Fault tolerant multipoint data collection system

• US 5,430,663 A
• Filed: 12/11/1992
• Issued: 07/04/1995
• Est. Priority Date: 12/11/1992
• Status: Expired due to Term

• Current Assignee: Mistras Holdings Corporation
• Original Assignee: Vibrametrics Incorporated
• Inventors: Judd, John E., Appley, Kenneth E., DeFrancesco, Salvatore J.
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): Wachsman, Hal D.
• Application Number:
  US07/989,187
• Time in Patent Office: 935 Days
• Field of Search: 364/550, 364/551.01, 364/551.02, 364/474.11, 364/138, 364/140, 364/132, 340/310 R, 340/310 A, 340/825.06, 340/825.07, 340/825.08, 340/825.31
• US Class Current: 702/188
• CPC Class Codes: G01D 21/02 Measuring two or more variables by means not covered by a single other subclass
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis
• CPC Class Codes: H04Q 9/14 Calling by using pulses

Abstract

A multipoint data collection system uses multiple parallel data buses connecting a central controller to addressable sensor interfaces to permit any sensor to be connected to a central controller over any one of the data buses. Faults on a data bus may be bypassed, or multiple sensors monitored simultaneously in real time, through the use of the parallel data buses. Digital address signals and analog data are transmitted on the same data bus, distinguished from one another by restricting the voltage range of the analog data to voltages above the voltage corresponding to a digital zero and below the voltage corresponding to a digital one.

Claims

1. A multipoint data collection system comprising:

a plurality of parallel data buses organized into a single cable, each data bus being adapted to carry data independently of each other data bus;

a central controller including a plurality of bus interface means each being connected to a corresponding one of the data buses, the central controller being adapted to send an address signal to a plurality of sensor interfaces, the address signal including a sensor address identifying a selected sensor interface and a bus address identifying a selected one of the parallel data buses from among the plurality of parallel data buses; and

the plurality of sensor interfaces, each being connected to more than one of the parallel data buses in the cable and to a corresponding sensor and each having a unique sensor address, each sensor interface including address means responsive to the address signal for connecting the corresponding sensor to the selected one of the parallel data buses specified in the bus address of the address signal when the unique sensor address of the corresponding sensor matches the sensor address specified in the address signal to send data from the corresponding sensor to the central controller over the selected one of the parallel data buses.

2. A multipoint data collection system according to claim 1 wherein the cable further includes a keep-alive power bus, each of the sensor interfaces being powered by the keep-alive power bus.

3. A multipoint data collection system according to claim 1 wherein the central controller further includes sensor power means for applying sensor power to the selected sensor interface over the selected one of the parallel data buses.

4. A multipoint data collection system according to claim 3 wherein the sensor power means provides sensor power to generate analog data within a restricted voltage range, and the address signal is a digital signal having voltages corresponding to ones and zeros that are outside of the restricted voltage range.

5. A multipoint data collection system according to claim 4 wherein the selected sensor interface includes an address detector that detects addresses by detecting voltages outside of the restricted voltage range.

6. A multipoint data collection system according to claim 3 wherein the central controller further includes a timer means for signaling the sensor power means to apply sensor power to the selected data bus after the address signal identifying the selected sensor interface and the selected one of the parallel data buses has been sent.

7. A multipoint data collection system according to claim 1 wherein the central controller further includes an input means for selecting a desired sensor.

8. A multipoint data collection system according to claim 1 wherein the central controller further includes a status output means for signaling a status of operation of the central controller.

9. A multipoint data collection system according to claim 1 wherein the central controller further includes a plurality of data output means, each data output means being connected to a corresponding one of the parallel data buses.

10. A multipoint data collection system according to claim 1 wherein each sensor interface further includes reset circuit means for disconnecting the sensor from the selected data bus.

11. A multipoint data collection system according to claim 10 wherein the central controller further includes sensor power means for applying and removing sensor power to and from the selected sensor interface over the selected one of the parallel data buses, and the sensor interface means for disconnecting the sensor from the selected one of the parallel data buses operates in response to a removal of sensor power from the selected one of the parallel data buses.

12. A multipoint data collection system according to claim 11 wherein the sensor power means comprises a constant current source which powers the sensor corresponding to the selected sensor interface to send analog data on the selected one of the parallel data buses.

