AC Bridge Circuits :: Papers

AC Bridge Circuits As we saw with DC bar turns, the circuit configuration cognise as a bridge stand be a genuinely useful way to footprint unusual values of resistance. This is true with AC as well, and we can apply the very same principle to the accurate measurement of unknown impedances. To review, the bridge circuit works as a pair of two-component voltage dividers connected crossways the same source voltage, with a profitless-detector meter movement connected in the midst of them to indicate a designate of balance at zero volts IMAGE both one of the four resistors in the above bridge can be the resistor of unknown value, and its value can be determined by a ratio of the other three, which are calibrated, or whose resistances are known to a precise degree. When the bridge is in a balanced condition (zero voltage as indicated by the null detector), the ratio works issue to be this IMAGE One of the advantages of using a bridge circuit to measure resistance is that the voltage of the power source is irrelevant. Practically speaking, the higher the yield voltage, the easier it is to detect a condition of imbalance between the four resistors with the null detector, and thus the more sensitive it will be. A greater leave voltage leads to the possibility of increased measurement precision. However, there will be no fundamental error introduced as a result of a lesser or greater power supply voltage irrelevant other types of resistance measurement schemes. Impedance bridges work the same, unless the balance equation is with complex quantities, as both magnitude and class across the components of the two dividers must be equal in pitch for the null detector to indicate zero. The null detector, of course, must be a device capable of detecting very small AC voltages. An scope is often used for this, although very sensitive electromechanical meter movements and tear down headphones (sm all speakers) may be used if the source frequency is within audio frequency range. One way to maximize the effectiveness of audio headphones as a null