Abbe Refractometers

Refractometers are measuring instruments which put the phenomenon of light refraction (bending) to practical use. They are based on the principle that as the density of a substance increases (such as when sugar is dissolved in water), its refractive index rises proportionately. Refractometers were devised by Dr. Ernst Abbe, a German/Austrian scientist in the early 20th century. The prism in a refractometer has a greater refractive index than the sample solution. Measurements are read at the point where the prism and solution meet. With a low concentration solution, the refractive index of the prism is much greater than that of the sample, causing a large refraction angle and a low reading. The reverse (lower refraction angle and higher reading) would happen with a highly concentrated solution.
Abbe Refractometers are a type of refractometer used for measuring the refractive index of solid samples, such as glass, plastics and polymer films. There are two detection systems for refractive index: transparent systems and reflection systems. Hand-held refractometers and Abbe refractometers use transparent detection systems, and digital refractometers use reflection detection systems. Abbe refractometer readouts can be either digital or analogue. Abbe refractometers are used most often to measure solid samples – something that standard digital refractometers cannot do. Circulating water baths can be added to control instrument and fluid temperature in Abbe refractometers.
Newer versions of Abbe refractometers have recently been upgraded to include solid state Peltier elements to both heat and cool the refractometer so that you no longer need to use a waterbath. Another modern feature is the ability to link the Abbe refractometer to a computer to control the instrument and to record readings. Some Abbe refractometers can measure at wavelengths other than the standard 589 nanometers, using filters on up to the near infrared range. They are referred to as Multi-wavelength Abbe refractometers. Multi-wavelength Abbe refractometers can be used to easily determine a sample's Abbe number, which is a measure of the material's dispersion (variation of refractive index with wavelength) in relation to the refractive index. These multi-wavelength Abbe refractometers can be used to test eyeglass lenses, contact lens materials, optical plastics for optical communication, compact disk materials and insulating oil. Other accessories that are available include digital printers, extra filters and near-IR viewers.

Author Name: Kathy Brasch : Nationalmicroscope.com

Abbe Refractometers

Brix refractometers

You often hear the term brix and brix refractometer when testing samples for sugar content. Just what is a refractometer? A refractometer is an instrument that measures the refraction of light through a substance. The refractive index becomes higher in a substance of higher concentration.

A refractometer has a wide variety of uses such as measuring sugar concentrations and liquid concentrations. Refractometers are sometimes called “Sugar concentration meters” or “Density meters” depending on the application.
Brix and refractive index are common measurement scales for refractometers. A refractometer that measures brix is referred to as a Brix Refractometer. When measuring solutions that have multiple ingredients the Brix value equals the total concentration of dissolved solids.
About the Brix (%) Scale

Brix (%) shows the concentration percentage of the soluble solids content in a sample (water solution). The soluble solids content is the total of all the solids dissolved in the water, including sugar, salts, protein, acids, etc., and the measurement reading is the sum total of these. Basically, Brix (%) is the number of grams of cane sugar contained in 100g of cane sugar solution. When measuring a sugar solution, Brix (%) should perfectly match the actual concentration. With solutions containing other components, especially when one wants to know the exact concentration, a conversion chart is necessary.

Digital versus Analog Brix refractometers

Brix refractometers are available in hand-held (analogue) or digital models. Hand held units are read by putting a drop of sample on the prism, closing the daylight plate and then reading the scale through an eyepiece as the instrument is held up to your eye. A hand-held/analogue unit determines the refractive index or brix by use of the “Transparent System” which measures light as it passes through the sample and the prism. A low concentration sample has a larger angle of refraction so the boundary line falls on the lower part of the scale, whereas a high concentration sample has a small angle of refraction so the boundary line appears in the upper part of the scale.

Digital Brix refractometers use the “Reflected light system. When you put a sample on the prism and press the Start button, the light that is transmitted from under the sample will travel and refract in multiple directions. The angle of reflection is proportional to the refractive index of the sample, and the reflected light is measured by a sensor and converted into the refractive index or brix readout.

Because of their versatility, brix refractometers are used widely to test sugar content in fruit, vegetables, wine and other food products.