13. A multipoint data collection system according to claim 12 wherein the address signal is a binary digital signal having a higher voltage and a lower voltage, one of said voltages corresponding to a binary one and the other of said voltages corresponding to a binary zero, the higher voltage being greater than the maximum voltage available from the sensor power means.

14. A multipoint data collection system according to claim 1 wherein the address signal is a digital signal composed of data bits and clock bits, each bit of the address signal being preceded by a clock bit.

15. A multipoint data collection system according to claim 1 wherein the address signal is composed of a sensor address and a bus address.

16. A multipoint data collection system according to claim 1 wherein a plurality of sensor interfaces are organized into a multiple sensor distribution box, the plurality of sensor interfaces being connected to the parallel data buses through a common connector and a plurality of sensors being connected to the sensor interfaces in the multiple sensor distribution box.

17. A multipoint data collection system according to claim 1 further including a sensor power means remotely located from the central controller.

18. A multipoint data collection system according to claim 1 wherein each bus interface means includes an auxiliary connection for making a DC connection to the selected one of the parallel data buses connected to the bus interface.

19. A multipoint data collection system according to claim 1 wherein at least one sensor interface is located within a housing also enclosing a sensor.

20. A multipoint data collection system comprising:

a plurality of data buses organized into a cable, each data bus having a corresponding bus address and each data bus being adapted to carry data independently of each other data bus;

a central controller including;

an input means for selecting a sensor from which data is to be collected,

a microcontroller responsive to the input means for generating an address signal including a sensor address corresponding to the selected sensor and a bus address specifying a selected data bus over which the data should be transmitted,

a data output means for outputting data received from the selected sensor, and

a plurality of bus interfaces corresponding to the plurality of data buses, each bus interface being connected to the corresponding data bus and to the microcontroller and including;

address means for placing the address signal onto the corresponding data bus connected to the bus interface,

sensor power means for applying sensor power to the corresponding data bus connected to the bus interface; and

a plurality of sensor interfaces adapted for connection at spaced locations along the cable, each sensor interface being connected to the plurality of data buses and to a corresponding sensor, each sensor interface comprising;

means for storing a unique sensor address,

an address detector connected to the plurality of data buses,

an address comparator, responsive to the address detector, producing a bus select output signal corresponding to the bus address upon receipt of a sensor address from the address detector that matches the unique identifying sensor address,

a bus select means, responsive to the bus select output signal of the address comparator, for connecting the sensor to the selected one of the data buses specified in the bus address, and

reset means for disconnecting the sensor from the selected data bus.

21. A multipoint data collection system according to claim 20 wherein the reset means for disconnecting the sensor from the selected one of the parallel data buses disconnects the sensor whenever the voltage on the address bus drops to a value below a predetermined reference voltage.

22. A multipoint data collection system according to claim 20 wherein a plurality of sensor interfaces are organized into a multiple sensor distribution box, the plurality of sensor interfaces being connected to the data buses through a common connector and a plurality of sensors being connected to the plurality of sensor interfaces in the multiple sensor distribution box.

23. A multipoint data collection system according to claim 20 wherein the sensor power means provides sensor power to generate analog data within a restricted voltage range, and the address signal is a digital signal having voltages corresponding to ones and zeros that are outside of the restricted voltage range.

24. A multipoint data collection system according to claim 23 wherein the address detector detects addresses by detecting voltages outside of the restricted voltage range.

25. A multipoint data collection system comprising:

at least one data bus having a plurality of connection points at spaced locations along the length of the at least one data bus;

a central controller including a bus interface means connected to the at least one data bus for sending a digital address signal on the at least one data bus identifying a selected sensor interface;

a plurality of sensors producing analog sensor data; and

a plurality of sensor interfaces, corresponding to the plurality of sensors, adapted for connection to a at least one data bus and to the corresponding sensor and each including;

means for storing a unique address,

address means responsive to the digital address signal to produce a match signal when the unique address is included in the digital address signal,

switch means closing in response to the match signal to connect the corresponding sensor to the at least one data bus to send analog sensor data to the central controller over the at least one data bus, and

reset means for opening the switch means to disconnect the corresponding sensor from the at least one data bus.

26. A multipoint data collection system according to claim 25 wherein the reset means includes a voltage comparator responsive to a drop in voltage on the at least one data bus below a reference voltage to open the switch means and disconnect the corresponding sensor from the at least one data bus.

27. A multipoint data collection system according to claim 26 wherein the corresponding sensor produces analog data having a voltage which is greater than the reference voltage in the reset means.