# Potentiometric Voltmeter

## Chapter 3 - DC Circuits

PARTS AND MATERIALS
• Two 6 volt batteries
• One potentiometer, single turn, 10 kΩ, linear taper (Radio Shack catalog # 271-1715)
• Two high-value resistors (at least 1 MΩ each)
• Sensitive voltage detector (from the previous experiment)
• Analog voltmeter (from the previous experiment)
The potentiometer value is not critical: anything from 1 kΩ to 100 kΩ is acceptable. If you have built the “precision potentiometer” described earlier in this chapter, it is recommended that you use it in this experiment. Likewise, the actual values of the resistors are not critical. In this particular experiment, the greater the value, the better the results. They need not be precisely equal value, either. If you have not yet built the sensitive voltage detector, it is recommended that you build one before proceeding with this experiment! It is a very useful, yet simple, a piece of test equipment that you should not be without. You can use a digital multimeter set to the “DC millivolt” (DC mV) range in lieu of a voltage detector, but the headphone-based voltage detector is more appropriate because it demonstrates how you can make precise voltage measurements without using expensive or advanced meter equipment. I recommend using your home-made multimeter for the same reason, although any voltmeter will suffice for this experiment. CROSS-REFERENCES Lessons In Electric Circuits, Volume 1, chapter 8: “DC Metering Circuits” LEARNING OBJECTIVES
Potentiometric voltmeter v1 1 0 dc 6 v2 3 0 r1 1 2 1meg r2 2 0 1meg rnull 2 3 10k rmeter 3 0 50k .dc v2 0 6 0.5 .print dc v(2,0) v(2,3) v(3,0) .end