Author Name: Kathy Brasch : Nationalmicroscope.com

Brix refractometers

How a Polarimeter works: A more detailed explanation

Light waves as it travels. As shown in Figure 1, light may seem to travel unidirectionally. In actuality light travels in all directions as shown in Figure 2.


When light, which waves in all directions, goes through a grating placed in its course of travel, only the light wave that oscillates in the direction parallel to the bars of the grating passes through, Light waves that oscillate in other directions get blocked by the bars of the grating. ( Figure 3 ) Such light, which waves in one particular direction, is called polarized light, and the grating is called a polarizing plate.

When polarized light travels through in a polarimeter an observation tube filled with a sample solution that does not make light rotate (water, for example), the light continues to wave in the same direction even after passing through the solution. ( Figure 4 )


In contrast, when it travels through in a polarimeter an observation tube filled with a sample solution that makes light rotate (sucrose solution, for example), the light wave begins to rotate as it passes through the solution. (Figure 5) This is called optical rotation.


Those samples that make light rotate have a molecular formula that contains asymmetric carbon ( indicated by "C" ) . Sugar is the most common. The explanation of the asymmetric carbon can be highly technical. Imagine making a light path by placing a polarizing plate, an observation tube, another polarizing plate, and a sensor one after another. (Figure 6 and 7). The path in Figure 6 has an observation tube filled with water, in Figure 7 a sample solution, such as sucrose solution, that makes light rotate, such as you would find in a polarimeter.



In Figure 6 a certain amount of light reaches the sensor.

In Figure 7 the light does not reach the sensor. (Technically speaking, in terms of a vector an imperceptible amount of light does reach the sensor, but let's assume that the light does not reach the sensor here. )

When the second polarizing plate is rotated as shown in Figure 8, the same amount of light as in Figure 6 now reaches the sensor.


Conducting Zero-Setting on a Polarimeter
Conduct zero-setting in the step shown in Figure 6. In the actual adjustment procedure, the observation tube filled with water is not necessary and zero-setting is conducted by letting light travel through the air. Next, place an observation tube filled with a sample solution that makes light rotate as shown in Figure 8. Rotate the second polarizing plate so that the equal amount of light reaches the sensor as it did when zero-setting was conducted. The measured angle of the rotated polarizing plate is the angle of rotation of the sample solution.

Author Name: Kathy Brasch : Nationalmicroscope.com

How a Polarimeter works: A more detailed explanation

How A Polarimeter Works: The Simple Explanation

Imagine tying a piece of thick rope to a hook in a wall, and then shaking the rope vigorously. The rope will be vibrating in all possible directions - up-and-down, side-to-side, and all the directions in-between - giving it a really complex overall motion. Now, suppose you passed the rope through a vertical rectangular hole, like this: []. The rope has a really tight fit in the hole. The only vibrations still happening at the other side of the hole will be vertical ones. All the others will have been prevented by the hole.

What emerges from the hole could be described as "plane polarized rope", because the vibrations are only in a single (vertical) plane. Now look at the possibility of putting a second hole on the rope. If it is aligned the same way as the first one, the vibrations will still get through. But if the second hole is at 90° to the first one (so horizontally), the rope will stop vibrating entirely to the right of the second hole. The second hole will only let through horizontal vibrations - and there aren't any.

Light is also made up of vibrations - this time, electromagnetic ones. Some materials have the ability to screen out all the vibrations apart from those in one plane and so produce plane polarized light. The most familiar example of this is the material that Polaroid sunglasses are made of. If you wear one pair of Polaroid sunglasses and hold another pair up in front of them so that the glasses are held vertically rather than horizontally, you'll find that no light gets through - you will just see darkness. This is equivalent to the two holes at right angles in the rope analogy. The polaroids are "crossed". (This not exactly the way Polaroid glasses work, but it gives a good idea).

A polarimeter works the same way: You have two polaroid glasses, like the two holes with the rope, one glass is the polarizer, the other glass is the analyzer. The polarizer ensures that only a beam of polarized monochromatic light (light of only a single frequency - in other words a single color) is passed through the solution behind the polarizer in the polarimeter. After the tube with the solution is the analyzer. The polarimeter is originally set up with water in the tube. Water isn't optically active - it has no effect on the plane of polarization. The analyzer is rotated until you can't see any light coming through the polarimeter. The polaroids are then "crossed".

