Browse Prior Art Database

Two Wire Mass Flow Meter

IP.com Disclosure Number: IPCOM000171129D
Published in the IP.com Journal: Volume 8 Issue 6A (2008-06-09)
Included in the Prior Art Database: 2008-Jun-09
Document File: 2 page(s) / 30K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Flow meters are used to measure the mass flow rate, density, and other characteristics of flowing materials. The flowing materials can comprise liquids, gases, combined liquids and gases, solids suspended in liquids, and liquids including gases and suspended solids. For example, a flow meter can be used to determine well production by measuring a flow rate (i.e., by measuring a mass flow through the flow meter), and can even be used to determine the relative proportions of the gas and liquid components of a flow. A standardized instrumentation fieldbus is typically used to connect together multiple instruments, such as flow meters, and is further capable of being used to provide digital communications between instruments. In addition, a fieldbus barrier device can pass digital communication signals to external devices, such as to monitoring and control stations, for example. The bus barrier device is connected to an electrical power source and provides electrical power over the wire bus.

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Two Wire Mass Flow Meter

Idea: Henning Max Hansen, DK-Norborg; Allan Juhl Kristensen, DK-Norborg

Flow meters are used to measure the mass flow rate, density, and other characteristics of flowing materials. The flowing materials can comprise liquids, gases, combined liquids and gases, solids suspended in liquids, and liquids including gases and suspended solids. For example, a flow meter can be used to determine well production by measuring a flow rate (i.e., by measuring a mass flow through the flow meter), and can even be used to determine the relative proportions of the gas and liquid components of a flow.

A standardized instrumentation fieldbus is typically used to connect together multiple instruments, such as flow meters, and is further capable of being used to provide digital communications between instruments. In addition, a fieldbus barrier device can pass digital communication signals to external devices, such as to monitoring and control stations, for example. The bus barrier device is connected to an electrical power source and provides electrical power over the wire bus.

Known are systems with three power supplies each supplying current to sensor subsystems such as the communication system or the processor, the signal processor or the driver circuit. The term power supply in this context refers to an active circuit that controls a voltage. The principle is known from e.g. pressure transmitters with the exception that only two power supplies are necessary or even one power supply can be sufficient. The power supply is usually made as a current generator set to provide the maximal current used by the measurement system and the bus driver. The supply voltage is then held constant by a shunt zener diode. In magnetic (MAG) and mass (MASS) flow meter transmitters it has usually been necessary to split the drive power and the signal processor power supplies because of a high demand for the separation of drive and sensor signals. In order to make an intrinsically safe transmission of the bus signals it is necessary to have a separate supply for the bus driver. Hence whenever the transmitter is made for two wires there will be a need for three power supplies.

In the following a novel power supply method for a two or more wire bus instrument will be presented, where the communication is placed as changing current on top of the supply voltage. In consideration of the fact that the power supplies for driver and signal processing must provide a substantially constant voltage, a combination of d...