Staking and soldering are eliminated to improve workability in assembly. The first measuring apparatus includes a first sensing device having a sensing field for obtaining positional data of a first testing target, a calibration target rigidly linked to the first sensing device, wherein the positional relationship between the first sensing device and the calibration target is known. The enclosure panel comprises a top portion, a pair of side portions, an end portion, and a bottom portion. The threshold level of detection current is regulated based on the measured level the detection current without flowing therethrough a large amount of current nor implementing any additional device. The same scheme can be extended to shared interrupts, where multiple devices share a single interrupt line. This invention further relates to methods for producing maize varieties derived from maize variety X18A635.