What could cause a voltage drop measured across the contacts of a relay switch?

A voltage drop measured across the contacts of a relay switch can indeed be attributed to dirty or corroded contacts. When relay contacts are compromised by dirt, corrosion, or oxidation, their ability to conduct electricity efficiently is reduced. This increased resistance at the point of contact leads to a decrease in voltage that can be measured across the contacts.

Properly functioning contacts should allow for maximum voltage transfer, which enables the relay to operate correctly. However, as contaminants build up over time, they interfere with this process. Consequently, the increased resistance results in a measurable voltage drop when the relay attempts to conduct electrical current, highlighting the importance of routine maintenance and inspection to ensure the integrity of relay contacts.

While other considerations like improper connections, damaged wiring, or an improperly rated voltage supply might impact relay operation, they would not specifically explain a voltage drop across the contacts as clearly as the condition of the contacts themselves.