Dc Crompton Potentiometer Pdf
The slide-wire type of potentiometer described in the previous article is not a practical form of construction. The long slide wire is awkward, and even for the length shown cannot be read to a very great degree of precision.
Dc Crompton Potentiometer
Modern laboratory type potentiometers use calibrated dial resistors and a small circular wire of one or more turns, thereby reducing the size of the instrument. The circuit of a simple laboratory type potentiometer is shown in the below figure.There is one dial switch with fifteen steps, each having a precision resistor.There is also a single turn circular slide wire. For the case shown, the resistance of slide wire is 10 Ω and the dial resistors have a value of 10 Ω each. Quickbooks enterprise 16 activation code.
Dc Crompton Potentiometer Pdf File. Potentiometers: DC Electric Circuits Worksheets. Notes: It has been my experience that students require much practice with circuit analysis to become proficient. CLASS NOTES ON ELECTRICAL MEASUREMENTS & INSTRUMENTATION 2015 2 DISCLAIMER. Potentiometers: DC Potentiometer, Crompton potentiometer, construction, standardization, application. AC Potentiometer, Drysdale polar potentiometer; standardization, application. MODULE-III (10 HOURS).
Thus the dial has a total resistance of 150 Ω and in addition, the slide wire has a resistance of 10 Ω.The working current of the is 10 mA and therefore each step of dial switch corresponds to 0.1 V. The slide wire is provided with 200 scale divisions and since the total resistance of slide wire corresponds to a drop of 0.1 V, each division of slide wire corresponds to 0.1/200 = 0.0005 V. It is quite comfortable to interpolate readings upto 1/5 of a scale division and therefore with this potentiometer it is possible to estimate the readings upto 0.0001 V. The single-range shown above is frequently constructed to cover a range of 1.6 V - though, of course, it can be designed for any desired within reasonable and practical limits.For example, a Crompton's potentiometer is designed to measure voltages up to 1.9 V by simply adding three more resistance steps to the main dial. The circuit of a single potentiometer may be modified in a simple way to add a second range, which is usually by a second factor, such as 0.1 or 0.01, in order that the direct reading features of the original circuit may still be utilised. The design of circuit of a duo-range potentiometer should be such that it is possible to change the measuring ranges without re-adjusting the rheostat or changing the value of working of the battery.
This is essential so that once the instrument has been calibrated on x 1 range, calibration of the x 0.1 range is not necessary.The above requirement means that the E ac in above figure remains the same for both positions of range switch S.This condition is satisfied only when the total battery current has the same value for each measuring range. Precision Type Potentiometers. This potentiometer uses the Kelvin Varley arrangement shown below. However, in this, there are three measuring dials.The first dial measures upto 1.5 V (on the XI range) in steps 0.1 V: the middle dial has 102 studs and reads upto 0.1 V in steps of 0.001 V; the third dial also has 102 studs and reads from - 0.0001 V to 0.001 V in steps of 0.00001 V (i.e., 10 µV).There is no slide wire.The resistances of the middle dial shunt two of the coils of the first dial.
The moving arm of middle dial carries two arms spaced two studs apart. In actual practice the resistance of the second dial is greater than that between two studs in the main (first) dial, so that the voltage drop across the second dial is greater than 0.1 V.If this is not done the voltage drop in switch contact resistances and leads would render the converge of middle dial to less than 0.1 V. The third dial is obtained from a shunt circuit which permits a true zero and a small negative setting to be obtained.
Dc Crompton Potentiometer Pdf
Duo range vernier potentiometer. Xforce keygen 2016 autodesk. The vernier potentiometer reads to the increment of 0.00001 V (10 µV) on range XI and has the readability of 1 µV on x 0.1 range.
If a third range of x 0.01 is provided, the readability becomes 0.1 µV.This does not mean, unfortunately, that small voltages can be read with assurance to 0.1 µV. Measurements are subject to stray thermal and contact s in the, galvanometer and the measuring circuits. These EMFs may be of the order of one to several micro volts and are difficult to locate and control.These EMFs can be minimised only by special construction i.e., proper selection of metals for resistors, terminals and connecting leads and also by the use of thermal shields.
Standard Cell Dial Potentiometer. All modern incorporate a separate standard cell dial circuit (calibrating circuit). This provides a means of standard cell balance resistance to suit the value of the particular standard cell used.Also, a separate standard cell dial permits the operator to check the standard cell balance at any time during the course of measurement without disturbing the potentiometer setting. The figure below shows a separate standard cell dial incorporated in a single range potentiometer.This potentiometer is provided with an independent standardising circuit AD which can be set on any range of standard cell emf from 1.016 V to 1.020 V.A drop of 1.016 V is provided by resistance Rs and the remaining drop of 0.004 V is provided by the slide wire AC.Thus a considerable change in standard cell emf owing to temperature changes can be allowed for the operation of the circuit below. The slide wire of the calibrating circuit is set to read the emf of the standard cell which is connected to the.The selector switch S is put in the calibrate position and the rheostat is adjusted so that there is no current flowing through the galvanometer.This fixes the working current to its proper value.The switch S is then thrown to the operate position and unknown is read by adjusting the measuring circuit dial and slide wire. Single range potentiometer using independent calibrating circuit.