N+1 bit resolution from an N bit A/D converter

A method of generating an N+1 bit resolution from an N bit A/D converter comprising the steps of:

• generating a conversion signal from a microprocessor to initiate the conversion of an analog signal to a digital word by the A/D converter;
• generating a first N bit digital word from the analog signal in the A/D converter;
• generating a control signal from the microprocessor indicating that an N+1 bit digital word resolution is to be generated;
• responding to said control signal to generate an electrical signal according to the following formula
• V.sub."dither" =(V+)/2.sup.(N+1)
• where N=the number of bits of normal resolution of the A/D converter;
• where V+=the high voltage reference to the A/D converter
• applying said electrical signal to the A/D converter to shift the input range of the analog signal;
• generating a second N bit digital word from the analog signal in the A/D converter;
• and then
• summing the first and second N bit digital words in the microprocessor to get an N+1 bit digital word wherein the least significant bit position resolution has been increased.

A system for generating an N+1 bit resolution from an N bit A/D converter, said system comprising:

• control means for generating a control signal;
• a logic circuit means including a resistance circuit means having a plurality of resistances of either of two values, said resistance circuit for supplying two different voltages and responsive to said control signal for generating two offset symetrical voltages to be added to said two different voltages;
• an A/D converter adapted to receive said two different voltages for identifying the range of the analog signal to be converted into a first digital word of N bits and in response to said control signal to receive said two offset symetrical voltages added to said two different voltages for identifying the second range of the analog signal to be converted into a second digital word of N bits;
• and
• a microprocessor means responsive to said A/D converter signals for summing said first and second digital words into an N+1 digital word wherein the least significant bit position resolution has been increased.