Question

how can you make the spherometer more sensitive

Answer 1

If you are living in the northern hemisphere then in order to make the spherometer more sensitive you are required to use an electromagnet installed with a  variable resister that will help in balancing out the intrinsic counter clockwise torque.

If you are living in the southern hemisphere then one is just required to reverse the polarity of the electromagnet.

Answer 2

$\huge \mathfrak{spherometer}$