Abstract: A communication apparatus is provided. The apparatus includes a printed circuit board having a thickness that complies with an intrinsic safety physical separation specification. A first pair of capacitive plates are disposed on opposite sides of the printed circuit board and are arranged to form a first capacitor having an insulating layer of the printed circuit board forming a dielectric material for the first capacitor. A second pair of capacitive plates are disposed on opposite sides of the printed circuit board and are arranged to form a second capacitor having the insulating layer of the printed circuit board forming a dielectric material for the second capacitor. A modulator is coupled to the first and second capacitors and is configured to receive an input signal having an input signal frequency and to provide a modulated signal having a frequency that is higher than the input signal.

Abstract: A wireless adapter for use in a two-wire process control loop includes wireless communication circuitry and first and second terminals configured to couple in series with the two-wire process control loop. A regulator having a regulated input is coupled to the first terminal and an output. A shunt is coupled to the output of the regulator and is configured to provide power to the wireless communication circuitry. A feedback circuit is configured to control current flowing from the regulator to the shunt as a function of a loop current flowing through the two-wire process control loop.

Abstract: An adapter for coupling to a process control transmitter of the type used to monitor a process variable in an industrial process includes a first connection configured to couple to a first side of a two wire process control loop, a second connection configured to couple to a second side of the two wire process control loop and in series with a first connection to a process control transmitter, and a third connection configured to couple to a second connection of the process control transmitter. Wireless communication circuitry is coupled to at least the third connection and is configured to provide wireless communication for the process control transmitter. Intrinsic safety circuitry coupled to at least one of the first, second and third connections is configured to limit transfer of electrical energy to a value which is less than an intrinsic safety value.

Abstract: An adapter for coupling to a process control transmitter of the type used to monitor a process variable in an industrial process is provided. The adapter includes I/O circuitry configured to couple to a two wire process control loop and to the process control transmitter and communicate on the process control loop. Wireless communication circuitry couples to the two wire process control loop and is configured to transmit an RF signal. Power supply circuitry provides power to the wireless communication circuitry.

Abstract: A wireless adapter for use with a two-wire process control loop is configured to couple to a process field device in an industrial process control system. The wireless adapter is coupled to the two-wire process control loop and provides wireless communication to the process field device. The adapter includes first and second loop terminals configured to couple in series with the two-wire process control loop. Wireless communication circuitry is coupled to the first and second loop terminals and is adapted to provide wireless communication to the process field device. Loop current bypass circuitry is electrically connected between the first and second loop terminals and is configured to provide a loop current path therebetween in response to an open circuit in wireless communication circuitry.

Abstract: A wireless adapter for use in a two-wire process control loop includes wireless communication circuitry and first and second terminals configured to couple in series with the two-wire process control loop. A regulator having a regulated input is coupled to the first terminal and an output. A shunt is coupled to the output of the regulator and is configured to provide power to the wireless communication circuitry. A feedback circuit is configured to control current flowing from the regulator to the shunt as a function of a loop current flowing through the two-wire process control loop.

Abstract: A wireless adapter for use with a two-wire process control loop is configured to couple to a process field device in an industrial process control system. The wireless adapter is coupled to the two-wire process control loop and provides wireless communication to the process field device. The adapter includes first and second loop terminals configured to couple in series with the two-wire process control loop. Wireless communication circuitry is coupled to the first and second loop terminals and is adapted to provide wireless communication to the process field device. Loop current bypass circuitry is electrically connected between the first and second loop terminals and is configured to provide a loop current path therebetween in response to an open circuit in wireless communication circuitry.

Abstract: An adapter for coupling to a process control transmitter of the type used to monitor a process variable in an industrial process includes a first connection configured to couple to a first side of a two wire process control loop, a second connection configured to couple to a second side of the two wire process control loop and in series with a first connection to a process control transmitter, and a third connection configured to couple to a second connection of the process control transmitter. Wireless communication circuitry is coupled to at least the third connection and is configured to provide wireless communication for the process control transmitter. Intrinsic safety circuitry coupled to at least one of the first, second and third connections is configured to limit transfer of electrical energy to a value which is less than an intrinsic safety value.

Abstract: An adapter for coupling to a process control transmitter of the type used to monitor a process variable in an industrial process is provided. The adapter includes I/O circuitry configured to couple to a two wire process control loop and to the process control transmitter and communicate on the process control loop. Wireless communication circuitry couples to the two wire process control loop and is configured to transmit an RF signal. Power supply circuitry provides power to the wireless communication circuitry.

Abstract: A level transmitter for use in a process application measures height of a product in a tank. The level transmitter includes a microwave antenna directed into the tank. A low power microwave source sends a microwave signal through the microwave antenna. A low power microwave receiver receives a reflected microwave signal. Measurement circuitry coupled to the source and receiver initiates transmitting of the microwave signal and determines product height based upon the received, reflected signal. Output circuitry coupled to a two-wire process control loop transmits information related to product height over the loop. Power supply circuitry in the level transmitter coupled to the two-wire process control loop receives power from the loop which powers the level transmitter including the microwave source and the microwave receiver.

