Description

We offer Two Probe Method, it is one of the standard and most commonly used method for the measurement of resistivity of very high resistivity samples like sheets/films of polymers. The resistivity measurement of such samples is beyond the range of Four Probe Method.

The experimental Set-up consists of the following:  
1.  Two Probes Arrangement, TPA**1
It has two spring load contact probes. These probes move in a pipe and are insulated by Teflon washers. This probes arrangement is mounted in suitable stand, which also hold the sample plate and RTD sensor. The stand also serves as the lid of PID controlled Oven. Teflon coated leads are provide for connecting with High Voltage Power Supply EHT**1 and Digital Picoammeter DPM***1. With the set-up assuming max. voltage = ***0V; current **0x****2 A (max) and thickness of sample 1mm. The resistivity of the sample could be measured upto ***4 ohm.cm.

2.  PID Controlled Oven, PID***0
This is a high quality temperature controlled oven suitable for Four Probe Set-up. The oven has been designed for fast heating and cooling rates, which enhances the effectiveness of the controller. While the basic design of the controller is around the PID configuration for its obvious advantages, wastage of power is avoided by using a Pulse Width Modulated (PMW) switch. This combination has the advantages of both on-off controller and linear PID controller. The result is a good stable and accurate temperature control.

Platinum RTD has been used for sensing the temperature. A wheatstone bridge and an instrumentation amplifier are used for signal conditioning. Feedback circuit ensures offset and linearity trimming to a great degree of accuracy. The set and measured temperature are displayed on 3½ digit DPM through selector switch.

Specifications of the Oven

Temperature Range: Ambient to **0°C
Resolution: 0.1°C
Short Range Stability: ±0.2°C
Long Range Stability: ±0.5°C
Measurement Accuracy: ±0.5°C (typical)
Oven: Specially designed for Two Probe Set-Up
Sensor: RTD (A class)
Display: 3½ digit, 7 segment LED
Power: **0W

3. High Voltage Power Supply, EHT**1

Output: *****0V continuously adjustable
Current: 1mA (max.)
Polarity: +ve or -ve, as required
Regulation: ±0.*5% for 0 to 1mA load
Stabilization: ±0.*2% for ±*0% mains variation
Display: 3½ digit, 7 segment LED DPM
Connection: Output through a amphenol connector on the front panel
Protection: Fully protected against overload and short circuit by current limiting technique
Power requirements: **0V ±*0%, *0Hz
Weight: 5Kg
Dimensions: **0mm X **0mm X **0mm.

4. Digital Picoammeter, DPM***1

Multiplier: X1, X*0, X**2, X**3 , X**4 , X**5
Accuracy: 0.2% for all ranges
Resolution: 1pA, *0pA, **0pA, 1nA, *0nA, **0nA
Input Resistance: 2.5K&branded;, 0.*5K&branded;, *5&branded;, 2.5&branded;, 0.*5&branded;, 0.**5&branded;
Display: 3½ digit, 7 segment LED (*2.5mm height) with  auto polarity and decimal indication.
Input: Through Amphenol connector.
Power Supply: **0V±*0%, *0Hz.
Weight: 2.5Kg.
Dimensions: **0mm X **5mm X **0mm.

The experimental set-up is complete in all respect.