Educational Instruments

Approx. Rs 64,000 / PieceGet Latest Price

Approx. Rs 5.6 Lakh / PieceGet Latest Price

These instruments are used in contact angle measurement, surface free energy analysis, and surface or interfacial tension measurement.The V TECH (VT) series contact angle meters have a range of systems starting from DMs-200, which is the basic model, to the most sophisticated VT-701.The VT-200 model is used to determine contact angle using the sessile drop method in static mode.

From model VT-CE1, all instruments can determine contact angle using the sessile drop method in static mode as well as in dynamic mode. The surface tension of a liquid sample can also be determined. The robust FAMACS software ensures that the system can also give dynamic contact sessile drop method,extension/contraction method, surface or interfacial tension of liquids with pendant drop method,sliding method, and dynamic sliding method. This is the most automatic model and even stage movement and droplet deposition can be controlled through the PC.

Optional accessories are numerous to choose from including computer-controlled dispenser, sliding method, temperature control of stage, temperature control of dispenser, and high speed camera.With the surface free energy software, the solid surface free energies and their components from the results of contact angle with different liquids can be measured.If surface free energy is the main analysis, then there is also an option called surface energy kit which consists of five kinds of probe liquids and proper needles.

Applications

The contact angle meter has application in the pharma field, where the wettability of powders can be studied. The contact angle measurement gives remarkable data on wettability and thus pharma companies can use this tool in their analytical research and development. It can also be used to analyze the processes of coating, cleaning, and surface finishing in research institutes.

Approx. Rs 19,500 / PieceGet Latest Price

EC Specifications

EC Range 0 to 1999 S/cm, 0.0 to 199.9 mS/cm, 0.0 to 199.9 S/cm, 0.00 to 19.99 mS/cm

EC Resolution 0.1 S/cm, 1 S/cm, 0.01 mS/cm, 0.1 mS/cm

EC Accuracy (@25C/77F) +-1% FS (excluding probe error)

EC Calibration manual, one point

EC Temperature Compensation automatic, 0 to 50 DegreeC (32 to 122 DegreeF) with user- selectable coefficients between 0 to 2.5 %/ DegreeC

Resistivity Specifications

Resistivity Range 0 to 19.90 M-cm

Resistivity Resolution 0.10 M-cm

Resistivity Accuracy +-2% FS

Resistivity Calibration manual, one point

Resistivity Temperature Compensation automatic, 0 to 50 DegreeC (32 to 122 DegreeF) with

user-selectable coefficients between 2 to 7 %/ DegreeC

Additional Specifications

Electrode/Probe VT-HI76303 platinum four-ring conductivity probe with internal

temperature sensor, DIN connector and 1 m (3.3') cable (included); VT-HI3316D

resistivity probe with internal temperature sensor, DIN connector and 1 m (3.3') cable (included)

Environment 0 to 50 DegreeC (32 to 122 DegreeF), RH max 95% non-condensing

Power Supply 12 VDC adapter (included)

Dimensions 235 x 222 x 109 mm (9.2 x 8.7 x 4.3")

Weight 1.3 kg (2.9 lbs.)

Ordering Information HI2316 is supplied with VT-HI76303 conductivity probe,

VT-HI3316D resistivity probe, 12 VDC adapter, and instruction manual

Additional Information:

• Item Code: JL303

Approx. Rs 26,500 / PieceGet Latest Price

• Leakage-resistant surface
• Digital panel meter
• Constant current generator

Approx. Rs 71,250 / PieceGet Latest Price

We are suppliers of Heat Transfer in Natural Convection

The range of Experiment:

• To determine average heat transfer coefficient of Friction
• To calculate and plot variation of local heat transfer coefficient along the length of the tube

Specifications:

• Dia: 38 mm

• Length: 500 mm

• Nichrome Wire

• Temperature Sensors RTD PT100 type

• Digital Voltmeter: 0-300 Volt

• Digital Ammeter: 0-2 Amp

Approx. Rs 79,250 / PieceGet Latest Price

• To determine average surface heat transfer coefficient for a pipe losing heat by Forced Convection
• Comparison of heat transfer coefficient for different air flow rates and heat flow rates
• To calculate Reynolds number and Nusselt number for each experimental condition
• To plot surface temperature distribution along the length of the pipe

