We don't need to know the actual distance between marks on it. When the zero marks are lined up, scan across and look for a convenient point where the lines converge again.
If you look at the 30 mark on the reticle, you will see pretty close alignment with the stage micrometer. How many divisions? Did you say 20? You are right! And, if each line is 10um wide, what will 20 lines equal? Answer: um. Now it is just a simple math ratio. So what does one division on the reticle equal? Let's see, 30 is to as one is to X. Remember how to do a ratio?
Two fractions, 30 over equals 1 over X. If you change objectives, you need to recalculate. The knob magnifications, or click stops, are found on the knob here, and I have listed them below.
When you multiply these number across, you find the true magnification for the microscope. Now I will give a brief overview for the five steps for calibrating your objectives.
We will go into greater detail for these steps in the following slides. First, you will want to calculate the distance of each stage micrometer division. Observe the unit of measure of the certified stage micrometer from the units on the micrometer itself or on the Certificate of Analysis. Sometimes, the stage micrometer will have the distance between each division noted right on it. Here, I have an image of what a typical micrometer scale will look like.
We can run through the example using the formula above. Moving on to the second step in calibrating your objectives. Line up the micrometer with your eyepiece reticle scale. Place the stage micrometer on the stage of the microscope and bring the scale into focus.
Onto the third step of calibrating your objectives. Count divisions and calculate size of a single division for that magnification. Count the number of stage micrometer divisions that match up with the largest visible number of the eyepiece reticle divisions and enter in the following equation:. For this example, I took an image of the scale bars at click stop 6, magnification 90X. On to the fourth step of calibrating your objectives. Increase magnification and repeat calculations for each click stop.
Every time you increase magnification, you will need to realign the zeros from both scales and count the divisions. Continue this process until you have calculated the size of one division at each magnification. Here I have some examples of what the different click stops and magnifications would look like.
On to the fifth, and final, step of calibrating your objectives: create a sizing chart for your work station. Instead of making calculations every time you measure a particle, create a cheat sheet to expedite your observation process.
Now grab your click stop and magnification numbers from the previous calculations, and start to fill them into a chart in Excel this will be the header. The first row following the header will be the length on one eyepiece reticle division at that click stop. You can easily expand your chart by using simple multiplication.
This chart comes in handy, say, for example, if you were working at click stop 3, you can grab your chart and see that you are working at 45X.
The scale on the stage micrometer is aligned with the grid on the reticle and a reading is taken. When objects are magnified, the image size increases but the reticle units remain unchanged. Microscope reticle calibration will determine the conversion for each power level of the objective lens. Request a Quote Contact Us. I have inspected the samples provided and am impressed with the quality of work. I look forward to working with LTI in the future. Copyright Laboratory Testing Inc. All rights reserved.
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