LOOP SYSTEM SENSITIVITY
Loop system sensitivity is defined as the smallest change of inductance at the electronics unit terminals that will cause the controller to actuate. This sensitivity must be equal to or greater than the threshold for the electronics unit. Many states specify that the electronics unit must respond to a 0.02 percent change in inductance. NEMA Standards (see Section 15.3.2 of
Appendix J), recognizing the differences in electronics unit design (
L/L or
L), specify the sensitivity threshold for three classifications of test vehicles when they are centered in a single 6- x 6-ft (1.8- x 1.8-m) three-turn loop with 100 ft (30.5 m) of lead-in cable. The vehicle classes are: