Two Probe Method For Resistivity Measurement OF Insulators

The Two Probe Method is one of the standard and most commonly use 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.

DESCRIPTION OF THE COMPLETE EXPERIMENTAL SET-UP

 Two Probes Arrangement

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 a suitable stand, which also holds the sample plate and RTD sensor. The stand also serves as the lid of PID Controlled Oven. Teflon coated leads are provided for connecting with High Voltage Power Supply EHT11 and Digital Pico Ammeter. With this set-up assuming max. Voltage = 1500V; current 10x10-¹² A
(max) and thickness of sample 1mm.

The resistivity of the sample could be measured upto 14 10 ohm. cm

PID Controlled Oven

The unit is a high quality PID controller wherein the temperatures can be set and controlled easily. The P, I and D parameters are factory set for immediate use, however, the user may adjust these for specifies applications as well as auto-tune the oven whenever required. The steps for these are given in the usermanual. Although the controller may be used either
for our small oven, up to 200°C or a larger oven up to600°C, however, in the present setup only small oven (provided) is to be used. The controller uses thermocouple as temperature sensor.

Specification of the oven controller

Temperature Flange : Ambient to 200°C

Display Accuracy : ±0.3°C

Setting Type : Front push buttons

Control Method : PID, PIDF, PIDS

Measurement Accuracy : ±0.5°C (typical

Oven : Specially designed for Two Probe Set-Up

Sensor : Thermocouple Chromel-Alume)

Display : 7 segment LED, two rows

Values : Process Value, PV and Set Value, SV

Power : 150W

High Voltage Power Supply

This power supply is designed to meet the power requirement – where a high voltage source with high degree of regulation & stability is required. 

Digital Picoammeter

 Multiplier X1, X10, X10 , X10 , X10 , X10

Resolution 1pA, 10pA, 100pA, 1nA, 10nA, 100nA

Accuracy 0.2% for all ranges

Stability Within ± 1 digit

Input Resistance 2.5KΩ, 0.25KΩ, 25Ω, 0.25Ω, 0.025Ω

Display 3½ digit, 7 segment LED (12.5mm height) with auto polarity and decimal indication

Input Through amphenol connector

Power Supply 220V ± 10%, 50Hz