An investigator measures the resistance of a newly synthesized thin carbon-film sensor using two different diagnostic arrangements, as shown in the diagram below.
Method A: A simple handheld digital ohmmeter is connected directly across the terminals of the sensor.
Method B: A stable DC power supply, a high-precision digital milliammeter, and a high-precision digital voltmeter are configured to measure current and potential difference simultaneously.
Explain why Method B allows for a more precise determination of the resistance of the carbon-film sensor than Method A.