Four Probe Experiment

Description of the experimental setup 1. Probes ArrangementIt has four individually spring loaded probes. The probes are collinear and equally spaced. The probes are mounted in a teflon bush, which ensure a good electrical insulation between the probes. A teflon 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. 2. SampleGermanium crystal in the form of a chip 3. OvenIt is a small oven for the variation of temperature of the crystal from the room temperature to about 200°C (max.) 4. Four Probe Set-up, DFP-02The set-up consists of three units in the same cabinet. (i) Multirange Digital VoltmeterIn this unit, intersil 3½ digit single chip A/D Converter ICL 7107 has been used. It has high accuracy like auto zero to less than 10mV, zero drift of less than 1mV/°C, input bias current of 10pA max. and roll-over error of less than one count. Since the use of internal reference causes the degradation in performance due to internal heating, an external reference has been used. Specifications Range X1 (0-200mV) & X10 (0-2V) Resolution 100mV at X1 range Accuracy ±0.1% of reading ±1 digit Stability Within ±1 digit Input Impedance 1MW Display 3½ digit, 7 segment LED (12.5mm height) with auto polarity and decimal indication Overload Indicator Sign of 1 on the left & blanking of other digits We are majorly looking for queries from Madhya Pradesh, Chhattisgarh, Maharashtra, Orissa, Andhra Pradesh and Rajasthan.