The invention relates to a connection module for field devices in the explosion-protected area, having a housing with a plurality of controller-end terminals to connect to at least one input/output module and with field-end terminals to connect to the field devices. The connection module is characterized in that different resistors are present in the housing to provide intrinsically safe pairs of field-end terminals with different characteristic values, said resistors being hardwired in the housing to different field-end terminals and/or controller-end terminals.

An intrinsically-safe handheld field maintenance tool includes a controller, a process communication module, and a display. The process communication module is configured to communicate with a field device using a process communication protocol. The display is coupled to the controller. A user interface module is also coupled to the controller and is configured to receive user input. The controller is configured to detect a user input help request and provide a video output on the display in response to the user input help request.

A field device for process instrumentation comprises a measuring and comparison device and a readable storage element. The measuring and comparison device is configured for monitoring an operating characteristic variable for compliance with a predefined range. The readable storage element maintains a state. The storage element state is permanently changed if a value held by the operating characteristic variable goes out of said predefined range. The predefined range is determined in such a manner that, as a result of a changed state of the storage element, a loss of suitability of the field device for special operation with an operating characteristic variable with restricted specifications, but not a loss of suitability for normal operation with an operating characteristic variable with less restricted specifications, is indicated.