The sliding part of the vernier calipers may be moved either by dragging the slider with the mouse or by clicking the left and right buttons.
Try taking the reading from the calipers. Type your value (with units) into the white box and press Enter or click on the Check Reading button. A message will appear on the line below. It will be one of the following:
If you have difficulty getting a correct reading click on the Help button. An explanation of how you should take the reading will appear below the calipers. Note that some of the lines on the calipers will be highlighted in colour so that they can be refered to in the explanation.
Try typing the value given by Help into the white box and press Enter. You should now be told that the value is correct.
Click on Help again to hide the explanation, move the slider and try again.
Once you are happy with entering measurements you can try measuring some objects. Click on the New Object button. A ball bearing will appear. Move the slider until it touches the ball bearing. Take a reading and check it. You will get a message as before. If you take the reading correctly without first making sure that the slider is touching the object to be measured you will be told that the slider is not touching the object. Click the left button repeatedly until the slider does not move any further then take the reading again. Once you have taken the reading correctly another object will appear for you to measure.
Why use vernier scales?
How Vernier scales work.