Approx. Rs 1,450 / PieceGet Latest Price

103 MM / 100 MM
103 MM / 100 MM

V-Tech offers FISCHER German-make Precision Hair Hygrometers,

Model no.112 with special hair, and Model no.221 with synthetic hairs, in 100 mm. dial

with fine workmanship quality, silver polished case, metal body, chromium-plated glass

bezel and polished dial with silver polish, calibrated and with side screw for adjustment,

measuring and indicating Relative Humidity, range 0-100 %.

They are used for environment control in labs, scientific research institutes, cold storage,

agricultural, nurseries, green houses, air-conditioned and computer rooms, meteorology,

textile mills, factories and in several other industries.

Approx. Rs 72,500 / PieceGet Latest Price

We are engaged in distributing Marshall Stability Test Apparatus that are widely used for measuring resistance to plastic flow of cylindrical specimen of bituminous pouring mixture loaded on the lateral surface. Offered apparatus is extensively used with a hot mixture containing tar or asphalt and average up to 25 mm maximum size. Customers can avail these apparatus from us in various specifications as per their needs and requirements.

Features:

• Highly durable

• Low maintenance

• Easy to use

• User-friendly

• Accurate results

Approx. Rs 34,500 / PieceGet Latest Price

• This Instrument is in according to VTECH D 1238, BS, DI, ISO, IS (Indian Standard) or according to customer’s required specification
• PID based temperature controller with auto-tune facility
• Having preset facility and buzzer output
• Applied weight manual

Approx. Rs 1.25 Lakh / PieceGet Latest Price

Approx. Rs 1,250 / PieceGet Latest Price

• This is used when the Optical Flat is less than 150 mm diameter. The Optical Flat is placed over the polished part under inspection. The light bands are viewed over the Optical Flat from above

• The part to be inspected is placed over the Optical Flat and the light bands are viewed from beneath after reflection from a mirror. This Type Monochromatic Light Source is used when the part under inspection is thin and of large diameter. If an Optical Flat of large diameter is to be placed on such thin parts there would be deformation of fringes due to the weight of large size Optical Flat. To avoid this the part to be inspected is placed over the Optical flat and the fringes are viewed after reflection from a mirror placed below.
• The Master surface of the Optical Flat face upwards and the test surface face downwards and are in contact to view the light bands. MLS-02 is suitable for use with 200 mm diameter Optical Flat. On request MLS to suit Optical Flats larger than 200 mm diameter is manufactured against specific Order.

Approx. Rs 28,500 / PieceGet Latest Price

The Flow Table is used to determine the flow of hydraulic cement, mortars and cement pastes. A test specimen is molded on the flow table to a specified volume and shape. Then, with the mold removed, leaving the test specimen on the table. The flow table is dropped and raised (via a hand crank or optional motor) a specified number of cycles, after which the flow (or increase in average diameter of the specimen) is measured. Motorized flow table with 10" (254mm) dia. cast-bronze table/platen and automatic digital counter. Motor stops automatically once a pre-set number of drops is achieved. Includes heavy-duty table/platen assembly, standard H-3622 cast bronze, 2.75" top dia. x 2" high x 4" bottom dia. cone mold, motor, and H-3614B counter. Designed to be mounted to concrete mounting block.

Order H-3624F, pedestal form and easily create your own mounting block for the flow table. Applications include: compression strength and air content tests of cement mortar; flow tests of hydraulic cement mortars; consistency tests of magnesium oxychloride cement; flexural strength test for bond strength or mortar to masonry units

Approx. Rs 99,500 / PieceGet Latest Price

• Robust measurements
• Digital readout
• Episcopic lighting

Specifications:

• Magnification: 10X
• Field of view: 30 mm
• Working distance: Contour: 65 mm
• Surface: 22 mm
• Illuminator: 24V, 150 W

Approx. Rs 5,950 / PieceGet Latest Price

Catering to the needs of the clients, we offer premium Searchlight. Our Searchlight is highly acclaimed in the market for its high luminosity. It makes use of Micro Processing advance Technology systems. Our Searchlight can be availed at market leading prices.

