Measurement Resistance Quiz

Study Notes

Messwiderstand

Messwiderstand, or measurement resistance, refers to the electrical resistance encountered when measuring electrical quantities.
It's often a parasitic effect, meaning it's not a desired component of the circuit being measured.
High measurement resistance can distort the measurement process, introducing errors.
Sources of measurement resistance can include:
- The resistance of the measuring instruments themselves (e.g., ammeters, voltmeters).
- The resistance of connecting wires.
- The resistance of the probes or contacts used to connect to the circuit.
- Internal resistance of the device under test.

Factors Affecting Messwiderstand

Instrument sensitivity: More sensitive instruments generally have lower internal resistance, minimizing measurement errors.
Circuit configuration: The arrangement of components in the circuit can significantly affect the overall resistance encountered during measurement.
Wire gauge: Thinner wires have higher resistance, which can contribute to measurement errors, particularly in high-current applications.
Contact resistance: Poor connections or contacts between wires and components create additional resistance, affecting the overall measurement accuracy.
Temperature: Resistance changes with temperature, thus temperature variations can influence the accuracy of measurements.

Types of Messwiderstand

Input resistance: The resistance presented by the input terminals of a measuring instrument.
Output resistance: The resistance presented by the output terminals of a measuring instrument.
Contact resistance: Resistance between components in electrical contact.
Internal resistance: Resistance within a component under test, often overlooked in simplified circuit models but crucial for accurate readings.

Minimizing Messwiderstand

Using high-quality, low-resistance wires.
Utilizing measuring instruments with low internal resistance.
Proper contact pressure in connections (e.g. tightening connections securely).
Using appropriate meters for the current/voltage range being measured to avoid overloading the meter.
Utilizing shielded cables. Shielding reduces inductive and capacitive coupling, lessening interference.
Utilizing instruments with high input impedance or employing specialized techniques for measurements where high input impedance is crucial.
Compensating for known sources of error (e.g., using correction factors for temperature variations or contact resistance).

Impact on Measurements

Measurement resistance can lead to inaccurate readings. For example:
- Overestimation of small voltages. (Voltmeter affects circuit).
- Underestimation of high resistance values. (Inaccurate reading influenced by instruments' high impedance).
The magnitude of error depends on the magnitude of the measured parameter and the resistance value. A large measured voltage is less affected than a smaller one.
In high-impedance circuits, the resistance of the measuring instruments becomes critical to the overall measurements.
Using an ammeter to measure current introduces some series resistance which changes the current the circuit is trying to measure.

Calibration

Calibration procedures are crucial to ensure accuracy in measurements by controlling for the effect of measurement resistance.
Instruments require periodic calibration to confirm that their readings are accurate and reliable.
Calibration results often provide a correction factor to account for the instrument's measurement resistance. Correcting for the internal resistance ensures more accurate measurements.

Description

Test your knowledge on measurement resistance, a key concept in electrical measurements. This quiz covers sources of measurement resistance, factors affecting accuracy, and the importance of instrument sensitivity. Enhance your understanding of how measurement resistance impacts electrical circuits.