Hi,
Galvanic skin response aka GSR, is a method of measuring the electrical conductance of the skin. Strong emotion can cause a stimulus to your sympathetic nervous system, resulting in more sweat being secreted by the sweat glands.
The response can take seconds to arise and longer to decay. However, you can experiment with thinking of exciting or calming thoughts and watch how your galvactivator responds. Once you have dialed it to your proper baseline, the galvactivator should be sensitive enough to respond to internally-generated imagery in a broad way.