Electrical4U 
Oscilloscopes, like a multimeter, have finite measurement limits. An oscilloscope result depends on analogue bandwidth, rise time, sample rate, record length, noise, input range and the connected probe system.Analogue bandwidth is normally specified as the frequency at which a sine wave is displayed at 70.7% of its low-frequency amplitude, a reduction of 3 dB. Sample … Read more
Schering Bridge Theory A Schering Bridge is an AC four-arm network that measures a capacitor’s capacitance and its dissipation factor. The same reading, with known electrode geometry, gives relative permittivity of a dielectric. The Schering Bridge circuit is below.c1 is the unknown capacitance. r1 is its series equivalent loss resistance. c2 is a low-loss standard … Read more
What is an Electric Motor? An electric motor (or electrical motor) is a machine that converts electrical energy into mechanical energy. Current in a winding sits in the motor magnetic field and produces torque on the shaft. That force is the Lorentz force on a current in a magnetic field. Faraday’s Law covers induced emf, … Read more
What is an Ohmmeter? An ohmmeter, also written as ohm meter, measures electrical resistance. The instrument applies a known test stimulus and measures the response produced by electric current. Micro-ohmmeters and milliohmmeters are designed for very low values, while Megohmmeters, including instruments made by Megger, use higher test voltages to measure insulation resistance. A measured … Read more
Hay, Maxwell and Anderson already cover much inductor work. Hay’s bridge suits quality factor above 10. Maxwell’s bridge suits Q from about 1 to 10. Anderson bridge covers a wide L span. Owens Bridge is the Owen L-C bridge used when you want that wide L span in terms of a standard capacitor, including incremental … Read more
Armature reaction is the armature mmf acting on the main field. At no load the magnetic neutral axis sits on the geometrical neutral axis, so the brushes sit there too. On load the armature flux lies along the interpolar axis and looks roughly triangular. That brush-axis mmf cross-magnetizes the main field. Flux crowds at the … Read more
A servo motor is a closed-loop actuator built around a servomechanism. The loop holds shaft angle, and often speed or torque, to a command. An open-loop DC motor is a poor fit for a control-surface position loop such as an aircraft tail. The pages below cover common places that closed-loop motor shows up. Servo Motor in … Read more
What is Maxwell Bridge A Maxwell Inductance Capacitance Bridge is a four-arm AC Wheatstone bridge used to measure self-inductance by a null. The unknown coil sits in one arm. A parallel resistor and capacitor in the opposite arm make the Maxwell-Wien form. The inductive arm has a lagging phase. The capacitive arm has a leading … Read more
What Are Flexible AC Transmission Systems (FACTS)? FACTS stands for Flexible AC Transmission Systems. IEEE defines the term as AC transmission systems that use power-electronic and other static controllers to improve controllability and power-transfer capability. Depending on the controller, FACTS can regulate voltage, supply or absorb reactive power, change effective line impedance or control power … Read more
What Is a Strain Gauge? A bonded resistance strain gauge measures deformation at the surface of a component. Strain is the change in length divided by the original length, so it is dimensionless and is often reported in microstrain. When the component stretches or compresses along the gauge axis, the bonded measuring grid deforms with … Read more