Universal microcomputer for individual sensors

• US 4,562,554 A
• Filed: 06/09/1983
• Issued: 12/31/1985
• Est. Priority Date: 06/09/1983
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Stixrud, Thomas E., Sotirin, Barbara
• Primary Examiner(s): Thomas, James D.
• Assistant Examiner(s): Munteanu, Florin
• Application Number:
  US06/502,797
• Time in Patent Office: 936 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 364/551, 364/556, 364/557, 323/370, 323/371, 377/20, 377/25, 307/152, 307/153
• US Class Current: 712/36
• CPC Class Codes: G01D 21/02 Measuring two or more variables by means not covered by a single other subclass
• CPC Class Codes: G01D 9/005 Solid-state data loggers

Abstract

This invention is an apparatus and method created around a specialized micomputer attachable to and addressable to each thermister in an array of thermisters used to measure temperature in the sea. The invention provides a number of options so that the same model of microcomputer can be adapted to several different modes of operation and used to monitor a variety of other sensors that have electrical resistance, voltage or current as outputs. Alternate modes of operation for resistive sensors are presented where a number that fixes the measurement as a fraction of the dynamic range of the variable being measured is determined. The system includes the circuits and memory needed to adapt it to any of a variety of sensors measuring physical quantities. The microcomputer contains a counter that can be incremented at several rates, a voltage comparator which can be used to interrupt the counter at a number that represents the measurement, input/output buffers for connections with a remote master control unit whereby command instructions and data can be relayed to and from the microcomputer, and a voltage reference source.

Claims

1. A universal microcomputer circuit for dedicated monitoring of individual sensors in an array of sensors, wherein a separate universal microcomputer is connected to each of said sensors in the chain, said universal microcomputer comprising:

a central processing unit;

memory means connected to the central processing unit, said memory means containing instructions and data;

means connected to the central processing unit for controlling timing of the circuit;

means for accumulating a count;

first buffering means connected between the central processing unit and a control input for buffering command signals coming in through the control input from a master control unit, said buffering means also connected to the means for accumulating a count;

second buffering means connected between the central processing unit and a data output terminal for buffering the data output from the central processing unit to the master control unit;

comparing means connected with its output to the central processing unit, for comparing a voltage difference between two inputs to said comparing means;

a voltage reference connected to a first input of said comparing means;

a sensor circuit connected with its first end to the central processing unit and the first buffering means, and with its second end having a voltage output connected to a second input to the comparing means.

2. An apparatus according to claim 1 wherein the memory means comprises:

a read only memory.

3. An apparatus according to claim 2 wherein the means for accumulating a count comprises:

a plurality of sixteen-bit count accumulators.

4. An apparatus according to claim 3 wherein the first buffering means comprises:

a dual buffer and divider circuit.

5. An apparatus according to claim 4 wherein the second buffering means comprises:

a serial/parallel formatter and output buffering circuit.

6. An apparatus according to claim 5 wherein the sensor circuit further comprises:

a resistive element sensor with its first end connected to the central processing unit to receive power and operational control during measurement, and its second end connected to the second input of the comparing means; and

a capacitor connected with its first side at ground potential and its second side connected to the second input of the comparing means.

7. An apparatus according to claim 5 wherein the sensor circuit further comprises:

a resistive element sensor connected with its first end to the central processing unit and its second end to the second input of the comparing means;

a lower limit resistor connected with its first end to the central processing unit and its second end to the second input of the comparing means;

an upper limit resistor connected with its first end to the central processing unit and its second end to the second input of the comparing means; and

a capacitor with its first side connected to ground and its second side connected to the second input of the comparing means.

8. An apparatus according to claim 5 wherein the sensor circuit further comprises:

a resistive element sensor connected with its first end to the central processing unit and its second end connected to the first input of the comparing means, said second end also connected to the central processing unit whereby power may be selectively applied to this end of said resistive element sensor;

an upper limit resistor with its first end connected to the central processing unit and its second end connected to the first input of the comparing means, said second end also connected to the central processing unit whereby power may be selectively applied to this end of said upper limit resistor;

a lower limit resistor with its first end connected to the central processing unit and its second end connected to the second input of the comparing means, said second end also connected to the central processing unit whereby power may be selectively applied to this end of said lower limit resistor;

a capacitor with its first side connected to the second end of the lower limit resistor and to the second input of the comparing means, and with its second side connected to the first input of the comparing means, said second side of the capacitor also being connected to a terminal of the central processing unit wherein power can be selectively generated on this terminal.

