Write about methods of measurement of $pH$ of a solution.

The measurement of $pH$ of a solution is essential in various fields,including biological and cosmetic applications.
$1$. Rough Estimation using $pH$ Paper: The $pH$ of a solution can be estimated roughly using $pH$ paper,which exhibits different colors in solutions of different $pH$ values. As shown in the reference image,the $pH$ in the range of $0-14$ can be determined with an accuracy of $\sim 0.5$ using $pH$ paper.
$2$. Accurate Measurement using $pH$ Meter: For greater accuracy,$pH$ meters are used. $A$ $pH$ meter is a device that measures the $pH$-dependent electrical potential of the test solution with a precision of up to $0.001$. $pH$ meters as small as a writing pen are now commonly available.