An optically active substance is a substance which can rotate the plane of polarization of plane polarized light. If you shine the polarized monochromatic light through a solution with an optically active substance, then light emerges: its plane of polarization is found to have rotated. The substance rotates the plane of polarization of the light, and so the analyzer won't be at right-angles to it any longer and some light will get through. You would have to rotate the analyzer in order to cut the light off again.

The rotation may be either clockwise or anti-clockwise. Assuming the original plane of polarization was vertical, you can easily tell whether the plane of polarization has been rotated clockwise or anti-clockwise, and by how much.


Author Name: Kathy Brasch : Nationalmicroscope.com

How A Polarimeter Works: The Simple Explanation

Principals of Refractometers

Water is placed in a reservoir. When a pencil is dipped into the water, the tip appears bent. Now put concentrated sugar water into a cup and try the same thing. The tip of the pencil should appear even more bent. This is the phenomenon of light refraction. Refractometers are measuring instruments in which this phenomenon of light refraction is put to practical use. They are based on the principal that as the density of a substance (e.g. when sugar is dissolved in water), it's refractive index rises proportionately.

When a straw is placed into a glass of water, the straw appears bent. Now if a straw is placed in a glass with water containing dissolved sugar, the straw should appear even more bent (see illustrations). This phenomenon is known as the principle of light refraction. Refractometers are measuring instruments which put this phenomenon of light refraction to practical use. They are based on the principle that as the density of a substance increases (e.g. when sugar is dissolved in water), its refractive index (how much the straw appears bent) rises proportionately. Refractometers were devised by Dr. Ernst Abbe, a German/Austrian scientist in the early 20th century.

The prism in refractometers has a greater refractive index than the sample solution. Measurements are read at the point where the prism and solution meet. With a low concentration solution, the refractive index of the prism is much greater than that of the sample, causing a large refraction angle and a low reading. The reverse (lower refraction angle and higher reading) would happen with a highly concentrated solution.
There are two detection systems for refractive index: transparent systems and reflection systems. Hand-held refractometers and Abbe refractometers use transparent systems, while digital refractometers use reflection systems.

Transparent Systems
The detection system for hand-held refractometers (transparent system) is summarized below.
1. In the figure below the detection is done by utilizing the refractive phenomenon produced on the boundary of the prism and sample. The refractive index of the prism is much larger than that of the sample
2. If the sample is thin, the angle of refraction is large (see "a") because of the large difference in refractive index between the prism and the sample.
3. If the sample is thick, the angle of refraction is small (see "b") because of the small difference in refractive index between the prism and the sample.

Reflection Systems

In the figure below, Light A, being incident from the lower left of the prism, is not reflected back by the boundary, but exits through the sample. Light B is reflected by the boundary face to the right, directly along the prism boundary. Light C, having an incident angle too large to be let through to the sample side, is totally reflected toward the lower right of the prism.

As a result, a boundary line is produced dividing light and dark fields on either side of the dotted line "B' " in the figure. Since the angle of reflection of this boundary line is proportional to refractive index, the position of the boundary line between light and dark fields is caught by a sensor and converted into refractive index.

Author Name: Kathy Brasch : Nationalmicroscope.com

Principals of Refractometers

Choosing A Microscope: Compound or Stereo microscope?

Your application is the most important factor in choosing a microscope. What you need to see and what you want to do with that image will determine what kind of microscope you need. Microscopes typically come in two types: compound or stereo microscope.

The most common is the compound microscope. It is the one most people visualize when they think about microscopes. A microscope with one eyepiece is called a monocular microscope; with two eyepieces it is called a binocular microscope, or it might have an additional camera tube and is called a trinocular microscope. The compound microscope has a number of objectives (the lens closest to the object being viewed) of varying magnification mounted in a rotatable nosepiece. It uses a light source beneath the stage to illuminate slides. These microscopes are generally used to view very small objects such as cells or bacterium. Magnification of compound microscope scopes range from 40X up to 1000X. Actual magnification can be figured by multiplying the power of the eyepiece by the power of the objective lens.

