Portable Wheatstone Bridge
The bridge is extremely useful for resistance measurements with a fair egree of precision.
General : This bridge is fully portable with a built-in-sensitive Galvanometer and a dry battery.
Series Arm : There are 4 decades of 10 x 1, 10 x 10, 10 x 100 and 10 x 1000 ohms.
Range Multipliers : A single rotary switch furnishes 7 ranges multipliers of x 1000, x 100, x 10, x 1, x 0.1, x 0.01 and x 0.0001.
Range of Measurement : 0.001 ohm to 11.1 meg-ohms.
Battery : A dry battery of 4.5 volts is built-in. Provision is there for using external battery for measuring high resistances.
Galvanometer : Students galvanometer of M.O. 65 model, and of sensitivity 10 microamperes/div. is used.
Push Buttons : Two push buttons for battery and galvanometer are provided.
Accuracy : Both series and ratio coils are adjusted to an accuracy of better than 0.05%
overall Accuracy of measurements is better than ±0.1%.
a) Constantan Coil : Constantan Coil which are non-inductively wound, aged and properly varnished. Accuracy ±0.1%.
b) Manganin Coil : Manganin Coil which are non-inductively wound, aged and properly varnished. Accuracy ±0.02%.
Portable Wheatstone Bridge (Modified) with Varley & Murray Loop Test
This bridge is exactly same as no. 241 except for additional facility of murray and varley loop tests for location of faults in cables. The bridge is suitable for resistance measurements also.
For resistance measurements and varley loop test, there are 7 multiplying factors of x 1000 , x 100, x 10, x 0.1, x 0.01, x 0.001.
For murray loop tests, 3 additional multiplying factors fo 10M, 100M and 1000M are provided.
Special switching arrangement has been provided to caryy out conductance tests, varley loop test and murray loop test.
Rest of the features like series arm, battery, galvanometer, push bottons are same as no. 241.
a) with Constantan Coil b) with Manganin Coil
NOTE : Also called electrical fault localiser or line tester.
Crompton Potentiometer Voltage Dials :
Ist Dial 6x250mv = 1500 mv
2nd dial (slide wire) = 0250 mv
Total = 1750 mv
- Each slide wire division is equal to 1/2 milli volt or 500 micro volts
- Coarse and fine rheostats are provided. Terminals for
2-volts battery, Galvanometer, standard cell are provided
on the panel.
- Current is of the order of 125 mA.
Standardisation : Standardisation is carried out by actually setting the voltage dials equal to the standard call voltage.
Crompton Potentiometer
Same as above with a self standardisation circuit built in, which renders standardisation independent of setting of voltage dials.
Addition of Range Switch
For range switch (multiplier of 1/10) which gives the least count as 50 micro volts.)
INDUSTRIAL KELVIN DOUBLE BRIDGE
Industrial Kelvin Double Bridge
Standard Resistance : There are 10 coils of 0.01 ohm each arranged on a rotary dial plus a circular slidewire of total resistance 0.01 ohm and 500 sub-divisions. Each sub-division is equal to 0.00002 ohms on the normal range.
Multiplying Ratios : A rotary switch furnishes 5 multiplying ratios of x 100, x 10, x 1, x 0.1 and x 0.01.
Range of Measurement : The bridge has a range of 0.2 micro ohm to 11 ohms.
Range Multiplying Least Count
2 Milli W to 11 W x100 2 Milli W
0.2 Milli W to 1.1 W x10 0.2 Milli W
20 Micro W to 11 W x1 20 Micro W
2 Micro to .011 W x0.1 2 Micro W
0.2 Micro W to .0011W x.01 0.2 Micro W
Max. Current : 10 amperes intermittently and 5 amperes continuously.
Terminals : Terminals for battery, galvanometer, current and potential terminals are all provided on the bakelite panel enclosed in a teak wood box.
Current Reversing Switch : A battery reversing switch is provided to reverse the current in the bridge to eliminate thermal effects.
Resistance Coils : Manganin coils are used.
Accuracy : ±0.05% ±1 small division of the slide wire.
Industrial kelvin Double Bridge
Rest specifiacations are same as ABOVE but with an additional range factor of x1000 to give the range of measurement as 0.2 micro ohms to 110 ohms.
ACCESSORIES OF INDUSTRIAL KELVIN BRIDGE
Adjustable heavy duty D.C. Current Source
The unit is mains operated and can deliver a continuously adjustable D.C. Current of 0-10 Amp. maximum.
The unit consist of a variac, a step down transformer, a bridge rectifier, filter, circuit and an ammeter of 0-10 amp. to read current.
Two heavy brass terminals are provided for output.
Input voltage : 230 Volts A.C. mains 50 c/s
D.C. output : Approximate 0-10V , Continuously adjusted to give a variable current of 0-10 Amp. depending upon external load.
Conductivity Attachment
It is arrangement to hold specimens in the form of wires, rods strip etc. separate current & potential temrinals are provided. Distance between potential point is 500mm. It can hold specimen of any size between 1/2" dia rod to 42 S.W.G. wires.
Different type of 4 Arms Bridges
These experiments are compiled in wooden cabinet and panel of an Hylem sheet, circuit diagram engraved on panel, Variable Resistor are non inductive type switched by rotary switches, Important connection are brought on terminals complete with A.F. Oscillator TE-95 and Head Phone.
(1) Anderson Bridge
(2) Weins Bridge
(3) Desauty Bridge
(4) Schering Bridge
(5) Maxwell Bridge
(6) Hey's Bridge
(7) Owen's Bridge
(8) Wheatstone Bridge