Special Features

• Easy-to-carry with molded handle and shoulder strap
• Reliable micro controller based design
• Low battery warning indicates exhausted battery
• High reliability MOSFET for solid state switching
• Selectable Continuous, timer and flasher functions
• Advance Low-Battery System
• Battery Cut-off system straight
• D.C. Fuse Blown
• Approx. 70 minutes ( ± 10 min) of constant use at full light and at full charge
• Rugged & weather resistant, molded Super Tough Glass
• Automatic low-voltage cut-off prevents deep discharge

Application Area

• Paramilitary Forces
• Defense Forces
• Police
• Air Ports
• Security Agencies
• Industries
• Fire Fighting
• Vital Installations

Visible Controls

• System on
• Advance Low-Battery System
• Battery Cut-off system straight
• D.C. Fuse Blown

Approx. Rs 52,500 / PieceGet Latest Price

• It consists of two concentric chambers, the inner chamber and the outer chamber, which communicates with each other through an opening at the top
• As the steam discharges through the metal basket, which has a large number of holes
• The water particles due to their heavier momentum get separated from the steam and collect in the chamber
• The comparatively dry steam in the inner chamber moves up and than down aging through the annular space between the two chambers and enters the Throttling Calorimeter

• It consists a narrow throat (Orifice)
• Pressure and temperature are measured by pressure gauge and thermometer
• The steam after throttling process passes through the heat exchanger and condensate is collected
• There is no need of boiler.

• To find the dryness fraction of steam

Approx. Rs 19,500 / PieceGet Latest Price

Approx. Rs 12,500 / PieceGet Latest Price

We are engaged in offering Under Vehicle Inspection Mirror. The Under Vehicle Inspection Mirror is made using high-grade material and we conduct stringent quality checks in order to assure their optimum quality. The Under Vehicle Inspection Mirror can be availed at market leading prices from us.

Features:

• High clarity
• Durable
• Excellent grip
• Adjustable lengths

• Weatherproof powder coated steel trolley with high density rubber wheels on ball bearings for smooth operation
• 24"x12" high quality toughened glass mirror which is cushion mounted to absorb shocks.
• Adjustable from 600mm to 850mm long.
• Heavy Duty "Eveready Commander" torch with high intensity beam and disposable D cells.
• (Including torch)

Approx. Rs 29,500 / PieceGet Latest Price

• The dial reading multiplied by spring factor gives the torque

• A container is also supplied complete with a set of springs
• One each of approx. 2 kg cm., 4 kg cm., 6 kg cm and 8 kg cm

• Frequency	50Hz
  Surface Finishing	Paint Coated
  Power Supply	230V
  Speed	5cm/min and 1 cm/min
  Briquettes cast	25.4 mm x 25.4 mm
  Testing Range	23Degree C to 27 Degree C

Approx. Rs 84,000 / PieceGet Latest Price

The Chemical oxygen demand i.e. COD value of water as determined by the dichromate method can be considered as an estimate of the theoretical oxygen demand means the amount of oxygen consumed into chemical oxidation of the organic constituents present in the water.

Features:

• Potassium Dichromate fast digestion - Spectrophotometric method
• Built-in & User defined calibration curve with the facility of storage.
• Unique plug-in standard SD card data storage technology
• Analysis of data can be transferred to the PC through SD card.
• Narrowband interface filters, cold light source extremely long lifespan.
• Fast accurate & stable performance.
• Auto Zero & Shut off facility
• Suppression of chloride interferences.
• Built-in real-time clock
• Various known brands COD vials can be used with the system

Specifications:

• Applications -used in practically every area of water analysis.
• as defined in IP 68, 1 hour at 0.1 meters, buoyant
• Description
• Scroll Memory
• Automatic Switch-Off
• Real-Time-Clock and Date
• Calibration mode indicator

