Real time data processing and display system for non-linear transducers

• US 4,089,058 A
• Filed: 12/06/1976
• Issued: 05/09/1978
• Est. Priority Date: 12/06/1976
• Status: Expired due to Term

• Current Assignee: Weigh-Tronix, Inc. (Illinois Tool Works Inc.)
• Original Assignee: Control Resources, Inc.
• Inventors: Murdock, Douglas B.
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US05/747,779
• Time in Patent Office: 519 Days
• Field of Search: 235/151.3, 235/151.34, 235/92 MT, 73/4 R, 73/37, 73/80, 73/1 R, 444/1
• US Class Current: 702/91
• CPC Class Codes: G01L 1/2256 involving digital counting
• CPC Class Codes: G01L 19/083 electrical

Abstract

A system for linearizing, processing and displaying data received from a non-linear transducer. The system includes a keyboard for entering coefficients which characterize the transducer to adjust the system so that it matches the physical parameters of the transducer. The linearized data may then be processed to generate selected functions of one or more transducers before being displayed on a digital display. The system processes data in real time so that the displayed data is frequently updated. Self-monitoring circuits detect processing or operating errors in the system and generate an appropriate error indication. The system further includes means for preventing the loss of data from volatile memories in the system, as well as means for initializing the central processing unit to the first program instruction when power is removed from the system.

Claims

1. A real time system for providing a visual indication of a physical variable measured by a non-linear transducer, said physical variable being a known function of a time related characteristic of the signal at the output of said transducer, comprising:

interval counter means receiving the output of said transducer, periodically measuring the time related characteristic of said transducer output, and generating a counter output signal indicative of said time related characteristic for each measurement;

processing means receiving said counter output signal for each measurement, calculating the value of said physical variable corresponding to said time related characteristic according to said known function, and providing an output signal indicative of said physical variable; and

output means receiving the output of said processing means and providing an indication of said physical variable for each measurement.

2. The system of claim 1, further including data input means operatively associated with said processing means for manually altering said known function to correspond to the electrical characteristics of said transducer such that said system may be matched to a plurality of transducers each having a different electrical characteristic.

3. The system of claim 2, wherein said known function includes a plurality of calibration coefficients which are stored in said processing means, and wherein said data input means include:

a manually actuatable coefficient switch corresponding to each of said coefficients for selecting the calibration coefficient to be altered;

a plurality of manually actuatable data switches bearing numerical indicia including means for displaying a number on said display means corresponding to a plurality of sequentially actuated data switches;

manually actuatable switch means for clearing said number from said display; and

manually actuatable switch means for clearing the selected calibration from said processing means and for entering said number from said display means into said processing means thereby selecting a new calibration coefficient to alter the known function between said electrical characteristic and said physical variable.

4. The system of claim 2, further including a second non-linear transducer and means for alternately connecting each of said transducers to said interval counter means while automatically altering said known function to correspond to the electrical characteristics of the selected transducer, said system further including means for computing a predetermined relationship between the physical variables measured by said transducers and providing a visual indication thereof.

5. The system of claim 2, wherein said interval counter means comprise:

first counter means receiving the output of said transducer for counting the cycles of said output responsive to a first counter enable signal and for generating a stop signal after a predetermined number of said cycles have been counted during a count interval;

an oscillator generating a clock signal having a frequency substantially higher than the frequency of said transducer output signal;

second counter means receiving the clock signal from said oscillator for counting the cycles of said clock signal responsive to a second counter enable signal and for generating an electrical output signal indicative of the number of clock cycles counted; and

counter control means for generating said first and second counter enable signals responsive to a start signal and for terminating said counter enable signals responsive to said stop signal such that each count interval is divided into N timing increments where N is a relatively large number approximately equal to the product of said predetermined number and the frequency of said clock signal divided by the frequency of said transducer output signal whereby the output signal of said second counter is a relatively accurate indication of the period of said transducer output signal.

6. The system of claim 2, wherein said processing means include a volatile memory having a disable input and a central processsing unit operatively associated with said volatile memory through address and data buses, said central processing unit having a hold input for selectively suspending operation of said central processing unit and floating said address and data buses responsive to a hold signal, said system further including means for preventing data loss from said volatile memory when external power is removed from said system comprising internal power supply means supplying power to said volatile memory only when said external power is removed from said system, memory disable means operatively associated with said external power for providing a memory disable signal to said disable input for rendering said memory inoperative when external power is removed from said system, and hold signal generating means for producing said hold signal responsive to removal of external power from said system thereby floating said address and data buses as power is removed from said central processing unit to prevent spurious data from being read into said continuously operating, internally powered volatile memory.

