Portable field maintenance tool with a bus for powering and communicating with a field device

A method of communicating with a field device, the method comprising:

• communicatively connecting a field device to a communication bus disposed within a housing of a portable field maintenance tool by way of a communication interface of the portable field maintenance tool;
• and
• transmitting by the portable field maintenance tool, via the communication bus, a composite signal including:
• (i) a power signal to power the field device, and (ii) a digital amplitude modulated (AM) communication signal to communicate with the field device.

A portable field maintenance tool comprising:

• (A) a communication circuit;
• (B) a power supply;
• (C) a first set of terminals electrically connected to the communication circuit and isolated from the power supply, the first set of terminals electrically connectable to a field device to transmit to the field device a communication signal from the communication circuit without transmitting a power signal from the power supply;
• and
• (D) a second set of terminals electrically connected to the communication circuit and electrically connected to the power supply, the second set of terminals electrically connectable to the field device to transmit a composite signal including:
• (i) the communication signal from the communication circuit, and (ii) the power signal from the power supply.

A method of communicating with a field device, the method comprising:

• communicatively connecting a field device to a portable field maintenance tool that includes a communication circuit for communicating with the field device and a power supply for powering the field device;
• when the field device is connected to a first set of terminals of the portable field maintenance tool, transmitting to the field device a communication signal from the communication circuit without transmitting a power signal from the power supply;
• and
• when the field device is connected to a second set of terminals of the portable field maintenance tool, transmitting to the field device a composite signal including:
• (i) the communication signal from the communication circuit, and (ii) the power signal from the power supply.

A portable field maintenance tool comprising:

• (A) a communication interface electrically connectable to a field device located in a process control environment;
• (B) a communication bus electrically connected to the communication interface and configured to carry a composite signal including:
• (i) a communication signal transmitted to or from the field device, and (ii) bus power for powering the field device;
• (C) a switching component electrically connected to the communication bus;
• and
• (D) a power supply electrically connected to the switching component;
• wherein the switching component is actuatable to:
• (i) electrically connect the power supply to the communication bus to supply the bus power to the communication bus for powering the field device, and (ii) electrically disconnect the power supply from the communication bus to prevent the power supply from supplying the bus power to the communication bus.

A method of controlling bus power provided by a portable field maintenance tool, the method comprising:

• communicatively connecting a field device to a communication bus of a portable field maintenance tool, the communication bus configured to carry a composite signal including:
• (i) a communication signal transmitted to or from the field device, and (ii) bus power for powering the field device;
• and
• actuating a switching component that is electrically connected to both the communication bus and to a power supply of the portable field maintenance tool to:
• (i) electrically connect the power supply to the communication bus to supply the bus power to the communication bus for powering the field device, or
• (ii) electrically disconnect the power supply from the communication bus to prevent the power supply from supplying the bus power to the communication bus.

A portable field maintenance tool comprising:

• a housing;
• a communication bus disposed within the housing, the communication bus including a set of terminals that are accessible outside the housing and electrically connectable, via a wired link, to a field device;
• a communication circuit, disposed within the housing and electrically connected to the communication bus, that receives or transmits a signal to or from the field device via the communication bus;
• and
• an energy measurement circuit, disposed within the housing and electrically connected to the communication bus, that measures an electrical characteristic of the signal transmitted or received via the communication bus.

A method of communicating with a field device and monitoring signals sent or received by the field device, the method comprising:

• electrically connecting a field device to a communication bus of a portable field maintenance tool via a set of terminals of the portable file maintenance tool;
• transmitting or receiving, via the communication bus, a signal to or from the field device;
• and
• measuring an electrical characteristic of the signal transmitted or received via the communication bus.