Methods of Measuring Electrical Resistance (Google eBook)

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McGraw-Hill book Company, 1912 - Electric resistance - 389 pages
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Contents

Voltmeter Method Circuit Includes a Known Resistance Method II
23
Comparing Potential Drops with a Deflection Instrument Special Case
24
Voltmeter Method Using a Shunt
26
Deflection Method Resistance Measured by Substitution
27
Voltmeter Method Circuit Forms Loop of Three Unknown Re sistances Two of which are to be Determined
30
Limitations of Voltmeter Methods
34
Resistance Measured with a Voltmeter and an Ammeter
35
Remarks Upon the Methods of Chapter II
37
Ohmmeters and Meggers
38
Null Methods Resistance Measured by Differential Instruments 300 Remarks on Null Methods
40
Properties of Differential Circuits
41
Illustration of the Practical Advantages of Differential Circuits
45
Differential Galvanometer Used with Shunts
48
The Differential Telephone
50
The Wheatstonebridge Network Slidewihbbkidge Methods Aet Pae 400 Network of the Wheatstone Bridge
51
Uses of the Slidewire Bridge
54
Comparison of Resistances by Modified Slidewire Bridge
58
The CareyFoster Method
61
Galvanometer Resistance Measured Using the Second Prop erty of the Bridge
69
Calibration of Bridge Wire
70
The KelvinVarley Slides
75
Wheatstonebridge Methods Variable Rheostat Arrangements of Resistances Per Cent Bridge Suggestions for Using Bridge 500 Wheatstonebridge Met...
78
Arrangements of Resistances in Wheatstonebridge Rheostats
79
Rheostat Coils Classical Arrangements
81
Northrups Fourcoil Arrangement
82
Fivecoil Combinations
86
Decade System of Feussner
87
Arrangements of Resistances for the Ratio Arms of Wheatstone Bridges
89
Schones Arrangement of Ratio Arms
91
Nonreversible Ratio Arms Adjustable without Contact Resistances
92
Wheatstone Bridge Arranged for Reading in Per Cent
93
Remarks upon the Use of the Wheatstone Bridge
94
The Measurement of Low Resistance 600 Introductory Statement
100
Low Resistance Measured with an Ammeter and a Millivolt meter
101
To Measure the Resistance of Sections of a Closed Circuit General Method
102
To Measure the Resistance Between Two Points on a Busbar
106
Measurement of the Current in a Busbar
108
Measurement of the Resistance of Underground Mains
110
Comparison of Low Resistances by the Modified Slidewire Bridge
114
Comparison of Low Resistances with a Potentiometer
115
Theory of the Kelvin Double Bridge
117
Art Page 611 Sensibility Which Can be Obtained With the Kelvin Double Bridge
120
Methods of Applying the Kelvin Double Bridge Principle
123
Plan of Procedure for Making and Recording a Measurement
126
Sample of a Lowresistance Measurement Resistivity of Mag nesium
127
The Determination op Electrical Conductivity
130
Standards of Conductivity Their Relation Useful Formula
132
The Measurement of Conductivity
140
The Hoopes Bridge Operations Required for Using
143
Precautions to Observe in Using Hoopes Bridge
144
Other Methods of Measuring Conductivity
145
Method of Using Variable Resistance Standard for Conductivity Determinations
147
Method of Calculating Conductivity from Resistance Data
148
Conductivity Determinations with Fixed Resistance Standard and Variable Ratios
150
The Measurement of High Resistance 800 High Resistance Specified and Described
152
Wheatstonebridge Method of Measuring a Resistance from 10 to 1000 Megohms
153
Use of a Capacity in Connection with a Wheatstone Bridge for Highresistance Measurements
155
Major Cardews Electrometer Method of Measuring a High Re sistance
156
The Measurement of High Resistances Unassociated with an Appreciable Capacity Deflection Methods
157
The Ayrton or Universal Shunt
160
Galvanometer Constant Obtained by Using an Ayrton Shunt
166
Factory Testing Set for Insulation Measurements
198
Directions for Using and Test of Method
207
Determination of the Internal Resistance of Batteries
214
Voltmeter and Ammeter Methods of Measuring the Internal
220
Alternatingcurrent Methods of Measuring the Resistance of
226
Galvanometer Deflection Methods for Obtaining the Resistance
233
Kelvins Method
235
SiemensMethod
236
Resistance of Electrolytes
238
The Method of Kohlrausch for Measuring the Resistivity of an Electrolyte
240
Determination of Relative Resistivities of Electrolytes
244
Herings Liquid Potentiometer Method for Determining Elec trolytic Resistances
247
The Substitution Method
248
Elementary Principles of Fault Location 1200 Fault Location
251
Faults Occurring on Land Lines
252
Problems in Fault Location
253
Loop Methods for Locating Grounds or Crosses
258
Notes on the Varley Test
265
Modified Loop Methods to Meet Special Conditions
267
Where the Faulty Wire is of Known Length and there is Only One Good Wire of Unknown Length and Resistance
271
One Good Wire of Unknown Length and Two Faulty Wires Equal in Length and Resistance
276
Methods of Applying Corrections in Loop Tests
278
Location of Grounds on Hightension Cables
281
Location of Faults upon Lowtension Power Cables
283
Method of Locating Grounds upon Heavy Short Underground Cables
284
Location of Inductive Crosses
288
Comments on Practice and Accuracy in Fault Location
290
A Word on Faultlocating Apparatus
293
Measurement of Temperature by the Measurement of Resistance 1300 Remarks on Temperature and Thermometry
296
Electricalresistance Thermometry
297
Construction of Resistance Thermometers
302
Methods of Reading Resistance Thermometers
308
Differentialgalvanometer Method
312
Use of Dial Bridges for Temperature Measurements
314
Art Page 1308 Kelvin Doublebridge Method of Reading Temperature
315
Directdeflection Method of Reading Temperatures
317
Deflection Methods Using Constant Currents
319
The Measurement of Extremely High Temperatures
322
Instruments Used for Measuring Resistance Some General Principles Considered 1400 Proposed Treatment of Subject
324
Sensibility and Accuracy 32 5
325
Resistance Standards
326
Resistance Boxes and Wheatstone Bridges General Remarks
331
Watt Capacity of Resistance Units
332
Construction of Resistance Spools
333
The Precision of Coils in Resistance Sets
334
Some Features of Outside Construction
335
Deflection Instruments and Galvanometers l r00 Distinction Between Indicators and Deflection Instruments
338
Pointer Type Flatcoil Galvanometers
340
Sensitive Galvanometers for Refined Measurements of Resistance anil Insulation Testing
346
Comparison of Galvanometers
349
Description of One Type of Highsensibility Galvanometer
361
Table 1 Values of tKKa_a
363
Mathematical Quantities and Relations 1 Functions of ir and e
365
3 Formula for the Conversion of Temperature Scales
366
5 Relations Between Resistance and Conductivity
367
6 Conversions from Practical to Electrostatic to Electro magnetic Units C G S System
371
7 Approximation Formulae Certain other Expressions
372
Wire Data and Formulae 1 Wire Table
374
2 The Ohm
375
4 Certain Formula for Wire
376
Copyright

