Four Probe Method

Consists of the following :

(a) Four Probe Setup, Model DFP -02

Constant Current Generator 

Open Circuit Voltage : 18V

Current Range : 0-20mA

Resolution : 10μA

Accuracy : ±0.25% of the reading ± digit

Display : 3½ digit, 7 segment LED (12.5mm) height

Load Regulation : 0.03% for no load to full load.

Line Regulation : 0.05% for ±10% of mains changes.

Digital Voltmeter

Range : 2000 mV

Resolution : 100μV at XI Range

Accuracy : ± 0.1% of reading ± 1 digit

Impedance : 1 Mohm

Display : 3½ digit, 7 segment LED (12.5mm) height ææwith decimal indication

Power Supply : 220V±10% 50 Hz

(b) Oven (up to 200 C) with a power supply

Oven Power Supply Suitable voltage for the oven is obtained through a step down transformer with a provision for low and high rates of heating. A glowing LED indicates, when the oven power supply is 'ON'. Small oven is used for the variation of temperature.

(c) Four Probe Arrangement

It has four individually spring loaded probes. The probes are collinear and equally spaced. The probes are mounted in teon bush, which ensure a good electrical insulation between the probes. A teon spacer near the tips is also provided to keep the probes at equal distance. The whole - arrangement is mounted on a suitable stand and leads are provided for the voltage measurement.

(d) Sample : ‘Ge’ Crystal