Apparatus for producing an electrical output signal whose magnitude is linearly representative of the value of an unknown resistance

Apparatus for producing an electrical output signal whose magnitude is linearly representative of an unknown electrical conductance, the apparatus comprising:

• means for applying a voltage to the unknown conductance to pass therethrough an analogue current whose magnitude is dependent on the value of the unknown conductance;
• integrating means;
• first circuit means for applying the analogue current to the integrating means during a first time interval so as to drive the level of the signal at the output of the integrating means away from a datum value;
• a source of a reference signal;
• second circuit means for applying the reference signal to the integrating means during a second time interval which succeeds the first time interval, so as to drive the level of the signal at the output of the intergrating means back towards the datum value;
• and
• means responsive to the level of the signal at the output of the integrating means for producing an output signal whose magnitude is representative of the ratio between the respective durations of said first and second time intervals;
• third circuit means for applying a predetermined multiple of the analogue current to the integrating means during the second time interval;
• the magnitude of said predetermined multiple of the analogue current being selected to ensure that said ratio is linearly related to the value of the unknown conductance, whereby the magnitude of said output signal is linearly representative of the value of the unknown conductance.

Apparatus for producing an electrical output signal whose magnitude is linearly representative of the value of an unknown electrical resistance, the apparatus comprising:

• means for passing a current through the unknown resistance to generate an analogue voltage thereacross whose magnitude is dependent on the value of the unknown resistance;
• integrating means;
• first circuit means for applying the analogue voltage to the integrating means during a first time interval, so as to drive the level of the signal at the output of the integrating means away from a datum value;
• a source of a reference signal;
• second circuit means for applying the reference signal to the integrating means during a second time interval which is included within the first time interval so as to drive the level of the signal at the output of the integrating means back towards the datum value;
• and
• means responsive to the level of the signal at the output of the integrating means for producing an output signal whose magnitude is representative of the ratio between the respective durations of said first and second time intervals;
• third circuit means for applying a predetermined multiple of the analogue voltage to the intergrating means during the second time interval, in addition to the application of the analogue voltage already taking place via the first circuit means;
• the magnitude of said predetermined multiple of the analogue voltage being selected to ensure that said ratio is linearly related to the value of the unknown resistance, whereby the magnitude of said output signal is linearly representative of the value of the unknown resistance.

Apparatus for producing an electrical output signal whose magnitude is linearly representative of an unknown electrical conductance, the apparatus comprising:

• means for applying a voltage to the unknown conductance to pass therethrough an analogue current whose magnitude is dependent on the value of the unknown conductance;
• integrating means;
• first circuit means for applying the analogue current to the integrating means during a first time interval so as to drive the level of the signal at the output of the integrating means away from a datum value;
• a source of a reference signal;
• second circuit means for applying the reference signal to the integrating means during a second time interval which is included within the first time interval, so as to drive the level of the signal at the output of the integrating means back towards the datum value;
• and
• means responsive to the level of the signal at the output of the integrating means for producing an output signal whose magnitude is representative of the ratio between the respective durations of said first and second time intervals;
• third circuit means for applying a predetermined multiple of the analogue current to the integrating means during the second time interval, in addition to the application of the analogue current already taking place via the first circuit means;
• the magnitude of said predetermined multiple of the analogue current being selected to ensure that said ratio in linearly related to the value of the unknown conductance, whereby the magnitude of said output signal is linearly representative of the value of the unknown conductance.

In an apparatus for producing an electrical output signal whose magnitude is linearly representative of the value of an unknown electrical resistance, the apparatus including:

• means for passing a current through the unknown resistance to generate an analogue voltage thereacross whose magnitude is dependent on the value of the unknown resistance;
• integrating means;
• first circuit means for applying the analogue voltage to the integrating means during a first time interval, so as to drive the level of the signal at the output of the integrating means away from a datum value;
• a source of a reference signal;
• second circuit means for applying the reference signal to the integrating means during a second time interval, so as to drive the level of the signal at the output of the integrating means back towards the datum value;
• and means responsive to the level of the signal at the output of the integrating means for producing an output signal whose magnitude is representative of the ratio between the respective durations of the first and second time intervals;
• an improvement for compensating for non-linearity resulting from loading of said analogue voltage by the first circuit means, comprising:
• third circuit means for applying a predetermined multiple of the analogue voltage to the integrating means during the second time interval;
• the magnitude of said predetermined multiple of the analogue voltage being selected such that said ratio is linearly related to the value of the unknown resistance, whereby the magnitude of said output signal is linearly representative of the value of the unknown resistance.

In an apparatus for producing an electrical output signal whose magnitude is linearly representative of an unknown electrical conductance, the apparatus including:

• means for applying a voltage to the unknown conductance to pass therethrough an analogue current whose magnitude is dependent on the value of the unknown conductance;
• integrating means;
• first circuit means for applying the analogue current to the integrating means during a first time interval so as to drive the level of the signal at the output of the integrating means away from a datum value;
• a source of a reference signal;
• second circuit means for applying the reference signal to the integrating means during a second time interval so as to drive the level of the signal at the output of the integrating means back towards the datum value;
• and means responsive to the level of the signal at the output of the integrating means for producing an output signal whose magnitude is representative of the ratio between the respective durations of said first and second time intervals;
• an improvement for compensating for non-linearity resulting from modification of said analogue current by the first circuit means, comprising:
• third circuit means for applying a predetermined multiple of the analogue current to the integrating means during the second time interval;
• the magnitude of said predetermined multiple of the analogue current being selected such that said ratio is linearly related to the value of the unknown conductance, whereby the magnitude of said output signal is linearly representative of the value of the unknown conductance.