9. An apparatus according to claim 5 wherein the sensor circuit further comprises:

a first input terminal to receive a positive voltage;

a first resistor connected to said first input terminal on its first end, and connected at its second end to the first input of the comparing means, said second end also connected to a first terminal of the central processing unit whereby power or impedance can be selectively applied;

a second input terminal to receive a negative voltage;

a second resistor connected to the second input terminal to receive a negative voltage at its first end and connected at its second end to the second input of the comparing means, said second end also connected to a second terminal of the central processsing unit whereby power or impedance can be selectively applied; and

a capacitor connected between the second ends of the first and second resistors.

10. An apparatus according to claim 5 wherein the sensor circuit further comprises:

an input terminal to receive a positive voltage;

a resistor with its first end connected to the positive input terminal, and its second end connected to the first input of the comparing means, said second end also connected to a terminal of the central processing unit whereby impedance levels or power can be selectively applied; and

a capacitor connected between the second end of the resistor and ground.

11. An apparatus according to claim 5 wherein the universal microcomputer circuit further includes an amplifying circuit which comprises:

means for amplifying a sensor signal, said means containing input terminals for connection to the individual sensors and output terminals for connection to the sensor circuit; and

a programmable gain decoder connected to the amplifying means whereby the amount of gain can be programmed in a preselected manner.

12. An apparatus according to claim 11 wherein the universal microcomputer circuit further includes a low pass filter circuit which comprises:

a programmable low pass filter with input and output connections for attachment in the sensor circuit, and with filter control connections for connection with the master control unit for preprogramming the operating conditions of said filter.

13. An apparatus according to claim 5 wherein the universal microcomputer circuit further comprises:

an electrical connection cable of preselected length attached at one end to a power port, to a data output port, and a control input port of the microcomputer circuit; and

the master control unit located at a remote preselected distance, said master control unit being connected to the other end of the electrical cable, said master control unit being selectively set to send command instructions to the universal microcomputer circuit, and also to receive data transmitted from said universal microcomputer circuits.

14. An apparatus according to claim 13 wherein said master control unit further comprises:

connections through a transmission cable to a plurality of universal microcomputer circuits which are each attached to a single sensor circuit.

15. An apparatus according to claim 5 wherein the memory means comprises:

an erasable programmable read only memory.

16. A method using a universal microcomputer circuit according to claim 6 which comprises the steps of:

charging a capacitor through a series connected variable resistive element sensor;

accumulating a numerical count proportional to the elapsed time during the charging step;

monitoring the voltage at a point located between the variable resistive element sensor and the capacitor, said monitored voltage being fed to a first input terminal of a comparator;

feeding a preset reference voltage to the second input of said comparator;

comparing the two input voltages with said comparator;

stopping the accumulating numerical count when the compared voltages are equal, whereby said count represents the time to charge the resistance-capacitance circuit to the reference voltage level which in turn is dependent upon the variable value of the resistive sensor;

processing the accumulated numerical count value to obtain the value of the resistance for the variable resistive element; and

converting the value for the resistive element into the equivalent value of the desired physical parameter being measured by the resistive element sensor.

17. A method using a universal microcomputer circuit according to claim 7 which comprises the steps of:

charging a capacitor connected in series through a variable resistive element sensor;

accumulating a numerical count proportional to the elapsed time during the charging step;

monitoring the voltage at a point located between the variable resistive element and the capacitor, said monitored voltage being fed to a second input terminal of a comparator;

feeding a preset reference voltage to the first input of the comparator;

comparing the two input voltages with said comparator;

stopping the accumulating numerical count when the compared voltages are equal, whereby said count represents the time to charge the resistance-capacitance circuit to the reference voltage level which in turn is dependent upon the variable value of the resistive sensor;

storing the accumulated count for later processing;

charging the capacitor through a first fixed value resistor which has a resistance value set to represent the upper limit of the dynamic range to be monitored by the variable resistive element sensor;

accumulating a numerical count proportional to the elapsed time during the previous charging step;

monitoring the voltage at a point located between the first fixed value resistor and the capacitor, said monitored voltage being fed to a second input terminal of said comparator;

comparing the monitored voltage of the previous step with the preset reference voltage fed to the first input of the comparator;

stopping the accumulating numerical count when the compared voltages are equal, whereby said count represents the time to charge the resistance-capacitance circuit to the reference voltage level which in turn is dependent upon the value of the first fixed resistor;

storing the accumulated count corresponding to the first fixed resistor;

charging the capacitor through a second fixed value resistor which has a resistance value set to represent the lower limit of the dynamic range to be monitored by the variable resistive element sensor;

accumulating a numerical count proportional to the elapsed time during the previous charging step;

monitoring the voltage at a point between the second fixed resistor and the capacitor, said monitored voltage being fed to a second input terminal of said comparator;

comparing the monitored voltage of the previous step with the preset reference voltage which is fed to the first input of the comparator;

stopping the accumulating numerical count when the compared voltages are equal, whereby said count represents the time to charge the resistance-capacitance circuit to the reference voltage level which in turn is dependent upon the value of the second fixed resistor;

storing the accumulated count corresponding to the second fixed resistor;

computing the value of (the stored count representing the second fixed resistor minus the stored count representing the variable resistive element sensor) divided by (the stored count representing the second fixed resistor minus the stored count representing the first fixed resistor), whereby the answer given is a measurement value of the variable resistive element sensor as a fraction of the dynamic range defined by the first resistor and the second fixed resistors; and

converting this fractional measurement into the desired value of the physical parameter being measured by the variable resistive element sensor.