Approx. Rs 43,950 / PieceGet Latest Price

Approx. Rs 1.98 Lakh / PieceGet Latest Price

Approx. Rs 59,500 / PieceGet Latest Price

Four Probe Method

Resistivity of Semiconductor by Four Probe Method at different temperatures

and determination of the Band-gap

The Four Probe Method is one of the standard and most widely used method for the measurement of resistivity of semiconductors. The experimental arrangement is illustrated. In its useful form, the four probes are collinear. The error due to contact resistance, which is specially serious 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 resistances 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 same sample.

Description of the experimental set-up

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 whole – arrangement is mounted on a suitable stand and leads are provided for the voltage measurement.

2. Sample

Germanium crystal in the form of a chip

3. Oven

It 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-02

The set-up consists of three units in the same cabinet.

(i) Multirange Digital Voltmeter

In 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 10μV, zero drift of less than 1μV/ °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 100μV at X1 range

Accuracy ±0.1% of reading ±1 digit

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

(ii) Constant Current Generator

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 ripple free d.c. source. The current is measured by the digital panel meter.

SPECIFICATIONS

Open Circuit Voltage : 18V

Current range : 0-20mA

Resolution : 10μA

Accuracy:

±0.25% of the reading

±1 digit

Load regulation:

0.03% for 0 to full load

Line Regulation:

0.05% for 10% changes

(iii) Oven Power Supply Suitable voltage for the oven is obtained through a step down transformer with a provision for low and high rates of heating. A glowing LED indicates, when the oven power supply is ‘ON’. The experimental set-upis complete in all respect

Typical results obtained from this set-up are shown in the figure.

Approx. Rs 98,500 / PieceGet Latest Price

Introduction

This experiment aims at measuring the charge of an electron and is perhaps the most basic of allatomic physics or modern physics laboratory experiments. It won Millikan the Nobal Prize in the year 1923.

The experiment depends on the ability to control, measure and balance very small force of the order 10-14N. The set-up consists of two horizontal parallel plates separated by about 5mm. The upper plate has a small hole through which microscopic oil droplets are sprayed in between the two plates with the help of an atomizer which is like a common perfume sprayer. These droplets get charged due to the frictional force during spraying. The free fall of these droplets in the space between the plates is observed in the gravitational field. A measurement of the velocity of fall along with the use of Stokes law leads to the calculation of the mass of the droplets and their radii if the oil density is known. These are of the order of 10-15kg and 10-6m respectively. By applying a potential difference between the plates, a uniform electric field is produced in the space between the plates. A measurement of the velocity of the negatively charged droplets rising in the electric field allows a calculation of the electric force on the droplets and hence the charge carried by them. In the experiment the droplets which rise and fall slowly are selected as they are expected to have a fairly small charge. These droplets are made to rise and fall several times. The repetitions of measurement of the velocities of rise and fall reduce the random error of their means. A fairly large number of droplets are observed and their charges are calculated. The analysis of the data on the total charge carried by the droplets shows that these total charges are integral multiples of a certain smallest charge which is the charge of an electron. This result also shows that the charge is quantized.The measurement of the charge on the electron can lead to the calculation of Avogadro’s number. The charge F (the Faraday) required to electro-deposit one gram equivalent of an element on an electrode during electrolysis is equal to the charge of the electron multiplied by the number of molecules in a mole. The Faraday has been found to be F = 9.625×10 7 coulombs per kilogram equivalent weight. Hence Avogadro’s number N = F/e.

