Kelvin–Varley divider

Kelvin Varley voltage divider is in the electrical circuitry is a form of a voltage divider which can be adjusted in steps by a switch and is composed of resistor networks with fixed resistance values. The type of construction allows for a reproducible setting of the values ​​of the voltage divider ratio, which is not possible with the use of potentiometers. Applications are that control the switch of the voltage divider electronically in the electrical metrology and equipment. Commercial Kelvin - Varley voltage divider for the manual application have at each stage on a decadal classification for digital controlled electronic measuring systems is a binary classification usual.

Construction

Kelvin Varley voltage divider represents a cascaded form of individual voltage divider, each stage represents exactly one point of the voltage divider ratio, and thus can be reproducibly adjusted independently of the other locations by means of tap changers. In the picture is a decadal Kelvin - Varley voltage divider with four decimal places () with a set Spannungssteilerwert

Shown. The divider value is true if the output is high impedance load, the current drawn over the cross current in the voltage divider is negligibly small.

Each stage consists of several Fixwiderständen same value which have taps between the resistors are used for switching. In the execution of the decadal -th stage is, until the final stage, from 11 resistors, the last stage has only 10 resistors. The ratio of the resistance values ​​between two adjacent stages and is in the decadal design value of 5, that is, the resistance values ​​increase per level by a factor

From. The input resistance has a value in the adjacent circuit 100 k.

The difficulty in circuit design is that the odds of one stage must have the same value and the balance of 11 and 10 resistors is impractical on a value. Practically constructed Kelvin Varley voltage divider therefore have additional adjustment elements in the form of individual adjustable for calibration potentiometers per stage and adapted thereto topology.