I am looking into using the $DCSS_CLLB[1].$EXT_FORCE[3] variable in my application. I am fairly confident that it gives the wrench (forces and moments) at the TCP. However what I can't figure out is what frame it is in, and why it is zero on start up. Whenever I power cycle the robot in different configurations, the values are always zero when the robot starts up. Even if they were not zero when the robot was powered off. Are these values always relative to the wrench the TCP experienced on startup?