The caliper is and instrument of measurement dopted of one scale and a cursor that slides on it. It was developed to take external linear measures by contact. Also can measure internal dimensions, depths, rebounds and others. Possibly, this is the most common instrument of metrology and its architecture was modified to take special measures.
The main scale of this simulator is graduated in inch - english system or imperial of british measures - that is divided in tenths, that is subdivided by four. The vernier divides the 0.025in (twenty and five thousandth of inch) by twenty and five, marking the 0.001in (one thousandth of inch).
To comprehend the sciense of measurement in fractional inch, read and interact with the pages:
Vernier scale - Simulator of reading and interpretation of thosuandth inch resolution 0.001" and
Conversion of millimeter and fractional and thousandth inch - interactive conversor - Metrology