Wetting Current Diagnostics

A circuit for diagnostic testing regarding wetting current provided to a load control switch, the circuit comprising:

• a current source coupled to a power source and configured to provide the wetting current along a path to the load control switch;
• a current sensor connected in series with the current source along the path, the current sensor being configured to generate a current sensor signal indicative of a current level along the path;
• a current measurement unit coupled to the current sensor to receive the current sensor signal, the current measurement unit being configured to implement comparisons of the current level with an open switch threshold and a closed switch threshold;
• a voltage measurement unit having an input terminal coupled to a node along the path through which the wetting current flows to reach the load control switch, the voltage measurement unit being configured to detect a state of the load control switch based on a voltage at the node;
• and
• a controller connected to the current measurement unit and the voltage measurement unit, the controller being configured to determine a wetting current diagnostic condition in accordance with the comparisons and the detected state.

A method of providing wetting current diagnostics for a load control switch, the method comprising:

• detecting a state of the load control switch;
• measuring a current level of a wetting current;
• when the detected state is an open state, determining, based on the measured current level, whether the state of the load control switch is detected correctly;
• and
• when the detected state is a closed state, comparing the measured current level to a closed switch current threshold.