Study of Multimeters and Testing of Components.

STUDY OF MULTIMETERS and TESTING OF COMPONENTS

AIM:

To study the use of multi meter to check voltage, current and also to check various electronic components.

MATERIALS AND TOOLS REQUIRED:

Solder, flux, knife/blade, soldering iron, desoldering pump and nose pliers.

THEORY:

A multi-meter or a multi tester, also known as a VOM (Volt-Ohm meter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multi meter would include basic features such as the ability to measure voltage, current, and resistance.  Analog multi meters use a micro ammeter whose pointer moves over a scale calibrated for all the different measurements that can be made. Digital multi-meters  display the measured value in numerals, and may also display a bar of a length proportional to the quantity being measured.

Circuit Diagram:

PROCEDURE:

DIGITAL MULTIMETER

Voltage Measurement

1. Connect the red test lead to “V-Ω” input terminal and black test lead to “COM” input terminal.
2. Set function/range switch to desired voltage type (DC/AC) and range. If magnitude of voltage is not known, set switch to highest range and reduce until a satisfactory reading is obtained.
3. Turn-Off power to the device or circuit being tested and discharge all capacitors.
4. Connect test lead to the device or circuit being measured.
5. Turn On power to the device or circuit being measured. Voltage value will appear on the digital display along with the voltage polarity.
6. Turn Off power to the device or circuit being tested and discharge all capacitors prior to disconnecting test leads.

Current Measurement

1. Connect red test lead to the “mA” input terminal for current measurements upto 200mA. Connect black test lead to “COM” input terminal.
2. Set function/range switch to desired current type (DC/AC) and range. If magnitude of curent is not known, set switch to highest range and reduce until a satisfactory reading is obtained.
3. Turn-Off power to the device or circuit being tested and discharge all capacitors
4. Open the circuit in which current is to be measured.  Now securely connect test leads in series with the load in which current is to be measured.
5. Turn-Off power to the device or circuit being tested
6. Read current value on digital display.
7. Turn Off power to the device or circuit being tested and discharge all capacitors
8. Disconnect test leads from circuit and reconnect circuit that was being tested.
9. For current measurement of 200mA or greater, connect the red test lead to “20A” input terminal & black test lead to the “COM” input terminal.  If the resistance being measured is part of a circuit, turn off power to the circuit and discharge all capacitors.

Resistance Measurement

1. Connect the red test lead to “V-Ω” input terminal and black test lead to “COM” input terminal
2. Set function/range switch to desired “Ω” position. If magnitude of resistance is not known, set switch to highest range and reduce until a satisfactory reading is obtained.
3. If the resistance being measured is part of a circuit, turn off power to the circuit and discharge all capacitors.
4. Connect test leads to the device or circuit being measured.  When measuring high resistance, be sure to connect adjacent points even if insulated, because some insulators have a relatively low insulation resistance, causing the measured resistance to be lower than actual resistance.
5. Read resistance value on digital display.  If a high resistance value is shunted by a large value of capacitance, allow digits to stabilize.

Diode Measurements

1. Connect the red test lead to “V-Ω” input terminal and black test lead to “COM” input terminal.
2. Set function/range switch to diode test position.
3. If the semiconductor junction being measured is a part of the circuit, turn off power to the circuit and discharge all capacitors.
4. Connect test leads to the device.
5. Read forward voltage value on digital display.

RESULT:

The meters were studied and the components were tested.