Microscopes are instruments used to observe the details of minute objects, such as cells and microorganisms. They produce an enlarged image of the object that is otherwise invisible to the naked eye. Different parts of the microscope work in coordination to produce the image of the object under examination. There are different types of microscopes depending on their magnification ranges. The most basic and best type of microscope is the compound light microscope, other advanced types include stereo microscopes, electron microscopes, and digital microscopes.
With any instrument comes errors, the same is the case with microscopes. Any error or uncertainty in the measurement of the microscope can affect your results. For this reason, we have to calibrate the microscope. In this article, you will discover everything about calibration, its importance, and how to calibrate microscopes.
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What is Meant by Calibration?
Calibration is done on the instruments to maintain their accuracy. It means configuring an instrument so it gives results within the acceptable or standard range. Calibration is done to remove any factors that lead to errors or inaccurate measurements. The process of calibration is different for each instrument. However, it involves the testing of measurement of different samples called the ‘’calibrators.’’ The results obtained from different calibrators are compared with others having known values or having values within the specified range.
How to Calibrate the Microscope?
To calibrate a microscope, you need a stage micrometer and an eyepiece graticule. Let’s say, for example, we will consider that the divisions on the eyepiece graticule are known as ‘’ocular units.’’ If we observe the cell with a 10x objective lens, then it may measure as 2 ocular units (ou). When it is switched to 40x, it will measure 8ou. How many micrometers will this be equal to? To find out, follow these few steps to calibrate your microscope:
Setting Up of Stage Micrometer and Graticule
The first step of calibrating a microscope is to set up the stage micrometer in such a way that it lies at the center under the objective lens. Set the eyepiece graticule by loading it in the eyepiece.
Aligning the Stage Micrometer and Eyepiece Graticule
The next step is to align the stage micrometer and eyepiece graticule. Start this process with a 10x objective lens. Line up the divisions of both stage micrometer and graticule. The first major bar on the left of the eyepiece graticule should line up with the first bar on the left of the stage micrometer. It is denoted as 0 µm. Try to line up as many divisions as possible.
Calculating the Value of Ocular Units
Say, for example, the stage micrometer has a length of 1000 µm. Each major division is 100 µm as the length is divided by 10. For example, if the eyepiece graticule lines with 6.9 on the stage micrometer, then the length of the eyepiece graticule will be 690 µm. When we divide both sides by 10, then it means 1 ou = 69 µm.
Repeating the Process for Other Objective Lens
As we have calculated the ocular units with an objective of 10x magnification, now you can repeat the same process after switching them with other objective lenses having variating magnification powers.
Why Calibration is Important?
Calibration is important for any measuring instrument. It ensures accurate measurements leading to quality results. Errors of any kind can affect the overall results, So, for this reason, calibration is important to produce results within the specified range. Over time, the performance of instruments can be affected, and as a result, measurements are also affected. Calibration assures precise measurements and makes the instrument free of any uncertainties. There is no place or field where instruments are not used, and calibration is not required.
The calibration of the microscope is important to assess whether the same samples yield the same results when examined with different microscopes. If the microscopes are not calibrated, then the results can vary slightly even when you use the two identical microscopes. There are no standard units of measure on the scale of the eyepiece graticule. Thus, to get a true measurement of the scale markings, calibration of the microscope graticule is important.
Following is the list of examples of places or fields where calibration is used.
- Transportation system including cars, trains, buses, etc.
- Electronics including, phones, computers, home appliances, etc.
- Pharmaceutical products and medications
- Medical devices such as pacemakers, BP apparatus, etc.
- Aerospace systems including, rockets, satellites, etc.
- Food industry
- Trade industry
- Scientific research and development
Bottom Line
Microscopes are used to see minute objects. It produces an enlarged image of the object under examination. Microscopes are used to measure the details of minute objects; thus, it is a measuring instrument, and all measuring instruments need to be calibrated. Calibration ensures the accuracy of the measurements produced by the instrument. Calibration is done to maintain the quality of results produced each time by the instrument. It makes your results free of uncertainties. Microscopes are calibrated by using a stage micrometer and eyepiece graticule. Different magnification powers of the objective lens can be used to calibrate the microscope.
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