Done by: Khalid Hijjawi Mohammad Massad

 Is an electrical instrument that measures electrical resistance, the opposition to an electric current. The unit of measurement for resistance is ohms ( Ω ). Ω

 The main principle that ohmmeter works with is: R=V/I (Ohm’s Law)

Types of ohmmeters 1.Analog ohmmeters 2.Digital ohmmeters

Analog Ohmmeters 1.Series type ohmmeter: R1:the currernt limiting resistor R2: Zero adjust resistor Rx: Unknown resistor E: internal battery Rm: internal resistance of the d’Arsonval movement

2.Shunt type ohmmeter: same as series type but used for low resistance measurements because of its high accuracy

 1. Measuring the resistance when the circuit element is connected as part of a larger circuit

 2. You cannot measure the "resistance" of a non-linear element although ohmme ters can be used to identify the P and N sides of a diode

 3. Measuring while your hands touching the leads of the circuit element

Mega ohmmeter  is a special type of ohmmeter used to measure the electrical resistance of insulators. Insulating components, for example cable jackets, must be tested for their insulation due to their usage in high voltage electrical equipment and installations.

 For this purpose megohmmeters, which can provide high DC voltages (typically in ranges from 500 V to 2 kV) at specified current capacity, are used. Acceptable insulator resistance values are typically 1 to 10 megohms, depending on the standards referenced.

1.Electronic Type (Battery operated) 2.Manual Type (Hand operated)

 is a piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors.

* The signal at the output of N2 is invariably a square wave. The square waves are basically just continuous and alternate generation of the positive voltage and zero voltage. * The capacitor C X which is to be measured is connected to the output of the buffers as shown in the figure. * During a positive peak of the square wave, the unknown capacitor C X charges up to the supply voltage and at the next zero voltage pulse it discharges almost instantly through D1.

LCR meter An LCR meter (Inductance (l), Capacitance (C), and Resistance (R)) is an instrument used to measure the inductance, capacitance, and resistance of a component, sensor or other device that’s operation depends upon capacitance, inductance or resistance.

 Test frequency : An instrument with a wide frequency range and multiple programmable frequencies provides this platform. Common measurement frequencies are 50/60Hz, 120Hz, 1kHz, 100kHz and 1MHz

At the balance point the bridge component positions can be used to determine the value of the component under test. This method is typically used for lower frequency measurements - often measurement frequencies of up to 100 kHz or so are used.

Diode measurement - One of the basic ohmmeter application, is the determination of cathode and anaode. - Also determining the forward active mode resistance.

 The resistance of forward active mode is very low compared to the resistance of reversed mode. So based on this the cathode and anode is determined.

 There may be some errors in measuring the forward resistance.