The Wheatstone Bridge Instrument

Chapter 2.9 The Wheatstone Bridge Instrument

Fundamental Electrical and Electronic Principles Third Edition Book
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Fundamental Electrical and Electronic Principles Third Edition Book

  • D.C. Circuits 63 and now using equations [3] and [4] we can eliminate I 2 as follows: 111110223024084604 023233IIIII………………………[][] and A voltso, VII3330400 02440 02448095111...VRVBDBD Ans (b) For balance conditions RRR RRRRRR245452420204111 ohmso, Ans 2.9 The Wheatstone Bridge Instrument This is an instrument used for the accurate measurement of resistance over a wide range of resistance values. It comprises three arms, the resistances of which can be adjusted to known values. A fourth arm contains the ‘ unknown ’ resistance, and a central limb contains a sensitive microammeter (a galvanometer or ‘ galvo ’ ). The general arrangement is shown in Fig. 2.30 . Comparing this circuit with that of Fig. 2.27 and using equation (2.12), the value of the resistance to be measured ( Rx ) is given by RRRRxmdv ohm(I1 I3)(I2 I3)10Ω2ΩR1R38ΩR2R55ΩCAI1I210 VI3DBR420ΩE Fig. 2.29