Basic Electrical Engineering

Annexure

Department of Biomedical Engineering

Riphah International University, Islamabad

Annexure A:

Common Electrical Symbols

Basic Electrical Engineering

Annexure

Department of Biomedical Engineering

Riphah International University, Islamabad

Annexure B:

Safety Precautions: In working with electrical equipment, extreme care must be taken to avoid electrical shock to any person, and to avoid any damage to any instrument or other equipment. In this exercise, you are to investigate the circuit connections for measuring DC voltages and currents. Some important rules to remember are:

1. Carefully follow all written and verbal instructions. If you do not clearly understand a procedure or directions, ask your instructor before proceeding with the experiment.

1. Always turn off power to the circuit when changing the circuit. 2. Have your instructor check and approve your circuit before turning power on

2. Only reapply power after verifying that the circuit is properly wired and that the voltage to be applied is at or below the required value.

3. Failure to turn off power when making circuit changes is a major reason for blowing fuses in the equipment, thereby rendering the equipment unusable and wasting your time and that of others. Please carefully check circuit wiring, resistor settings, and voltage settings before applying power to the circuits.

4. To avoid possible costly instrument damage, the range of the scale for a voltmeter or an ammeter should always be larger than the magnitude of the voltage or current being measured.

5. When in doubt, start out with the highest scale or with an instrument known to have a higher range than the quantity you are measuring. It is important to note that one should use the smallest possible scale, without exceeding the range setting, for the most precise measurement.

6. Polarity must be observed on DC measurements. A voltmeter must be connected such that its positive terminal is connected to the more positive point in the circuit, and an ammeter must be connected such that current enters its positive terminal.

7. Always connect a voltmeter in parallel with the load or source being measured, and connect an ammeter in series with the load. Never connect an ammeter across a voltage source.

8. An ideal voltmeter would have infinite resistance and would not drain any current from the original circuit. However, real voltmeters have a finite resistance, which must be considered in a high-resistance circuit.

9. An ideal ammeter would have zero resistance, in which case there would be no voltage drop across the meter. However, real ammeters have some resistance, which becomes important in low-resistance circuits.

10. Rings, watches, etc.should be removed. Wearing articles of jewelry can be dangerous, since

they may serve as electrodes for the introduction of current into the body.

11. Do not work in the laboratory alone; have at least one partner or must be supervised by a

teaching assistant, faculty member, or staff member at all times.