Category: Electrical & Electronics Measurements
-
The Principle of Operation of an Induction Potentiometer
An induction potentiometer is a rotary type linear-variable inductor with two concentrated windings wound on the stator and on the rotor as illustrated in the figure below: The rotor windings are excited with an AC, inducing voltage in the stator windings. The amplitude of the output is dependent on mutual inductance between the two coils,…
-
The Principle of Operation of a Digital Frequency Meter
A frequency meter/counter is a digital instrument that can measure and display the frequency of any periodic waveform. Its operation is based on the principle of gating the unknown input signal into the counter for a predetermined time. For instance, if the unknown input signal were gated into the counter for exactly 1 second, the…
-
Basic Elements of an Electronic Instrument
An electronic instrument is made up of the following key elements: Transducer This is the first sensing element and is needed only when measuring a non-electrical quantity such as pressure or temperature. Its task is to convert the non-electrical physical quantity into an electrical signal. An example of a transducer is a thermocouple for sensing…
-
Electrical vs. Electronic Instruments
Despite the fact that both electrical and electronic instruments measure electrical quantities like voltage and current, they differ from each other in terms of the built-in features; for example, purely electrical instruments don’t possess any in-built amplifying device to increase the amplitude of the quantity being measured whereas electronic instruments typically incorporate an amplifier. DC…
-
Optical Time Domain Reflectometer (OTDR)
The commonly employed technique for analysing the state of a fibre optic is to test it with an Optical Time Domain Reflectometer (OTDR). The OTDR uses backscattered light of the fibre to imply loss. The OTDR works is similar way to RADAR, sending a high power laser light pulse down the fibre and looking for…
-
Basic Features of a DC Potentiometer
A potentiometer is an instrument that is used for measurement of potential difference across a known resistance or between two terminals of a circuit or network of known characteristics. A potentiometer is also used for comparing the emf of two cells. A potentiometer is widely used in measurements where the precision required is higher than…
-
Features and Applications of Instrument Transformers
Instrument transformers are used in the measurement of voltage, current, energy, and power in ac circuits. The main reasons why instrument transformers are employed in measurements are: In power systems, the levels of currents and voltages handled are very high, and therefore direct measurements with conventional instruments is not possible without compromising the operator safety,…
-
Power Measurement in AC Circuits (Single-phase & Polyphase Systems)
Introduction to AC Power Measurement In alternating current circuits, the instantaneous power varies continuously as the voltage and current varies while going through a cycle. In this case the power at any instant is given by: p(t) = v(t) x i(t) Where, p(t), v(t) and i(t) are the values of instantaneous power, voltage and current…
-
Performance Characteristics of Digital Measurement Instruments
In this article, we discuss the performance characteristics of digital instruments i.e. Resolution Accuracy Linear errors Settling time Temperature sensitivity Monotonicity Resolution This is defined as the smallest increment in voltage that can be discerned. It is the reciprocal of the number of discrete steps in the Digital to Analog (D/A) converter input. Resolution depends…
-
Key Instruments Used By Electronics Engineers
Multimeter This is also called volt-ohm-milliammeter (VOM). It is a general purpose instrument having the circuitry and switching arrangement for measuring ac/dc voltage or ac/dc current or resistance. It is simple, compact and portable instrument because the only power it uses is the battery for the ohm-meter. Multimeters can be analog or digital type. Multimeters…