pertemuan 9 jembatan dc&ac dan aplikasinya. pendahuluan sirkuit jembatan biasanya digunakan...
TRANSCRIPT
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 R
RRRx
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
RR
R
RR
REEcd
42
42
31
31
RR
RR
RR
RRRTH
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 RR
RRx
2
13 R
RRRx
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)
BA
Bll x
2
22
1
RX
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
R
RRR sx
2
1
R
RCC sx
1
2
R
RLL sx
1
2
R
RRR sx
• Inductance comparison bridge with extended measurement range
• With the switch in position 1 :
• With the switch in position 2 :
1
2
R
RrRR sx
rR
RRR sx
1
2