Approx. Rs 42,500 / PieceGet Latest Price

Digital Readout with History Graph, PC InterfaceIf you have been thinking about getting a simple low-cost Geiger counter, search no more. Whether you are checking antiques, testing for safe granite countertops, evaluating your porcelain dishes and bathroom fixtures, or just monitoring soil, air, water, and food for radioactive contamination, this economically priced, a super-small device does it all. Small enough for your pocket or purse (5”x3”x1”), sensitive enough for background levels, and loaded with useful features…

• Classic Geiger counter clicking sound, which can be on or off
• Count per minute (CPM) or exposure rate microSievert/hr (µSv/hr) or (Mr/hr) readout
• Range: up to 65,535 CPM (200 microSv/hr or 20 mg/hr)
• Audible alarm with adjustable threshold
• Data logging, with date/time stamp (select every second, minute, or hour)
• USB PC interface and free simplistic software for real-time or delayed downloading and manipulation of your data (Windows XP/Vista/Win7 32 and 64 bits)
• Adjustable backlight and battery saving features
• Rechargeable 9V battery included (can also use Alkaline 9V)
• Useful indoors or out. Can be wall mounted and powered by AC adapter (or vehicle adapter) for continuous monitoring. Detects Beta and Gamma (0.1~1 MeV)

Get one before there is an emergency in your area. Great for home, work, or school environments. A nice educational tool as well.

Approx. Rs 49,500 / PieceGet Latest Price

MULTIPURPOSE

• A single device to analyze whole grains, flour, brans and other powdered products including semolina, couscous, and bulgur

• Wide range of pre-set calibrations included

• Multilingual interface Simplicity

• Results are generated in 60 seconds, no matter how many parameters are measured

• Self-adjusting measuring cell (wheat, corn, canola, flour)

• Export and use of results in Excel to simplify data processing Reliability

• Protection from dust and humidity

• Integrated cleaning system

• Results generated independently of temperature

• Storage of up to 100,000 saved analyses for permanent monitoring Reduced maintenance requirements

• User-serviceable, easy-to-change lamp

• Remote maintenance function, enabling V TECH Technologies to maintain the device remotely Modular design

Approx. Rs 12,500 / PieceGet Latest Price

This is very useful for distillation purpose for 300ml and 500ml capacity flask. Provided with condenser rack. To work on 220/230V A.C. Supply.

(a) Unit of 3 test Mantle Type (Without glass parts & clamps)

(b) Unit of 3 test Heater Type (Without glass parts and clamps)

(c) Unit of 6 test Mantle Type (Without glass parts & clamps)

(d) Unit of 6 test Heater Type (Without glass parts and clamps)

Approx. Rs 9,500 / PieceGet Latest Price

VT-03 Leak Tester is designed for the examination of the airproof property of packages, containers, bags, pipes. VT-03 package air proof tester is widely used in food, beverage, pharmaceutical, daily chemical, electrical and electronic industries, etc. VT-03 Leakage Tester complies with V-TECH D3078 and GB/T 15171 standards. The leak detection system is composed of the mainframe and the vacuum chamber. A test sample is placed in a vacuum chamber with water and the air above water level is evacuated by a venturi vacuum ejector. A great pressure difference is created inside and outside the sample and any slight leakage can be observed and identified when the sample is inflated.

Features

VT-03 Leak Tester uses vacuum ejector to generate stable vacuum environment. The state-of-the-art human-computer interface and PLC control unit on the leakage detection system make the parameter setting and test operation direct and easy. By saving different groups of parameters, users are free from the troubles of setting parameters each time before use. At the same time, different testing results and total test numbers can be saved to avoid any human errors.

• Leak test process all automatic
• Touching screen operation
• Digital vacuum degree and test time input
• Parameters and test data automatic saving
• Automatic vacuum maintenance and air back-flushing
• Extra-thick Perspex
• Different chamber sizes available
• No vacuum pump required
• Easy operation and maintenance

Approx. Rs 15,500 / PieceGet Latest Price

This Pan Evaporimeter is manufactured as per Is 5973: 1970.The Pan is manufactured from painted GI sheet tested for water leak proofness. The stilling well and thermometer clamps are manufactured from Brass. This is supported on the wooden platform and covered with reinforced chicken, Measuring Jar is manufactured from transparent Acrylic also available is bran.This Pan Evaporator is also available in galvanized Iron as per customer's requirement.

