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PERTEMUAN 9. JEMBATAN DC&AC dan APLIKASINYA. PENDAHULUAN. Sirkuit jembatan biasanya digunakan untuk mengukur nilai komponen, seperti resistansi, induktansi, kapasitansi dan parameter sirkuit lainnya Keakurasiannya sangat tinggi. Wheatstone bridge [ CONTENTS ]. Photograph of the instrument
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PERTEMUAN 9 JEMBATAN DC&AC dan APLIKASINYA
PENDAHULUAN • Sirkuit jembatan biasanya digunakan untuk mengukur nilai komponen, seperti resistansi, induktansi, kapasitansi dan parameter sirkuit lainnya • Keakurasiannya sangat tinggi
Wheatstone bridge [CONTENTS] • Photograph of the instrument • Simplified schematic of the bridge circuit------------------
Operasi dasar • Measurement errors : • Found in the limiting errors of the three known resistors • Insufficient sensitivity of the null detector • Changes in resistance of the bridge arms due to the heating effect of the current through the resistors • Thermal emfs in the bridge circuit or the galvanometer circuit (when low-value resistors are being measured) • Errors due to the resistance of leads and contacts exterior to the actual bridge circuit
Thevenin Equivalent Circuit • Wheatstone bridge configuration -------------------- • Thevenin resistance looking into terminals c and d -------- • Complete Thevenin circuit, with the galvanometer connected to terminals c and d
The Thevenin, or open circuit voltage : • The Thevenin resistance : • The galvanometer current :
Kelvin Bridge • Wheatstone bridge circuit, showing resistance Ry of the lead from point m to point n • Basic Kelvin double bridge circuit --------------------------
Loop Tests with The Portable Test Set • Murray-loop test, used for locating a ground fault (short circuit) ----------------------------- • Varley-loop test: (a) no.1; (b) no. 2; (c) no.3, used to locate grounds, crosses, or short circuits in multiconductor cable • (b)
Guarded Wheatstone Bridge • Used for high resistance measurements
Comparison Bridges • Capacitance comparison bridge • Equating the real terms : • Equating the imaginary terms : • Inductance comparison bridge
Inductance comparison bridge with extended measurement range • With the switch in position 1 : • With the switch in position 2 :