Vernier caliper: It is a measuring instrument used to measure the inner diameter - between the upper jaws-, the outer diameter - between the lower jaws-, and the measurement of depth from the tip extending from the end of the vernier.
Note: when the upper jaw moves, the lower jaw moves and the tip of the depth gauge is also moving.
Good article on How To Read A Vernier Caliper
This question may be useful: How to draw a Micrometer scale using TikZ
The purpose of drawing: it is to give examples for students to practice reading.
Minimal example:
\documentclass{book}
\usepackage{tikz}
\usepackage{pdflscape}
\usepackage[bottom=0.1cm,top=0cm,]{geometry}
\begin{document}
\begin{landscape}
\tikzset{every picture/.style={line width=0.75pt}} %set default line width to 0.75pt
\begin{tikzpicture}[x=0.75pt,y=0.75pt,yscale=-1,xscale=1]
%uncomment if require: \path (0,300); %set diagram left start at 0, and has height of 300
%Straight Lines [id:da05798354966158592]
\draw (109,144) -- (108,253) ;
%Curve Lines [id:da20888122911675122]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (54,144) .. controls (52,137) and (74,254) .. (109,252) ;
%Straight Lines [id:da024053498740669088]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (54,54) -- (54,144) ;
%Straight Lines [id:da6430118790832982]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (54,54) -- (72,54.5) ;
%Straight Lines [id:da08715483033237725]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (109,144) -- (900,144) ;
%Straight Lines [id:da46733400478979537]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (900,144) -- (900,72) ;
%Straight Lines [id:da857349721059119]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (72,54.5) -- (72,35) ;
%Curve Lines [id:da9047870987415094]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (72,35) .. controls (94,51) and (90,71) .. (90,71) ;
%Straight Lines [id:da7189113520178745]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (54,71) -- (900,72) ;
%Straight Lines [id:da5946578716718982]
\draw [color={rgb, 255:red, 80; green, 227; blue, 194 } ,draw opacity=1 ][line width=1.5] (54,144) -- (109,144) ;
%Curve Lines [id:da03826128003758833]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (108,36) .. controls (88,46) and (90,97) .. (90,90) ;
%Straight Lines [id:da5429773860531661]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (108,36) -- (108,55) ;
%Straight Lines [id:da5757330738280348]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (108,55) -- (234,55) ;
%Straight Lines [id:da998619902773833]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (234,55) -- (234,90) ;
%Straight Lines [id:da7858832655058519]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (90,90) -- (234,90) ;
%Straight Lines [id:da3951728658697151]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (109.5,126) -- (108,252) ;
%Curve Lines [id:da9512506883935523]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (108,252) .. controls (153.5,234) and (158,183) .. (163,163) ;
%Straight Lines [id:da05030603441939685]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (109.5,126) -- (289.5,127) ;
%Straight Lines [id:da969257477330393]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (289.5,127) -- (289,163) ;
%Straight Lines [id:da8211999121045548]
\draw [color={rgb, 255:red, 126; green, 211; blue, 33 } ,draw opacity=1 ][line width=1.5] (163,163) -- (289,163) ;
%Shape: Rectangle [id:dp36441455697148095]
\draw [color={rgb, 255:red, 0; green, 0; blue, 0 } ,draw opacity=1 ][fill={rgb, 255:red, 201; green, 196; blue, 196 } ,fill opacity=1 ] (127,90) -- (900,90) -- (900,108.5) -- (127,108.5) -- cycle ;
\end{tikzpicture}
\end{landscape}
\end{document}
