Communications: electrical – Continuously variable indicating – With meter reading
Reexamination Certificate
1999-09-28
2001-01-09
Horabik, Michael (Department: 2635)
Communications: electrical
Continuously variable indicating
With meter reading
C340S870160, C340S870030
Reexamination Certificate
active
06172615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communicator for field instruments which is connected to a transmission line which connects the field instruments to a host instrument in order to perform communication between the field instruments and the host instrument. The invention also relates to a method of supplying power to the communicator.
2. Description of the Related Art
Instruments known as field instruments have a great variety of sensors incorporated in them, and measure physical quantities, such as pressure, temperature, and flow rate in various plants. They transmit such physical measurements to a host instrument over a transmission line, after having converted the physical quantities into electric signals. The transmission of these electric signals has been standardized. The field instruments output analog current signals of 4-20 mA to the transmission line, and the host instrument receives the analog current signals. The analog signals are transmitted from the field instruments to the host instrument in a one-way communication.
Because of improvements in the technique of manufacturing semiconductor ICs, field instruments incorporating microprocessors have been developed and put into practical use in recent years. The field instrument performs two-way communication in digital signals, rather than one-way communication in analog signals as over the above-mentioned transmission line, and is capable of performing processes such as range setting and self-diagnosis of the field instrument even from a remote place. The field instrument also communicates with a communicator exclusively in digital signals, this communicator being connected to any place along the transmission line. A device of this type is disclosed, for example, in Japanese Patent Laid-Open No. 59-201535.
In the conventional example mentioned above, as a method of transmitting signals over the transmission line, digital signals are carried on analog signals for simultaneous communication. In addition to this method, there is a method in which analog signals are switched over to digital signals for communication. There is also a method in which communication is performed solely in digital signals.
In these conventional examples, the communicator has a built-in power supply such as a battery, and is constructed so as to operate all the built-in circuits on the electric power fed from the built-in power supply. For this reason, it is required to carry out maintenance, such as replacing or charging the built-in battery, after the built-in battery has been used for a predetermined period.
The above-described conventional art, however, does not take into consideration where the communicator is continuously used for a long period of time for trouble-shooting the field instrument or the like. In other words, there is a problem in that since the service time of the power supply incorporated in the communicator is limited, it is impossible to continuously monitor values, such as output values and internal status of the field instrument for prolonged periods.
Furthermore, the communicator is not always utilized in an instrument room, but may also be connected to any place along the transmission line for outdoor use. In such a case, when the capacity of the built-in power supply runs out during its service, the built-in power supply must be replaced or charged. This leads to a problem in that maintenance, such as replacing or charging the built-in power supply, becomes troublesome.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a communicator for field instruments which can be continuously used for prolonged periods, and which reduces the frequency of maintenance, and to provide a method of supplying power to this communicator.
In order to achieve the foregoing object, the present invention provides a communicator for field instruments which is connected to a transmission line for transmitting electric signals from the field instruments to a host instrument, and which operates on electric power fed from an external power supply over the transmission line.
The invention further provides a communicator for field instruments which is connected to a two-wired transmission line for transmitting electric signals from the field instruments to a host instrument, and which operates on electric power fed from an external power supply over the transmission line.
Furthermore, the invention provides a communicator for field instruments which is connected to the ends of a voltage drop element arranged in series in a transmission line which connects the field instruments to a host instrument, and the communicator operates on electric power fed from an external power supply over the transmission line.
Moreover, the invention provides a communicator for field instruments which is connected in series to any place along the transmission loop of a transmission line which connects the field instruments to a host instrument, and the communicator operates on electric power fed from an external power supply over the transmission line.
In addition, the invention provides a communicator for field instruments connected to a transmission line which connects a plurality of field instruments connected in a parallel manner to a host instrument, and the communicator operates on electric power fed from an external power supply over the transmission line.
According to the present invention, there is provided a communicator for field instruments connected to a two-wired transmission line which connects a plurality of field instruments connected in a parallel manner to a host instrument, wherein the communicator operates on electric power fed from an external power supply over the two-wired transmission line.
According to the invention, there is also provided a communicator for field instruments connected to the ends of a voltage drop element when the voltage drop element is arranged in series in a transmission line which connects a plurality of field instruments connected in a parallel manner to a host instrument, and the communicator operates on electric power fed from an external power supply over the transmission line.
According to the invention, there is further provided a communicator for field instruments which is connected in series to any place along the transmission loop of a transmission line which connects a plurality of field instruments connected in a parallel manner to a host instrument, and the communicator operates on electric power fed from an external power supply over the transmission line.
The present invention provides a plant monitoring system including: a field instrument for measuring physical quantities of a plant; a host instrument for receiving detected signals from the field instrument over a transmission line; a communicator for performing communication between the field instrument and the host instrument; a host controller for controlling the plant based on signals from the host instrument; and a power supply arranged in the transmission line so as to operate the communicator.
The present invention further provides a plant monitoring system connected in parallel to a commonly used transmission line, including: a plurality of field instruments for measuring physical quantities of a plant; a field instrument for receiving detected signals from the field instruments over the transmission line; a communicator for performing communication between the field instruments and the host instrument; a host controller for controlling the plant based on signals from the host instrument; and a power supply arranged in the transmission line so as to operate the communicator.
Moreover, the invention provides a method of supplying power to a communicator for field instruments, wherein the communicator is connected to any place along a transmission line over which electric signals are transmitted from the field instrument to a host instrument, and when communication is performed among the field instruments, the host instrument, and the communicator, electric
Antonelli Terry Stout & Kraus LLP
Edwards, Jr. Timothy
Hitachi , Ltd.
Horabik Michael
LandOfFree
Communicator for field instruments and method of supplying... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Communicator for field instruments and method of supplying..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Communicator for field instruments and method of supplying... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438973