The other type of microscope is called a stereo microscope or dissecting microscope. It uses two eyepieces and two paired objectives. Stereo microscopes come in models that have full zooming capability and models that just have only two magnification settings. Stereo microscopes are particularly useful for biologists performing dissections, technicians building or repairing circuit boards, paleontologists cleaning and examining fossils or any one who needs to work with their hands on small objects. You can find stereo microscopes that have a built in light source from above, below, or none at all. Magnification is usually much less than that of a compound microscope, but is figured in the same way by multiplying the power of the eyepiece by the power of the objective lens.

Author Name: Kathy Brasch : Nationalmicroscope.com

Choosing A Microscope: Compound or Stereo microscope?

Digital Microscope

A digital microscope is real 21st century advancement on microscope technology. It comes with software for your computer that allows you to see real-time images on your monitor of what you're observing with the microscope. Take a step into the modern age by learning how to use a digital microscope.

With the advent of computers and the digital era things have improved a lot. You can now buy a handheld digital microscope from the market at affordable prices which will plug straight into the USB port of almost any computer, and displays and records the image in real-time. A digital microscope still uses optics much the same way as a traditional microscope, but also has a built-in digital camera, which works just like a webcam but with magnification. The software that comes with these cameras will let you take still or video pictures while magnifying the image by 200 times or more. You can then use your regular image software to manipulate and use the picture in many ways.

Although these digital microscopes are obviously great in a science classroom environment where a teacher can present and discuss a rapid sequence of images, don't neglect their home use. Digital microscopes offer an amazing insight into the world around us from a rarely seen perspective.

Digital microscopes were brought to a new level of excellence with the introduction of Olympus' MIC-D. The MIC-D uses a USB connection to the computer for live, full-color images to be displayed on a monitor screen. The design of the MIC-D is inverted, which means that the lens is tilted up at the stage instead of positioned down at the specimen. This feature allows large objects and dishes of water to be magnified with amazing clarity. A further innovation of the MIC-D's design is that it uses one master lens instead of a series of fixed lenses.

Author Name: Kathy Brasch : Nationalmicroscope.com

Digital Microscope

Stereo Microscope

A stereo microscope is used for comparing two side-by-side specimens. It consists of two regular microscopes connected together with an optical bridge. They are commonly used in fields such as forensics, where fingerprints, DNA or a sample must be compared in great detail to another. A stereo microscope provides the viewer with an upright and laterally correct image as opposed to the upside-down and backwards image that a compound microscope provides. The stereo microscope also has a greater distance in most cases between the stage and the objective, so that the specimen can be worked on or dissected while it is being viewed.

The stereo microscope, by virtue of its twin eyepieces, allows you to view your specimen with both eyes and get a much more accurate view of its surface. The human visual system only perceives depth accurately when both eyes are viewing an object, so using a compound microscope with one squinting eye can produce a distorted idea of what is actually being seen.

The stereo microscope also has two magnification systems: fixed and zoom. Fixed magnification is achieved using a pair of objective lenses with a set magnification degree. Basically, the degree of magnification that you get solely depends on what your lenses are capable of.

Stereo microscopes are also capable of digital displays, as in the case of digital microscopes. Having the image projected on a high resolution monitor is very useful especially in surgeries. Microscopes have truly gone a long way. Previously, only one lens is used; today, microscopes with two optical paths are in existence.

Zoom magnification, on the other hand, allows the user to use varying degrees of magnification. Have you ever heard of the terms "zoom in" and "zoom out?" Stereoscopes with zoom magnification are capable of handling slide-prepared specimens. The versatility of a stereo zoom microscope means that you’ll never be without a way to study whatever catches your eye.

Author Name: Kathy Brasch : Nationalmicroscope.com

Stereo Microscope

Microscope Camera

The digital microscope camera is an amazing thing of modern science. A digital microscope consists of a regular microscope with a digital camera built into it. The images seen through a digital microscope can be projected to a computer monitor and saved on a computer file. A digital microscope is perfect for education because it lets many people view the specimen at once. The data saving capabilities of a digital microscope make it a great tool for research.

