Communications: electrical – Continuously variable indicating – Plural transmitters
Reexamination Certificate
1999-03-30
2001-10-16
Edward, Jr., Timothy (Department: 2635)
Communications: electrical
Continuously variable indicating
Plural transmitters
C340S870020, C375S130000
Reexamination Certificate
active
06304191
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to meter reading, and, in particular, remotely reading groups of meters using a unidirectional communication system and protocol.
Utility companies are taking advantage of modem technology to reduce costs and increase efficiency in meter reading applications using wireless technology to remotely gather information from large groups of meters. Traditionally, utility meters, such as electric, water and natural gas, were manually read by utility workers visiting each meter location. Current technology allows meters to be remotely accessed from a central location through wire or wireless communication links. To further increase ease of reading and meter installation, these meters are battery powered and operate to gather parameter measurements for the respective types of meters, and various other information, and then communicate this information to a remotely situated meter reading device. Typically, large numbers of meters may be installed and configured to communicate wirelessly with a centralized remote meter reading device.
In order to keep maintenance low and operating efficiency high, it is desirable to have meters which can operate for an extended period of time without requiring maintenance, battery replacement and the like. Maintenance requirements are generally reduced by increasing battery capacity and reducing power consumption. As a result, the meters generally cycle between low-power sleep modes, to conserve energy, and full-power awake modes, when any combination of meter reading, information gathering, information processing and data transmission may occur. In order to further decrease meter cost and prolong battery life, these meters may be configured to only transmit data to the meter reading device since receiving data would result in a significant, additional toll on battery life.
In operation, the meters periodically awake from the sleep mode to gather information, such as meter parameter readings, and to check meter status. When the meter is awake, the parameter readings and meter status information may be wirelessly sent to the meter reading device and relayed on to a network or utility for processing the information.
In these applications, all of the meters located within range of the meter reading device must periodically transmit information to the meter reading device. As the number of meters increases, the likelihood of multiple meters transmitting information to the meter reading device at the same time increases. Furthermore, the frequencies at which these meters operate may likely be the same as other non-metering devices. The preferred bands are typically relatively narrow and made accessible to many different applications and technologies. Thus, there is a need for a low-cost meter and communication protocol capable of providing unidirectional communications to a remote meter reader while avoiding interference from other meters as well as other radio frequency transmissions within the communication range of the meter reading device.
SUMMARY OF THE INVENTION
The present invention provides a uni-directional protocol for communicating data from a plurality of utility meters and a meter adapted to carry out this protocol. The meters are adapted to monitor and measure the respective utility parameters which may include those for gas, water, electric or other utilities, and wirelessly download the information to a meter reading device. The protocol basically includes a synchronization pattern followed by the desired information. For a valid transmission, the synchronization pattern and subsequent data are provided in a first transmission sequence, which is immediately repeated after the end of the first sequence. Preferably, a bit is toggled during the retransmission of the transmission sequence for security.
The synchronization sequence at the beginning of each transmission sequence includes a series of 1's followed by six 0's and a final 1. The initial string of 1's identifies significant transitions of the modulation scheme while the following 0's and 1 signify the start of a new message. Preferably, the synchronization pattern is 1111111110000001. The second transmission sequence provides a robust checksum and, preferably, is an exact duplicate of the first transmission sequence with the exception of the bit toggled for security.
Each transmission sequence provides information about the meter identification indicia; version of the hardware, firmware or software; serial number; measured parameter values; and the type of utility meter being read. To reduce the risk of communication errors due to competing meters transmitting information to the remote meter reader, other RF communications and noise within the transmission field, the protocol is carried out at a non-standard baud rate, and the transmission sequences are randomly sent to minimize the risk of multiple meters awaking concurrently in a successive manner.
Transmissions are preferably on/off keyed wherein a carrier signal is turned on and off to indicate significant transitions. The period between transmissions represents the transmitted logic state. Using the carrier in this manner allows operation in a very narrow bandwidth and minimizes the risk of interference from devices using carriers in commonly used frequency bands.
Accordingly, one aspect of the present invention provides a protocol for a remote automatic meter reading system having a plurality of meters associated with communication electronics adapted to wirelessly transmit information to a remote meter reader for collection. The protocol includes: (A) providing a synchronization string including a synchronizing string for synchronizing a transmission signal and a start string for indicating the start of data being transmitted; (B) providing meter identification indicia for uniquely identifying a transmitting meter; (C) providing measurement indicia representing a parameter measured by the transmitting meter; (D) assembling a transmission sequence in a select order to provide the synchronization string followed by the meter identification indicia followed by the measurement indicia; (E) transmitting the transmission sequence; (F) modifying the transmission sequence for security; and (G) transmitting the modified transmission sequence immediately following the transmission of the transmission sequence.
The modifying step may include toggling a bit in the latter transmission sequence. Furthermore, the transmission sequence may also include software, hardware or firmware version indicia, serial numbers for the transmitting meter, meter type indicia as well as status information. Preferably, the synchronization string is 1111111110000001. The data transmitted after the synchronization string is preferably assembled and configured to not include or be arranged such that a string of 000000 occurs. Preferably, the data is transmitted by on/off keying a sinusoidal carrier frequency at a non-standard baud rate, such as 20 Kbits per second. Typically, the keying indicates significant transition for data wherein the period between transitions indicates a logic 0 or 1. The preferred carrier is 433 MHz in Europe and 457 MHz in the United States, although any RF frequency will provide satisfactory operation. The referenced frequencies are within bands in the respective countries allocated for such use. The application is especially useful when narrow band-width communication limitations are desired or required.
Another aspect of the present invention provides a utility meter adapted to wirelessly communicate with a remote meter reader to collect meter information. The meter includes metering mechanics for measuring a utility parameter and has an output providing measurement indicia. A control system with associated memory receives the measurement indicia and assembles data into a transmission sequence. The meter also includes a transmitter and antenna associated with the control system to transmit the transmission sequence. In particular, the control syste
Campbell David E.
Kiser Eric T.
,MacCord Mason PLLC
American Meter Co.
Edward, Jr. Timothy
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