Abstract: A radar gauge adapted to sense fluid level in a tank and including a radar gauge circuit in which radar transmission and level sampling are controlled by a transmit frequency and a sample frequency respectively. A first frequency separation between first and second frequencies is controlled by a control input. The first and second frequencies can be divided to generate the transmit and sample frequencies, separated by a second frequency separation. At least one frequency difference is evaluated and the evaluation used to generate the control input, stabilizing the first frequency difference, and to correct the gauge output.

Abstract: A direct current (DC) powered process instrument start up circuit includes an energy storage device, a switching regulator circuit, a variable impedance circuit, and a voltage measurement circuit. The energy storage device is coupled between first and second power supply terminals. The switching regulator circuit is coupled to the energy storage device and has a regulated voltage output. The variable impedance circuit is coupled between the energy storage device and the first power supply terminal and has an impedance control input. The voltage measurement circuit has a measurement input coupled to the energy storage device and a measurement output coupled to the impedance control input.

Abstract: A level sensor for use in a process application measures height of a product in a tank. The level meter includes a microwave feedhorn directed into the tank, an electronics housing spaced apart from the feedhorn and a microwave waveguide extending therebetween. A microwave transducer in the housing couples to the waveguide and sends and receives microwave signals. A microprocessor in the housing identifies echoes from the microwave signals which are generated and sensed by the microwave transducer. The microprocessor determines height of the product based upon a microwave echo from the product and a microwave echo from the feedhorn. The microprocessor compensates for the effect of propagation delay through the waveguide on height measurements with the feedhorn echo and provides an output related to height of the product in the tank.

Abstract: A barrier device threadably mounts to a cabling aperture on a field mounted transmitter. The field mounted transmitter receives and transmits signals, and is wholly powered by a current loop circuit. The barrier device has a conductive housing with at least a first and a second aperture and a pair of conductors passing through the first aperture of the barrier device, for connecting to a terminal block in the transmitter. A pair of signal terminals, preferably as ring tongue lug, is mounted in the second aperture of the barrier device. The signal terminals are connectable to a handheld communicator, which is used to calibrate, monitor and test the transmitter. A barrier circuit is mounted in the housing and is electrically connected between the signal terminals and the conductors. Signals from the communicator access the terminal block through the barrier circuit, and the barrier circuit limits the power available at the signal terminals.

Abstract: A level transmitter for use in a process application measures height of a product in a tank. The level transmitter includes a microwave antenna directed into the tank. A low power microwave source sends a microwave signal through the microwave antenna. A low power microwave receiver receives a reflected microwave signal. Measurement circuitry coupled to the source and receiver initiates transmitting of the microwave signal and determines product height based upon the received, reflected signal. Output circuitry coupled to a two-wire process control loop transmits information related to product height over the loop. Power supply circuitry in the level transmitter coupled to the two-wire process control loop receives power from the loop which powers the level transmitter including the microwave source and the microwave receiver.

Abstract: An existing analog two-wire transmitter has a sensor module, an analog excitation circuit, and an analog detector circuit which provides an output representative of a sensed process variable, such as pressure, to a two-wire current loop. The analog detection circuit is removed and replaced with apparatus including a digital converter that digitally calculates the transmitter's output. The output is improved by calculating correction for linearity. The analog excitation circuit may also be replaced with a replacement excitation circuit. The replacement excitation circuit and the digital converter can be energized in series to control energization current. A charge pump can be coupled to the loop to balance the current in the series circuit. The digital converter can also provide electrical span and zero adjustments.

Abstract: A cold junction compensation bridge for a thermocouple circuit includes a temperature compensation resistor encased in a heat conductive material and is directly connected to the same terminal block or strip to which the thermocouple leads are attached. The compensation resistor is in the same chamber of a housing as the cold junction of the thermocouple so it is subjected to the same temperature as the thermocouple junction. This is of particular importance in two wire current transmitters wherein the housings are multi compartment, with the electronics in one compartment (that may be sealed and not normally opened) and the terminal blocks for connecting the thermocouple and the like, as well as the calibrating screws, in a separate compartment. In such arrangements the thermocouple cold junction can be at a different temperature than the rest of the electronics.

Abstract: A radar gauge adapted to sense fluid level in a tank and including a radar gauge circuit in which radar transmission and level sampling are controlled by a transmit frequency and a sample frequency respectively. A first frequency separation between first and second frequencies is controlled by a control input. The first and second frequencies can be divided to generate the transmit and sample frequencies, separated by a second frequency separation. At least one frequency difference is evaluated and the evaluation used to generate the control input, stabilizing the first frequency difference, and to correct the gauge output.