| 摘要 |
<p>An unknown series resistance 160a,b in a circuit, such as a fire alarm circuit, is measured by: connecting the circuit to a charged capacitor 211; measuring the voltage across the load terminals 301a,b; forcing a known current through the circuit and, whilst forcing the known current, measuring the voltage across the load at two points in time; using these measured voltages to derive, by extrapolation, the voltage across the load at an earlier time at which current was being forced across the load; determining the difference between the derived voltage at the earlier point in time and the voltage when no current is forced across the load; and using this difference and the known current to determine the unknown series resistance. The method may be implemented by an end of line device 300. The capacitor may be connected across the terminals of a power supply to which the circuit is connected 110.</p> |
