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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 - PowerPoint PPT Presentation
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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
1
23 RR
RRx
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 :
42
2
31
1
RRR
RRR
EEcd
42
42
31
31
RRRR
RRRR
RTH
gTH
THg RR
EI
Kelvin Bridge
• Wheatstone bridge circuit, showing resistance Ry of the lead from point m to point n
• Basic Kelvin double bridge circuit --------------------------
32
1 RRR
Rx
2
13 RR
RRx
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)
BABll x
2
22
1R
X
Guarded Wheatstone Bridge
• Used for high resistance measurements
General Form of The AC Bridge
3241 ZZZZ
3241
Comparison Bridges
• Capacitance comparison bridge• Equating the real terms :
• Equating the imaginary terms :
• Inductance comparison bridge
1
2
RR
RR sx
2
1
RR
CC sx
1
2
RR
LL sx
1
2
RR
RR sx
• Inductance comparison bridge with extended measurement range• With the switch in position 1 :
• With the switch in position 2 :
1
2
RR
rRR sx
rRR
RR sx 1
2