How do you make an improvised voltmeter?

Answer 1

You need to build a galvanometer first; this is a sensitive current meter. Simple designs involve wrapping loops of wire around a compass. Then select a relatively high resistance and make a series circuit in this order:

1) voltage source

2) resistor

3) galvanometer

The small current flowing through the circuit (due to the high resistance) will be noticeable in the deflection of the compass needle. The resistor should be chosen to limit the current in the circuit so that the deflection is noticeably different for different applied voltages. If the resistance is too small, all voltages will cause a full deflection of the compass needle. If the resistance is too large, there will not be any noticeable deflection for your choice of voltages. Higher voltages should cause greater deflections.

http://madlabs.info/galvanometer.shtml

hope that helps,

M

Answer 2

You might use a glass tube with water. That will work for temperatures above about 5 or 10 degrees centigrade.