A wide range of microscope cameras are available in the market like cmos digital camera, ccd digital cameras, slr camera and video cameras online. These microscope cameras are useful for many purposes. Meiji and VanGuard are two of the big brands for microscope cameras. When a microscope camera is added on digital microscope, extensibility and uses of the microscope increase. This device is ideal for anyone using a microscope. Most digital microscopes connect to computers via a USB port. Once the microscope is connected to the computer, the images seen through the microscope’s eyepiece can be shown on the computer’s monitor and saved on the hard drive for future use. Images can be printed if the computer is equipped with a digital printer.

A wide range of microscope camera accessories are available in the market to increase its capabilities. A microscope camera is very useful for education, research, medical and many other science applications. A microscope camera is connected to the eyepiece of the microscope. The digital camera can be used in a wide variety of ways, and adds a higher degree of function to your microscope.

Author Name: Kathy Brasch : Nationalmicroscope.com

Microscope Camera

Trinocular Microscope

A Trinocular microscope is virtually the same as a binocular microscope but adds a third eyepiece tube. Trinocular microscope models have two eyepieces for normal viewing, plus a third "phototube" on which you can mount a camera without interfering with the normal operation of the microscope. No, it's not for people with 3 eyes, but for people who wish to attach a camera to the third eyepiece and be able to photograph or video what they can see through the two eyepieces. You should consider purchasing a trinocular microscope if photography is needed option.

There are many different methods for capturing, displaying, and recording microscope images, and each has its own advantages and disadvantages. It would be impossible to cover all of these options here but access to these options is important in selecting your microscope. It is possible, but not practical to mount a camera on a monocular or binocular microscope.

A trinocular microscope may be an optical, acoustic, or an electron microscope. In other words, it may be a microscope in which the specimen is illuminated by visible light, by sound, or by a particle beam of electrons. The third eyepiece can also be added to a stereo microscope. A binocular compound microscope uses one lens array for the objective but has a pair of eyepieces, with the light from the image formed by the objective split by a prism.

A trinocular microscope has one of several purposes. One purpose is to allow a second viewer access to a specimen at the same time as the person who is mainly using the microscope. Another purpose of a trinocular microscope is to allow the use of technology to either preserve the images seen through the microscope by recording them or projecting them.

We start with the premise that choosing a microscope should be an enjoyable process! There are a number of variables that go into selecting any kind of microscope system like a trinocular microscope, monocular or binocular microscope. The process can be a little daunting. Moreover, there is a bewildering range of quality - from cheap plastic microscopes to the most expensive German and Japanese brands.

Microscopes are configured to suit different applications. It is important to ensure that you purchase a microscope that is well-suited to your application.

Author Name: Kathy Brasch : Nationalmicroscope.com

Trinocular Microscope

Microscopes - Polarizing Microscopes

A polarizing microscope is a scientific instrument used to make optical measurements. Polarizing microscope is a special kind of microscope that utilizes two polarizing lens to acquire data from the specimen. The polarizing microscope is used extensively in the field of optical mineralogy which supports such applications as geology, asbestos testing, and forensic science. Often those working in different fields will sometimes refer to the polarizing microscope by different names such as geology microscope, petrographic microscope and pol microscope.

Polarizing microscopes can be used to measure various optical properties of a material, including linear birefringence, circular birefringence, linear dichroism, circular dichroism and scattering. To measure these various properties, there have been many designs of polarimeters. Some are archaic and some are in current use.

The key difference between the polarizing microscope and a standard compound microscope is the addition of a fixed polarizer between the light source and the specimen and the addition of an adjustable polarizer between the objective and the eyepieces. The second polarizer is called the "analyzer" and usually can be inserted in and out on a rotating piece in the neck of the microscope. Other common accessories include a rotating stage and insert able retardation plates made from gypsum or quartz.

The first use of these kinds of microscopes over one hundred years ago was for the identification of minerals in geology. In addition, the most common form of lab analysis to test for asbestos is performed with a polarizing microscope. Because of their ability to provide optical data, these kinds of microscopes are very commonly used in forensic science where the identification of unknown materials is a routine part of the job.

The polarizing microscope is a very versatile and powerful instrument in the identification of materials and provides the very accurate results. It is a key tool in several scientific fields, and can sometimes be the best option over more expensive technologies. The polarizing microscope is a very cost effective instrument for research and analysis industry and you can buy it online through our webstie e-store.

Author Name: Kathy Brasch : Nationalmicroscope.com

Microscopes - Polarizing Microscopes