The B863–032 monitored dc input module (B863) is a 32 point, 24 Vdc, true high, 800 Series, module capable of determining the state of switches, relays, solenoids, lamps, proximity switches, and other 24 Vdc powered devices. In addition, the B863–032 monitors itself to insure its ability to detect high or low states at its inputs.
This feature is designed to provide an extra margin of reliability in safety shutdown systems. This is accomplished with a module resident diagnostic test. The diagnostics verify the module’s functionality by momentarily forcing all inputs to a low state followed by a high state. This forcing function is transparent to the input source.
Following is a simplified schematic of the B863–032 monitored 24 Vdc input module.
This diagnostic test is performed at a rate of 1/s, and takes less than 1 ms. The inability of an input to detect a low or high state during diagnostics, results in the reporting of a fault to the controller, and the flashing of the active LED. Digital filtering is performed on all inputs to reduce the occurrence of nuisance faults. Communication between the module and the controller consists of four words. Two words contain the state of each input, and the other two words contain the fault status of each input. Within the state words, a high, or one indicates a on condition. Within the fault status words, a high, or one indicates a fault at the respective input.