Approx. Rs 50,000 / PieceGet Latest Price

The outer chamber is made up of M.S. Sheet duly painted and inner chamber of thick

S.S. Sheet. The gap between two walls is fitted with high grade glass wool to avoid thermal loss. The plexi glass window makes it possible to inspect the specimen without disturbing the inner temperature. The lid of chest type unit is fitted with fluorescent tubes of 60 cms, Length, on the inner side.

The unit has a temperature range From 5°C. When the tube lights are ON temperature range is from 10°C to 50°C, A circulation fan is fitted to maintain temperature uniformity throughout. Cyclic illumination conditions are controlled by an automatic Timer (0-24) fitted to the unit. It is fitted with DIGITAL SPEED METER (RPM COUNTER) for shaking Platform having VARIABLE SPEED. The shaker has variable speed and a platform containing 16 flasks of 500ml or 40 flasks of 100 ml or 34 flasks of 150 mI capacity is supplied with the unit as standard accessory.

To work on 220/ 230 volts A.C. Supply.

(a) Temp. Range from 5°C above ambient to 50°C

(b) Temp. Range from 5°C

OPTIONAL ACCESSORIES

(a) Spare Shaking Platform.

(b) Additional non-shaking tray (Made of S.S.)

(c) Built-in U.V. germicidal tube light (Price for 2 nos.)

(d) Automatic Voltage Stabilizer 3.0 KVA (TRIPLE RELAY)

Approx. Rs 2.8 Lakh / PieceGet Latest Price

• Advanced technologies, WINDOWS operating system.
• Automatic restart after power failure
• Each thermal block has 4 independent temperature control sensors and 8 peltier heating units to ensure accurate and uniform temperature across block surface, and provide users with replicating previous condition set-up.
• 8" TFT color touch-screen with graphical display provides easy use for setting up and monitoring set parameter.
• The actual and target temperature can be viewed and displayed graphically in real time
• Built-in 11 standard program file template, can quickly edit the required files.
• Internal flash memory for 10000 typical PCR files in free configurable folders.
• Compatible woth mouse, keyboard, capable to transfer ata and perform software updates via USB Drive.
• Applicable with the following 0.2ml tube models: non-skirted, semi and fully skirted plated.
• Replacement module, dual - block module can simultaneously run two different PCR programs.

Additional Information:

• Item Code: VT-99121

Approx. Rs 22,000 / Piece(s)Get Latest Price

Designed for continues shaking of solutions in Erlynmeyer Flasks from 50ml to 1000ml capacity. It is compact bench type table top model with platform fitted with rubber discs mounted on ball bearing crank shafts to give an orbital motion to the flasks, within a diameter of approximately 2". The motor is coupled by means of a V-belt with pitch pulley, and is mounted on a heavy and sturdy angle iron frame. Speed is controlled by mechanical speed controller. To work in 220/230 volts A.C. Supply.

(a) DC MOTOR DRIVE with CONTINUOSLY VARIABLE ELECTRONIC SPEED REGULATOR in lieu of Mechanical Speed Control and A.C. motor.

Size : i) 45x45cm ii) 55x55cm iii) 65x65cm iv) 105x105cm v) 180x180cm

(b) Spare platform having any configuration other than the one supplied with the unit.

Size : i) 45x45cm ii) 55x55cm iii) 65x65cm iv) 105x105cm v) 180x180cm

(c) Microprocessor based Digital RPM counter

(d) Automatic 0-60 minutes "GERMAN" Timer.

Approx. Rs 2.15 Lakh / PieceGet Latest Price

Pure alkali halide crystals are transparent throughout the visible region of the spectrum. The crystals

may be colored in a number of ways

(1) by the introduction of chemical impurities

(2) by introducing an excess of the metal ion

(3) by X-ray, g-ray, neutron and electron bombardment

(4) by electrolysis

Colour centres produced by irradiation with X-rays

When a X-ray quantum passes through an ionic crystal, it will usually give rise to a fast photo-electron with an energy of the same order as that of the incident quantum. Such electrons, because of their small mass, do not have sufficient momentum to displace ions and therefore loose their energy in

producing free electrons, holes, excitons and phonons. Evidently these while moving near the vacancies form trapped electrons as well as trapped holes. The trapped-electron or trapped-hole centres so formed can be destroyed (bleached) by illuminating the crystal with light of the appropriate wavelength or warming it.