7. The system of claim 1, further including a second non-linear transducer and means for alternating connecting each of said transducers to said internal counter means while automatically altering said known function to correspond to the electrical characteristics of the selected transducer, said system further including means for computing a predetermined relationship between the physical variables measured by said transducers and providing a visual indication thereof.

8. The system of claim 1, wherein said interval counter means comprise:

first counter means receiving the output of said transducer for counting the cycles of said output responsive to a first counter enable signal and for generating a stop signal after a predetermined number of said cycles have been counted during a count interval;

an oscillator generating a clock signal having a frequency substantially higher than the frequency of said transducer output signal;

second counter means receiving the clock signal from said oscillator for counting the cycles of said clock signal responsive to a second counter enable signal and for generating an electrical output signal indicative of the number of clock cycles; and

counter control means for generating said first and second counter enable signals responsive to a start signal and for terminating said counter enable signals responsive to said stop signal such that each count interval is divided into N timing increments where N is a relatively large number approximately equal to the product of said predetermined number and the frequency of said clock signal divided by the frequency of said transducer output signal whereby the output signal of said second counter is a relatively accurate indication of the period of said transducer signal.

9. The system of claim 8, wherein said counter control means includes means for allowing said transducer output signal to increment said first counter means one cycle of said transducer output signal after said clock signal commences incrementing said second counter means such that said predetermined number of cycles of said transducer output at which said stop signal is produced can be selected as a predetermined power of 10 thereby allowing the average period of said transducer output signal to be calculated by shifting the decimal point of the count in said second counter means at the occurrence of said stop signal a predetermined number of decimal places.

10. The system of claim 9, further including data input means operatively associated with said processing means for manually altering said known function to correspond to the electrical characteristics of said transducer such that said system may be matched to a plurality of transducers each having different electrical characteristics.

11. The system of claim 1, wherein said processing means includes a volatile memory and a central processing unit operatively associated with said volatile memory through address and data buses, said central processing unit having a hold input for selectively suspending operation of said central processing unit and floating said address and data buses responsive to a hold signal, said system further including means for preventing data loss from said volatile memory when external power is removed from said system comprising internal power supply means supplying power to said volatile memory only when said external power is removed from said system, and hold signal generating means for producing said hold signal responsive to removal of external power from said system thereby floating said address and data buses as power is removed from said central processing unit to prevent spurious data from being read into said continuously operating, internally powered volatile memory.

12. The system of claim 11, wherein said hold signal generating means comprise a hold switch mechanically operating with an external power supply switch, said hold switch removing said hold signal from said hold input when said power switch is in its on position and applying said hold signal to said hold input when said power switch is in its off position.

13. The system of claim 11, wherein said central processing unit operates in accordance with a plurality of sequentially executed program instructions selected by program counter means and wherein said central processing unit includes a reset input for initializing said program counter means to select the first program instruction responsive to a reset signal, said system further including means for initializing said program counter means upon momentary actuation of said power switch to remove power from said system, comprising a reset switch mechanically operating with said external power switch, said reset switch applying said reset signal to said reset input when said power switch is in its off position.

14. The system of claim 13, wherein said hold and reset lines are connected to a supply voltage through respective resistors, and wherein said hold and reset switches comprise a double-throw, double-pole switch having the center contact of a first pole and a first end contact of said first pole completing a power supply circuit, the center contact of a second pole connected to circuit ground, the first end contact of said second pole connected to said hold input and the second end contact of said second pole connected to said reset input such that when said switch is in a first position applying external power to said system said hold input is grounded and when said switch is in a second position removing external power from said system said reset input is grounded.

15. The system of claim 1, wherein said central processing unit operates in accordance with a plurality of sequentially executed program instructions selected by program counter means, and wherein said central processing unit includes a reset input for initializing said program counter means to select the first program instruction responsive to a reset signal, said system further including means for initializing said program counter means upon momentary actuation of said power switch to remove power from said system, comprising a reset switch mechanically operating with said external power switch, said reset switch applying said reset signal to said reset input when said power switch is in its off position.