Common terms and phrases

Popular passages

Page 96 - The rule therefore for obtaining the greatest galvanometer deflexion in a given system is as follows : Of the two resistances, that of the battery and that of the galvanometer, connect the greater resistance so as to join the two greatest to the two least of the four other resistances.
Page 84 - ... are connected giving the value 0, if between the blocks 2 and 5, the points 2 and 5 are connected giving the value 1 and so on. The value 9 is obtained when the plug is disposed of by being inserted in the last pair of blocks which have no connections.
Page v - While it is not claimed that the work is exhaustive, the author has selected for presentation all methods which in his judgment are useful...
Page 294 - Fig. 367, which is wound in a circle and is about 100 ohms. By a special construction, it is arranged so that contact can be made at any point along it, and it is therefore equivalent to a high resistance wire. It has a moving contact C and a scale of 1000 divisions. In series with this, there are the two resistances E and R. E has exactly the same resistance as the wire AR.
Page 365 - By definition, n is the ratio of the circumference to the diameter of a circle (see Section ccc 14-L).
Page 207 - This ratio may take a value of two or more. It should be clearly understood just what is meant by the quantity R which this method measures. It is a quantity which, expressed in ohms and multiplied by the square root of the mean square value of the alternating current through the circuit, expressed in amperes, will give the square root of the mean square value of that component of the impressed emf expressed in volts which is in phase with the current. Or, it is the quantity which, when multiplied...
Page 84 - Fig. 503b shows the method of connecting these points two at a time, with the use of a single plug. The circles in the diagram represent two rows of ten brass blocks each. To the first two blocks at the top of the rows, the points 5 and 1...
Page 83 - If the points (2) and (5) are connected the 3, 31 and 2 ohm coils will be short circuited and the current will traverse 1 ohm. By extending this process so that we connect two and only two points at a time, it is possible to obtain the regular succession of values n (0, 1, 2, 3, 4, 5, 6, 7, 8, 9), the last value being obtained when no points are connected. The following table shows the points which must be connected to obtain each of the above values and the coils which will be in circuit for giving...
Page 332 - ... volts and the b' terminal at 220 volts; thus the current in the AL coil, which in this case is the magnetizing current of the core, is due to a potential difference of 20 volts. The strength of this current will be found by Ohm's law, namely the quotient of the EMF, or difference of potentials between the terminals of the coil, divided by the resistance of the coil in this case = -ffa, that is T\j- ampere.
Page 297 - ... Extending the investigation to solutions of cadmium sulphate we obtain a cell in which the heat of dilution is relatively large. The study of this cell was taken up in the general manner just described. The amalgam, however, proved more troublesome. With dilute amalgams, the EMF did not consistently return to the same value when brought back to the same temperature. Evidently some change had taken place either in the amalgam or the electrolyte. Since there is no transition point in cadmium sulphate...

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