Sensor data input by means of analog to pulse width-to digital converter

In combination with a digital processing system having at least two sensors disposed at remote locations generating analog signals in response to sensed inputs and a digital processor for generating output signals in response to digital input signals, said digital processor means further including means for generating interrogation signals indicative of a transition from a second signal level to a first signal level substantially different from said second signal level, an improved analog to digital data conversion and data transmission network comprising:

• first pulse width generating means disposed at one of said remote locations and enabled by each of said interrogation signals for integrating the analog signals generated by one of said at least two sensors to generate a first pulse width signal having a pulse width equal to the time required for the integrated value of the received analog signals to reach a predetermined value, said first pulse width signal formed by a transition from said same second signal level to said same first signal level;
• second pulse width generator means disposed at the other of said remote locations and enabled by said interrogation signals for integrating the analog signals generated by said other sensor to generate a predetermined time after the occurrence of each of said interrogation signals, a second pulse width signal having a pulse width equal to the time required for the integrated value of the received analog signals to reach a predetermined value, said second pulse width signals formed by a transition from said same second signal level to said same first signal level;
• digital data generator means interfacing said digital processor and receiving said pulse width signals from said first and second pulse width generator means and said interrogation signals for generating said digital data, said digital data indicative of the pulse width of said pulse width signals;
• and
• a single bi-directional data transmission line for transmitting said interrogation and pulse width signals between said first and second pulse width generator means and said digital data generator means;
• wherein said first and second pulse width generator means each comprises:
• bi-stable means switchable between two stable states for switching to a first state and generating a first signal having a signal level the same as said first signal level in response to said interrogation signals and for switching to a second state and generating a second signal having a signal level the same as said second signal level in response to a reset signal, wherein said first signal is said pulse width signal;
• means enabled by said first signal and disabled by said second signal for integrating the analog signal generated by the sensors to generate an integrated signal having a value proportional to the value of said analog data and the time of integration;
• means enabled by said first signal for generating said reset signal each time said integrated signal exceeds a predetermined value;
• pulse width signal isolation means interfacing said bi-directional data transmission line for isolating said bi-stable means from the pulse width signals on said bi-directional data transmission line for a predetermined interval after said interrogation signal;
• and
• wherein said second pulse width generator means further includes delay means for delaying for said predetermined time the switching of said bi-stable means to said first state in response to said interrogation signals.

An analog-to-pulse width-to-digital converter and data transmission circuit responsive to interrogation signals indicative of a transition between a pair of signal levels which are significantly different comprising:

• first means enabled by each interrogation signal for converting analog signals generated by a first source to pulse width signals said pulse width signals having pulse widths indicative of the value of the received analog signals and formed by a transition between the same pair of signal levels as the interrogation signals;
• at least one second means enabled by each interrogation signal for converting analog signals generated by at least one other source to pulse width signals a predetermined time after receiving said interrogation signal, said pulse width signals having pulse widths indicative of the value of the received analog signals and formed by a transition between the same pair of signal levels as the interrogation signals;
• third means receiving said pulse width signals and said interrogation signals for generating digital data indicative of the pulse width of the pulse width signals generated by said first and said at least one second means;
• and
• a single bi-directional data transmission line for transmitting said interrogation and said pulse width signals between said first, second and third means;
• and
• wherein said first and said at least one second means each comprises:
• bi-stable means switchable between two stable states for switching to a first state and generating a first signal having a signal level the same as one of said pair of signal levels in response to said interrogation signals and for switching to a second state and generating a second signal having a signal level the same as the other of said pair of signal levels in response to a reset signal, wherein said first signal is said pulse width signal;
• means enabled by said first signal and disabled by said second signal for integrating said analog signal to generate an integrated signal having a value proportional to the value of said analog data and the time of integration;
• means enabled by said first signal for generating said reset signal each time said integrated signal exceeds a predetermined value;
• pulse width signal isolation means interfacing said bi-directional data transmission line for isolating said bi-stable means from the pulse width signals generated on said bi-directional data transmission line for a predetermined time after receiving an interrogation signal;
• and
• wherein each of said at least one second means further includes:
• a delay means for delaying for a predetermined period the switching of said bi-stable means to said first state in response to an interrogation signal.

A method for transmitting information from at least two remote sources of analog information to a digital processor and for converting said analog information to digital data comprising the steps of:

• generating on a single bi-directional data transmission line interconnecting said remote sources with said digital processor interrogation signals in the form of a transition between a pair of signal levels which are substantially different;
• enabling in response to each interrogation signal a first converter means in circuit relationship with said single bi-directional data transmission line to integrate the analog information generated by one of said at least two sources and generate a pulse width signal having a pulse width equal to the time required for said integrated analog information to reach a predetermind value, said pulse width signal being a transition between the same pair of signal levels as said interrogation signal;
• enabling in response to each interrogation signal at least one second converter means in circuit relationship with said single bi-directional data transmission line to integrate the analog information generated by the other of said at least two sources and to generate after a predetermined period of time a pulse width signal having a pulse width equal to the time required for said integrated analog information to reach a predetermined value, said pulse width signal being a transition between the same pair of signal levels as said interrogation signal;
• and
• transmitting said pulse width signals to a digital converter means interfacing the digital processor by means of said single bi-directional data transmission line, said pulse width signals activating said digital converter means to generate digital data indicative of the value of said analog information wherein said digital data is transmitted from said converter means to said digital processor;
• wherein said step of enabling said first and second converter means includes the steps of:
• generating an isolation signal for a predetermined isolation time period after the termination of each interrogation signal;
• and
• activating an electronic gate between first and second converter means and said bi-directional transmission line in response to said isolation signal to electrically isolate the input of said first and second converter means from the signals on said bi-directional line for said predetermined isolation time period;
• and
• wherein said step of enabling said second converter means further includes the steps of:
• activating a delay circuit in each of said second converter means in response to the termination of said interrogation signal to delay the generation of pulse width signals generated by successive second converter means for predetermined successively longer periods of time so that the pulse width signals successive generated by said first and said at least one second inverter means generate said pulse width in a sequential order.