Why calibrated ocular micrometer

Beside above, how do you calibrate an ocular micrometer? To achieve the calibrated measurement of the sample, multiply the measured value of the sample by the labeled magnification of the objective lens divided by the actual magnification ratio.

An ocular micrometer is a glass disk with ruled scale on the surface which is etched in chromium. The magnification is different for each objective lens. The numerical aperture value holds only for the specific objective ocular lens combination. Ocular space changes with each objective change. The stage micrometer is used to calibrate an eyepiece reticle when making measurements with a microscope.

Eyepiece Reticle or reticule -a small piece of glass with a ruler etched into it that fits into a microscope eyepiece. This ruler is used to make measurements of objects viewed through the microscope. The ocular micrometer should be calibrated for each objective lens and recorded. This is necessary only once for each magnification and each microscope.

After such calibrations, microbial size can be measured directly from the ocular micrometer. What do you mean by calibration? In information technology and other fields, calibration is the setting or correcting of a measuring device or base level, usually by adjusting it to match or conform to a dependably known and unvarying measure.

For example, the brightness or black level of a video display can be calibrated using a PLUGE pattern. What is the calibration factor? Before a calorimeter is of any use to us we must first calibrate it. Calibration of the calorimeter is the determination of how many joules of energy are required to raise the temperature of the contents by one degree Celsius.

This is known as the calibration factor of the calorimeter. This is a standardized glass slide with an accurately ruled scale. A typical stage micrometer is depicted in Fig. The method for calibration follows: Protocol:. Place the stage micrometer on the microscope stage and focus on the marks with low power.

Superimpose the ocular micrometer on the stage micrometer so that the left edge of the ocular micrometer "O" lines up with the left edge of the stage micrometer. Visually scan the two micrometers to locate a place where a line from each micrometer is perfectly superimposed. Using the scale provided with the stage micrometer, determine the distance from the left edge of the ocular micrometer "O" to the superimposed lines.

Divide this distance by the total number of ocular micrometer units represented by this distance to yield the calibration factor mm omu Objectives with the same magnification can vary by a few percent from the same manufacturer. When you look through the eyepiece the markings remain constant but the size of the specimen magnified will increase along with the magnification.

Thus, switching to a higher power objective lens, the represented value between marks will change proportionately. For example, if each mark represents 0. As an example, for a reticle that is 10mm long with divisions as shown above , each division was found to represent the following distances:. The correct way to calibrate a reticle with a stage micrometer is to line up the left edges of each.

For instance if 22 lines from left to right on the reticle line up with 55 micrometers actual measurement on the stage micrometer. Then 22 markings is to 55um as one line is to X micrometers. The calculation and "X" can be solved by dividing 55 by Each line on the reticle then equals 2.