crystal Display (LCD) :- Displays results of tests or measurements.

          Figure 1 shown the auto range select multimeter and Figure 2 shown the Simple digital multimeter in simple digital multi meter.we can select/change  the range whtever we need/want  now we Discuss how it works Properly .....

How to use Multimeter ?

(A) How do I measure voltage ?

1. Plug your Black and Red probes into the appropriate sockets on your multimeter. Regurarly The black probe should be plugged into the socket labeled "COM," and the red probe into the socket labeled with a "V"(AC or DC )
2. Choose the appropriate voltage setting on your multimeter's dial.
3. Touch the probe tips to your circuit in parallel with the element you want to measure voltage across  Then whatever your voltage is display or shown on the screen of your multimeter. 

4. If your multimeter is not auto-ranging, you might need to adjust the range. If your multimeter's screen just reads "0," then the range you have selected is probably too high. If the screen reads "OVER," "OL," or "1" these are different ways of saying "overload", then the range you have selected is too low. If this happens, adjust your range up or down as necessary.

(B) How do I measure current ?

1. Plug your red and black probes into the appropriate sockets on the multimeter. Regularly ,  The black probe should be plugged into the socket labeled "COM." There might be multiple sockets for measuring current, with labels like "10A" Or "mA"(AC or DC).
2. Choose the appropriate current setting on your multimeter. Remember to check if your circuit is direct current or alternating current, and that almost all battery-powered circuits will be direct current. If your meter is not auto-ranging, you might need to guess at the scale to use and you can change this later if you don't get a good reading .
3. Connect the multimeter probes in series to the current you want to measure Be sure to use the red probe toward the battery's positive side, otherwise your current reading will be Negative. Then whatever your voltage is display or shown on the screen of your multimeter. 
4. If your multimeter is not auto-ranging, you might need to adjust the range. If your multimeter's screen just reads "0," then the range you have selected is probably too high. If the screen reads "OVER," "OL," or "1" these are different ways of saying "overload", then the range you have selected is too low. If this happens, adjust your range up or down as necessary 

(C) How do I measure resistance?

1. Plug your Red and black probes into the appropriate sockets on your multimeter. Regularly the black probe should be plugged into the socket labeled "COM," and the red probe should be plugged into the socket labeled with an "Ω" symbol.
2. Choose the appropriate resistance measurement setting on your multimeter's dial. If you have an estimate for the resistance you will be measuring Important: Turn off the power supply to your circuit before measuring resistance. If your circuit has a power switch, you can do this by turning the switch "off." If there is no switch, you can remove the batteries. If you do not do this, your reading might be incorrect. If your circuit has multiple components, you might need to remove the component you want to measure in order to accurately determine its resistance. For example, if your circuit has two resistors in parallel, you will have to remove one resistor to measure their resistances individually.
3.  Connect one of your multimeter's probes to each side of the object whose resistance you want to measure. Resistance is always positive and the same in both directions, so it does not matter if you switch the black and red probes in this case
4. If your multimeter is not auto-ranging, you might need to adjust the range. If your multimeter's screen just reads "0," then the range you have selected is probably too high. If the screen reads "OVER," "OL," or "1" these are different ways of saying "overload", then the range you have selected is too low. If this happens, adjust your range up or down as necessary.

(D) How do I do a continuity check?

1. Set your multimeter to the continuity check symbol. Remember that this symbol might not look the same on all multimeters.
2. Plug your probes into the appropriate sockets. Regularly , The black probe should go into the socket labeled "COM," and the red probe should go into Continuty check.
3. Important: Turn off the power supply to your circuit before doing a continuity check. If your circuit has a power switch, you can do this by turning the switch "off." If there is no switch, you can remove the batteries.
4. Touch two parts of your circuit with the probes. If the two parts of the circuit are electrically connected with very little resistance between them, your multimeter should beep. If they are not connected, it will not make a noise and might display something on the screen such as "OL," "OVER," or "1," which all stand for "overload." The easiest way to test this function with your multimeter is to check it with a single piece of conductive material  and a piece of non-conducting material, like wood or plastic.