Why might a multimeter read voltage correctly but fail to read milliamp current?

A multimeter can read voltage correctly but fail to read milliamp current due to a blown current fuse within the meter. Multimeters typically have separate fuses for different functions, such as voltage and current. The current fuse is specifically designed to protect the multimeter's circuitry when measuring current. If this fuse is blown, the meter cannot complete the circuit necessary to measure current, resulting in a failure to read milliamp levels accurately. However, since measuring voltage does not rely on the current fuse, the meter continues to provide correct voltage readings.

In this scenario, even if the leads are functioning and connected properly, the blown current fuse interrupts the flow of current, making the current measurement impossible while allowing voltage measurements to continue. This concept is essential for instrument technicians to understand, as it highlights the need for proper maintenance and troubleshooting of their equipment.