Choose a pot that has the greatest possible sensitivity and meets the non linearity requirements of 2 percent (max) from available pots having a thermal rating of 5 watts and resistance ranging from 200 ohm to 5000 ohm in steps of 50 ohm. The output of the pot is to be measured with a device of 4000 ohm input resistance. Determine maximum excitation voltage that can be employed with this pot?

Power rating of pot (P) = 5 watts Load resistance (Rl) = input resistance of measuring device = 4000 ohm Non – linearity to be limited = 2% Maximum possible % non – linearity = 15 (Rt/Rl)² = 15 (Rt/Rl) Total resistance of the pot = (Rt) = 2/15 Rl = 2/15 x 4000 = 533.3 ohm The pot having maximum value of total resistance, Rt will give greatest sensitivity and that possible resistance with a pot out of the available pots, which will also meet the requirements of 2% (max) non-linearity is 500 ohm Max excitation voltage that can be used with the above pot, (Vimax)² = PRt = 5 x 500 = 50 V