Vernier Caliper Simulation

# Vernier calipers

Vernier calipers can measure internal dimensions (using the uppermost jaws in the picture at right), external dimensions using the pictured lower jaws, and depending on the manufacturer, depth measurements by the use of a probe that is attached to the movable head and slides along the centre of the body. This probe is slender and can get into deep grooves that may prove difficult for other measuring tools.

The vernier scales can be in metric measurements on the upper and lower part of the scale.

Vernier calipers commonly used in industry provide a precision to a hundredth of a millimetre (10 micrometres).

A more precise instrument used for the same purpose is the micrometer

Parts of a vernier caliper:

1. Outside jaws: used to measure external diameter or width of an object (Blue)
2. Inside jaws: used to measure internal diameter of an object
3. Depth probe: used to measure depths of an object or a hole ( not shown in this model)
4. Main scale: gives measurements in mm.
5. Vernier gives measurements up to one decimal places in mm
6. Retainer: used to block movable part to allow the easy transferring a measurement ( not shown in this model)

The Vernier calipers model has

- an object (Blue) for the internal jaws to measure width of an object with slider to control width of the object and simple drag action to control position of object.
- an object (Green) for external jaws to measure internal diameter of a cylinder for example with slider to control dimensions of the cylinder.
- a slider for zero error slider
- checkbox for hint to scaffold the learners attention and point of focus
- checkbox for answer to show the meaning of reading on the main scale and the vernier scale with zero error calculations if any.
- drop down menu of the various common vernier scales for sense making and additional testing out by learners their ideas of how vernier works.
- fine <> control buttons for learners to manipulate the model with single incremental precision
- slider control for fast changes in the vernier measurement
- reset button to bring simulaton back to original (default) setting.

Credits:

The Vernier Calipers JavaScript Model was created by developed by Jiun Wei Chia based on a Java model by Fu-Kwun Hwang, Loo Kang Wee and Wolfgang Christian using the Easy Java/JavaScript Simulations (EjsS) version 4.2 authoring and modeling tool. A Java applet version of this model is available on the NTNU website < http://www.phy.ntnu.edu.tw/ntnujava/ >.

You can examine and modify this compiled EjsS source code available on the in the OSP comPADRE collection <http://www.compadre.org/OSP/>. You must, of course, have EJS installed on your computer. Information about EJS is available at: <http://www.um.es/fem/Ejs/>.