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Four Probe Setup Research Model Experiments for Physics Lab for High School Science Kits Lab Manufacturers, Suppliers & Exporters in India
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Naugra Export, are top Four Probe Setup Research Model Experiments for Physics Lab for High School Science Kits Lab manufactures in India, along with our full range for High School Science Kits. Ideal for industrial training, classroom demonstrations, curriculum-based experiments, and laboratory practical, it combines rugged construction with reliable performance, built for bulk tender supply worldwide. Manufacturers of Four Probe Setup Research Model Experiments for Physics Lab for High School Science Kits Lab in India and Trusted Supplier for OEM Suppliers around the globe. Full specifications are listed below.
Full specifications for the lab product:
Four Probe Setup Research Model Experiments for Physics Lab - The Four
Probe Method 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, the arrangement is also specially useful for quick
measurement on different samples or sampling different parts of the
sample.
Description of the experimental setup
1. Probes Arrangement
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 suitable stand, which also hold the
sample plate and RTD sensor. This stand also serves as the lid of PID
Controlled Oven. Proper leads are provided for the current and voltage
measurement.
2. PID Controlled Oven
This is 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 (PWM) 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
Temperature Range Ambient to 200° 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 Four Probe Set-Up
Sensor RTD (A class)
Display 3½ digit, 7 segment LED with autopolarity and decimal
indication
Power 150W
3. Constant Current Source
a) Constant Current Source, Model : CCS-01 (for low resistivity to
medium resistivity samples)
It is an IC regulated current generator to provide a constant current to
the outer probes irrespective of the changing resistance of the sample
due to change in temperatures. The basic scheme is to use the feedback
principle to limit the load current of the supply to preset maximum
value. Variations in the current are achieved by a potentiometer
included for that purpose. The supply is a highly regulated and
practically ripples free d.c. source. The constant current source is
suitable for the resistivity measurement of thin films of metals/ alloys
and semiconductors like germanium.
Specifications
Open Circuit Voltage 12 V
Current Range 0-20mA & 0-200mA continuously variable
Resolution 10µ A at 0-20mA range
Accuracy ± 0.25% of the reading ±1 digit
Display 3½ digit, 7 segment LED with autopolarity and decimal
indication
Load Regulation 0.03% for 0 to full load
Line Regulation 0.05% for 10% changes
b) Low Current Source, Model : LCS-02 (for high resistivity samples)
Low Constant Current Sources are needed when the sample resistance,
either inherently or due to contact resistances, is large. These include
the resistivity measurement of silicon wafers or high resistivity film
deposits. Large values of the sample resistance make the measurement
prone to noise pick-up from the mains and elsewhere. This is one of the
most significant problems of high resistance measurement.
In the present unit the problem of pick-up has been reduced to very low
levels by having a battery operated source. Since the current
requirement is small and the circuit being specially designed for this
purpose, the batteries should have a reasonably long life. Further, a
transistor circuit has been preferred over an Op-Amp based circuit as it
offers a reduction of the battery count and is also simpler. An
internal voltage reference of 2.5 volt ensures reliable operation even
when the batter voltage falls and a ten turn potentiometer makes the
current adjustment very easy. The actual current is read on a 3½ digit
LCD display. There are four current ranges which may be slected with the
help of a bandswitch on the panel.
Specifications
Open Circuit Voltage 15V (min.)
Current Range 0-2µA, 0-20µA, 0-200µA, 0-2µA
Resolution 100nA at 0-100µA range
Accuracy ± 0.25% of the reading ± 1 digit
Display 3½ digit, 7 segment LCD with autopolarity and decimal
indication
Load Regulation 0.05% for 0 to full load
Power 9V batteries
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