Four Probe Set-up (mapping)

We Offer Four Probe Method It is One of the Standard and Most Widely Used Method for the Measurement of Resistivity. in Its Useful Form, the Four Probes are Collinear. the Error Due to Contact Resistance, Which is Significant in the Electrical Measurement On Semiconductors, is Avoided By the Use of Two Extra Contacts (probes) Between the Current Contacts. in this Arrangement the Contact Resistance May all Be High Compare to the Sample Resistance, But as Long as the Resistance of the Sample and Contact Resistance's are Small Compared with the Effective Resistance of the Voltage Measuring Device (potentiometer, Electrometer or Electronic Voltmeter), the Measured Value Will Remain Unaffected. Because of Pressure Contacts, and 2 Way Motion, the Arrangement is Specially Useful for Quick Measurement On Large Samples At Room Temperature.
features
Easy Resistivity Mapping of Large Sample
2-way Movement with Vernier Scales (0.01mm)
Spring Loaded Contacts for Firm Connections
experiment Consists of the Following:
1. Probes Arrangement, Fpa-01
it 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 Probe Arrangement is Mounted in a Tube, Which also Provide Leads for Connections to Constant Current Power Supply and D.c. Microvoltmeter. the Tube Containing Four Probes is Mounted On a Travelling Microscope Type System, Scales and Verniers are Made of Stanless Steels with Following Specification:
horizontial: 20 Cm Least Count 0.001 Cm
laterial: 6 Cm Least Count 0.001 Cm
vertical: 15 Cm Least Count 0.001 Cm
the Bed is of Heavy Casting, Thoroughly Aged and Machined, is Fitted with Leveling Screws. a Large Platform is Provided for Fixing the Sample.
2. Constant Current Source
a) Constant Current Source, Model : Ccs-01
(for Low Resistivity Samples)
the Current Source is Suitable for the Resistivity Measurement of Low to Medium Resistivity Samples such as Thin Films of Metals Alloys and Semiconductors like Germanium.
specifications
open Circuit Voltage: 12v
current Range: 0-20ma, 0-200ma
resolution: 10micro Ampere
accuracy: +-0.25% of the Reading
display: 3.5 Digit, 7 Segment Led
load Regulation: +-0.1% for 0 to Full Load
line Regulation: +-0.1% for 10% Changes
b) Low Current Source, Model : Lcs-02
(for High Resistivity Sample)
this Current Source is Especially Suitable for the Resistivity Measurement of Polymer Ceramics and Si Cryustals.
specifications
open Circuit Voltage: 15v
current Range: 0-2micro Ampere, 0-20micro Ampere, 0-200micro Ampere & 0-2micro Ampere
resolution: Ina At 0-2μa Range
accuracy: +-0.25% of the Reading ±1 Digit
display: 3.5 Digit, 7 Segment Lcd with Autopolarity
load Regulation: +-0.1% for 0 to Full Load
power: 3 X 9v Batteries
3. D.c. Microvoltmeter, Dmv-001
the Experiment Complete in all Respects.