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Electronic bridges are bridges that are used to cross from one circuit, channel, board, or element to another circuit, channel, board or element. Bridges are the most accurate types of measuring devices used to measure all kinds of electrical values.
Types of bridges
There are many types of electronic bridges available, such as Wheatstone Circuit Bridge, H Circuit Bridge, etc.
Wheatstone Circuit Bridge:
Wheatstone circuit bridge is the standard electrical bridge circuit, which are used to measure resistance.
Structure
Wheatstone circuit bridges comprises of a common electric current source like a battery and a galvanometer. The battery and galvanometer connects two parallel branches. Each branch consists of two resistors, of which, one branch contains a known resistance and an unknown resistance, while the other parallel branch contains resistors of known values.
Working
In Wheatstone Circuit Bridge, the resistor is measured by adjusting values of resistance on parallel branches. To be precise, the value of unknown resistor is determined by adjusting the values of other three resistances until the current passing through the galvanometer decreases, and becomes zero. In other words, unknown resistance is determined by balancing the circuit.
H Circuit Bridge
An H-bridge is an electronic circuit bridge that is used to run DC electric motors forwards or backwards.
Construction & Structure
A solid-state H-bridge is constructed by using reverse polarity devices, such as PNP or NPN transistor, BJTs or MOSFET. Usually, P-channel of the MOSFET is connected to the high voltage bus while N-channel of the MOSFET is connected to the low voltage bus. However, for gaining more efficiency, N-channel of the MOSFET is used on both --high side as well as on low side-- controlled by the gate (P-channel MOSFET). An H bridge consists of four switches. Two switches on the half side of the bridge (i.e. on u part of the network) have same positive voltage while two switches on other half side of the bridge carry negative voltage.
Working
H bridge can be turned on by switching on two switches that are diagonally opposed (i.e. one on high side left and other on low side right). When diagonally opposed switches are turned on, the current flows through diagonally opposed switches in a "positive" direction. Similarly, when switches located on high side right and other on low side left is turned on, current flows in opposite direction. This condition is called `shoot through` condition.
Specifications of Electronic Bridges
AC Input Voltage Rating (V )
AC Input Voltage Rating (V) is the input voltage range at which the electronic bridges are designed to operate (such as 115, 208, 230, or 480 VAC). Generally, AC Input Voltage rating (V) is expressed in volts.
AC Input Current Rating (A)
AC Input Current Rating (A) is the range of input voltage at which the electronic bridges are designed to operate. AC Input Current Rating (A) is expressed in ampere.
DC Output Voltage Rating (V)
DC Output Voltage Rating (V) is the range of DC output voltage at which the electronic bridges are designed to operate. DC Output Voltage Rating (V) is expressed in volts.
DC Output Current Rating (A)
DC Output Current Rating (A) is the range of DC output current at which the electronic bridges are designed to operate. This is usually expressed in ampere.
Advantages of Electronic Bridges
1. Electronic bridges are capable of generating a DC output voltage, which is almost double to that of a conventional full-wave circuit rectifier.
2. Electronic bridges are used in filters, as they are capable of generating DC outputs that have high ripple frequencies.
3. Electronic bridges are used in diodes having low breakdown voltages as they are capable of reducing peak-inverse voltage (PIV)--the largest negative voltage across a single junction diode.
Applications of Electronic Bridges
· Electronic bridges find applications in an AC to DC converter, battery chargers, DC power systems, and other power system devices such as DC power supplies.
· Bridge circuits are also used in electroplating, electro coating, processing, signaling, and switching applications.
Industry served
Electronic bridges are used in telecommunications industry, automobiles industry and. military and aerospace industries.
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