A Multi-range Voltmeter

Radio Record, Volume V, Issue 26, 8 January 1932, Page 13

A Multi-range Voltmeter

LOW-READING voltmeter can easily be adapted to read voltages outside its range by placing a compression type high yesistance in series with it. First of all, however, measure the voltage of a grid bias batterysay, one of nine volts. Now include the resistance in the circuit and so adjust it that the meter reads 45 volts. The actual voltage is, of course, 9 volts, and so we must multiply the reading by two. Next take a "B" battery of the type having numerous taps. Place the voltmeter and resistance across 18 volts, when the reading will be, say, 9. Now increase the resistancg till the reading is 4.5. As the actual voltage is 18, the scale readings must now be multiplied by 4. Proceed aldng these lines until the desired voltage.range is obtained.