Lab 2: Practical Voltage and Current Measurement

Practical Voltage and Current Measurement

Joel Cook

March 1, 2018

Purpose: 

The purpose of this lab is to construct a circuit and take measurements to explore the behavior of non-ideal voltage measurements. Taking measurements of a circuit affects the circuits operation and this help will help determine to what extent.

Data:

Pre-lab:

We began by calculating the measured voltage, Vout, of the circuit with an ideal voltmeter that contributes no resistance to the circuit. As shown, the voltage measured would be 2.5V.

We calculated the equivalent resistance with the attached DMM in terms of Rm, the internal resistance of the meter.

Data:

We constructed the circuit as shown in the photo below. The resistors used are 10Mohm resistors.

We measured the voltage with the following tool and laptop:

We read 0.335 Volts as shown below.

We estimated the internal resistance of the analog device as shown:

We calculated the internal resistance to be 774000 ohms.

We repeated the measurements with the DMM and got a reading of 1.57 volts. We calculated the internal resistance of the DMM to be 8440000 ohms, as shown below.

Conclusion:

As seen in the results, the use of a non-ideal meter affects the reading of voltage in a circuit. We are not sure of the accuracy of the internal resistances that we measured but learned a great deal about calculating the internal resistance and understanding the impact it has on circuit measurements.