Bridge circuit
A circuit composed of a source and four impedances that is used in the measurement of a wide range of physical quantities. The bridge circuit is useful in measuring impedances (resistors, capacitors, and inductors) and in converting signals from transducers to related voltage or current signals. See Capacitor, Inductor, Resistor
The bridge impedances Z1, Z2, Z3, Z4, shown in the illustration may be single impedances (resistor, capacitor, or inductor), combinations of impedances, or a transducer with varying impedance. For example, strain gages are resistive transducers whose resistance changes when they are deformed.
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Bridge circuits are often used with transducers to convert physical quantities (temperature, displacement, pressure) to electrical quantities (voltage and current). High-accuracy voltmeters and ammeters are relatively inexpensive, and the voltage form of a signal is usually most convenient for information display, control decisions, and data storage. Another important advantage of the bridge circuit is that it provides greater measurement sensitivity than the transducer.
The bridge circuit is balanced when the output read by the meter is zero. In this condition the voltages on both sides of the meter are identical. The bridge is used in two forms. The null adjustment method requires adjustment of a calibrated impedance to balance it. In this case the meter is usually a highly sensitive current-measuring galvanometer. The null adjustment method is often used to measure impedances, with the output read from a dial attached to the adjustable impedance. The deflection method requires on accurate meter in the bridge to measure the deviation from the balance condition. The deviation is proportional to the quantity being measured.
There are many special forms of the bridge circuit. When all of the impedances are resistive, it is commonly called a Wheatstone bridge. Other common forms use a current source in place of the voltage source, a sinusoidal source in place of a constant (dc) source, or branch impedances which are specific combinations of single passive impedances. The bridge circuit is also used in a variety of electrical applications varying from oscillators to instrumentation amplifier circuits for extremely accurate measurements. See Wheatstone bridge
Bridge circuit
A circuit composed of a source and four impedances that is used in the measurement of a wide range of physical quantities. The bridge circuit is useful in measuring impedances (resistors, capacitors, and inductors) and in converting signals from transducers to related voltage or current signals. See Capacitor, Inductor, Transducer
The bridge impedances Z1, Z2, Z3, Z4, shown in the illustration may be single impedances (resistor, capacitor, or inductor), combinations of impedances, or a transducer with varying impedance. For example, strain gages are resistive transducers whose resistance changes when they are deformed.
)
Bridge circuits are often used with transducers to convert physical quantities (temperature, displacement, pressure) to electrical quantities (voltage and current). High‐accuracy voltmeters and ammeters are relatively inexpensive, and the voltage form of a signal is usually most convenient for information display, control decisions, and data storage. Another important advantage of the bridge circuit is that it provides greater measurement sensitivity than the transducer.
The bridge circuit is balanced when the output read by the meter is zero. In this condition the voltages on both sides of the meter are identical. The bridge is used in two forms. The null adjustment method requires adjustment of a calibrated impedance to balance it. In this case the meter is usually a highly sensitive current-measuring galvanometer. The null adjustment method is often used to measure impedances, with the output read from a dial attached to the adjustable impedance. The deflection method requires on accurate meter in the bridge to measure the deviation from the balance condition. The deviation is proportional to the quantity being measured.
There are many special forms of the bridge circuit. When all of the impedances are resistive, it is commonly called a Wheatstone bridge. Other common forms use a current source in place of the voltage source, a sinusoidal source in place of a constant (dc) source, or branch impedances which are specific combinations of single passive impedances. The bridge circuit is also used in a variety of electrical applications varying from oscillators to instrumentation amplifier circuits for extremely accurate measurements. See Instrumentation amplifier, Oscillator
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