18. A method using a universal microcomputer circuit according to claim 8 which comprises the steps of:

charging a capacitor by applying a positive voltage to its first side and a negative potential to its second side;

establishing the circuit configuration including the capacitor charged in the first step, said configuration comprising;

a first fixed value resistor connected to the positively charged side of the capacitor, said first fixed value resistor having a resistance value set to represent the upper limit of the dynamic range for the measurement to be taken;

a second fixed value resistor connected to the negative side of the charged capacitor, said second fixed value resistor having a resistance value set to represent the lower limit of the dynamic range for the measurements to be taken;

a comparator connected with its first voltage input attached to a point between the positive side of the charged capacitor and the first fixed value resistor, and its second voltage input connected between the negative side of the charged capacitor and the second fixed value resistor;

a first counter connected to the output of the comparator, said first counter to accumulate numerical count representing elapsed time of discharge of the presently charged capacitor;

applying a positive voltage at the end of the second fixed value resistor which is opposite to that resistor'"'"'s end attached to the charged capacitor, and applying a negative voltage at the end of the first fixed value resistor which is opposite that resistor'"'"'s end attached to the charged capacitor;

starting said first counter to accumulate count simultaneously with the initiation of the voltage difference across the resistance-capacitance circuit in the prior step;

comparing the voltage inputs to the comparator until each voltage input become equal during the period that the capacitor is discharging;

stopping the accumulating count in the first counter when the voltage inputs to the comparator are equal;

storing this accumulated count for later processing;

repeating the above steps with the exception that the second fixed resistor is replaced with a variable resistive element sensor, said variable resistive element sensor monitoring the physical variable of interest in the measurement, and with the further exception that the second accumulated count is recorded and stored in a second counter;

dividing the stored accumulated count from the second counter by the stored accumulated count from the first counter; and

converting the ratio of the divided accumulated counts into the desired value of the physical parameter being measured by the variable resistive element.

19. A method using a universal microcomputer circuit according to claim 9 wherein the output voltage of a full bridge sensor may be monitored, said method comprising the steps:

charging a capacitor which is connected across the input voltage terminals from the full bridge sensor, said capacitor being charged from a power source controlled by the universal microcomputer circuit in a manner that its positive side is connected with the negative input from the full bridge sensor and its negative side is connected with the positive input from the full bridge sensor, and said capacitor being insulated from the voltage input of the full bridge sensor during the charging of said capacitor;

monitoring the voltage difference across the capacitor by a comparator such that one voltage input to the comparator is connected to one side of the capacitor while the second voltage to the comparator is connected to the opposite side of said capacitor;

exposing the charged capacitor to the voltages being input from the full bridge sensor in a manner that the positive side of the full bridge sensor voltage feeds to the negatively charged side of the capacitor and the negative voltage input from the full bridge sensor feeds to the positively charged side of the capacitor;

starting a count accumulating simultaneously with the exposing of the capacitor to the full bridge sensor voltages;

monitoring the voltage across the capacitor with the comparator simultaneously with the accumulating count;

stopping the accumulating count when the voltages monitored by the comparator inputs are equal;

storing the accumulated count for further processing; and

converting the accumulated count into the desired physical parameter being measured by the full bridge sensor.

20. A method using a universal microcomputer circuit according to claim 10 wherein a voltage output from a half bridge sensor is to be monitored, said method comprising the steps:

applying the positive voltage output of the half bridge sensor through a preselected fixed resistor to one side of a capacitor, said capacitor having its other side set at ground potential;

starting a count accumulating simultaneously with exposing of the capacitor to the half bridge voltage output;

monitoring the voltage at a terminal located between said fixed resistor and the high side of said capacitor, said monitored voltage being fed to a first input terminal of a comparator;

feeding a preset reference voltage into the second input of the comparator;

comparing the two input voltages with the comparator;

stopping the accumulating count when the voltages are equal, whereby said count represents the time to charge the resistance-capacitance circuit to the reference voltage level which in turn is dependent upon the voltage output of the half bridge sensor;

processing the accumulated count to obtain the value of the voltage output of the half bridge sensor; and

converting the value of the voltage of the half bridge sensor into the value of the desired physical quantity being measured by the half bridge sensor.