Thermoluminescence

Important information about the colour centres can be obtained by measuring the changes that occur when a coloured crystal is gradually heated. As the temperature is raised electrons and holes escape from their

traps at an increasing rate. The freed charges can recombine with each other or with other defects and give out luminescence by recombination.

The resulting thermoluminescence or ‘glow’ reaches maximum and then decreases to zero as the supply of trapped electrons or holes becomes exhausted. The plot of luminescence intensity verses temperature, taken

at a constant heating rate, is called the ‘glow curve’. It may contain one or many glow peaks, depending upon whether there are one or several different kinds of traps.

From the glow curve one determine the trap depth; the deeper the trap, the higher the temperature of the glow peak. A correlation between the temperature at which thermoluminescence occurs and the temperature at which particular band bleach can give valuable information about specific

centres. Typical results obtained from this set-up for

KCl crystal are shown in figure.

The experiment consists of the following

EXPERIMENTAL SET-UP FOR CREATING

THERMOLUMINESCENCE

(1) Sample: KBr or KCl single crystal

(2) Thermolumniscence Temperature Meter, TL-02

· Digital Thermometer

· Oven Power Supply

(3 Sample Holder

(4) Thermoluniscence Oven (0-423K)

(5) Black Box

FOR MEASUREMENT OF LUMINESCENCE

INTENSITY

(1) Photomultiplier tube: 931A

(2) PMT Housing with biasing circuit and coaxial cables etc.

(3) High Voltage Power Supply, Model: EHT-11

Output : 0-1500V variable (1mA max.)

Regulation : 0.05%

Display: 3½ digit 7-segment LED

(4) Nanoammeter, Model DNM-121

Range : 100nA to 100mA full scale in 4 ranges

Accuracy : 0.2%.

Display: 3½ digit 7-segment LED

Approx. Rs 24,500 / PieceGet Latest Price

Introduction

Regular arrangement of atoms in molecules and extended solids is very common. In crystalline solids the atoms are arranged in repeating three-dimensional arrays or lattices. Information regarding atomic bond distances and angles is fundamental to understanding the chemical and physical properties of materials. Since atomic dimensions are of the order of angstroms (10 m), unraveling the relative atomic positions of a solid requires a physical technique that operates on a similar spatial scale, Diffraction experiments involving X-ray, electron and neutron sources have therefore played a very crucial role in unraveling these structures. The significance of these experiments in science and engineering courses has been recognized. However, the cost of the equipment and the hazards associated with these experiments have made them very difficult to be

integrated and included in a teaching laboratory setting. The present set-up overcomes these limitations. An increase in scale by thousands from short wavelengths of X-rays to the long wavelengths of visible light, and by hundreds of thousands from an array of atoms in a crystal or an extended solid to an array of dots, allows us to replicate the basic features of a structural determination experiment in a teaching laboratory.

In place of Bragg diffraction whose results are to be simulated, we use Fraunhofer diffraction. Visible laser light passes through an array of scattering centers (dots) on a 35 mm slide. The diffraction pattern is viewed at

what is effectively infinite distance (a meter or so). This arrangement is capable of illustrating many of the essential features of the standard X-ray experiment. Mathematically, the equations for Fraunhofer and Bragg diffraction have a similar functional dependence on the interatomic distance, wavelength and the scattering angle. The symmetry of the diffraction pattern is same as the symmetry of the lattice causing the diffraction.

The central piece of the set-up is a slide (transparency) with eight (A-H) different arrangements of scattering

centers (dots) on different portions of the slide (Figure 3). The examples presented here serve to illustrate how the spacings, symmetries, spot intensities and systematic absences in a diffraction pattern are related to the lattice from which it is derived. Although these are two-dimensional lattices, they mimic what would be observed for diffraction from particular three-dimensional structures that are viewed in projection perpendicular to a face.