Transmitter with vernier measurement

A circuit for providing an output as a function of a sensed parameter, comprising:

• generating means for providing a generator signal which is formed by a plurality of charge packets and which is a function of the sensed parameter, the generating means including reactance means for forming the charge packets;
• measurement means for providing a measurement signal as a function of the generator signal;
• comparator means for providing a comparator output indicating that the measurement signal has passed a first comparator threshold;
• feedback means for providing a feedback signal to the generating means as a function of the comparator output to control the generator means such that the generator signal tends toward a charge-balanced state, the feedback means including means for altering a level of electrical excitation provided to the reactance means to vary sensitivity of the circuit to the sensed parameter;
• and
• output means for providing an output signal as a function of a count of charge packets.

A measurement circuit for providing a measurement output as a function of a sensed parameter, comprising:

• sensing means forming a number of charge packets having a first polarity and a number of charge packets having a second polarity opposite the first polarity, each of such packets comprising a quantity of charge, the quantity of charge in at least some of the packets being a function of the process variable and a level of electrical excitation;
• intgrator means for receiving the charge packets and providing an integrator output representative of the quantities of charge received;
• control means for controlling the numbers of charge packets as a function of the integrator output such that the quantity of charge received by the integrator means is balanced;
• excitation varying means for varying the level of electrical excitation to ary sensitivity of the circuit to the sensed parameter;
• and
• output means for providing an output as a function of the numbers of charge packets formed.

A measurement cirucit for providing a measurement output as a function of a sensed parameter, the circuit comprising:

• means for providing an electrical excitation having a level which varies as a function of a control signal;
• means for forming a plurality of charge packets having a first polarity and a plurality of charge packets having a second polarity opposite the first polarity, each of such packets comprising a quantity of charge, the quantity of charge in at least some of the packets being a function of the sensed parameter and the level of electrical excitation;
• means for receiving the charge packets and providing an integrator output representative of an accumulated quantity of charge;
• means for controlling numbers of charge packets formed as a function of the integrator output such that the accumulated quantity of charge tends to be balanced;
• means for providing the control signal to vary the level of electrical exitation and thereby vary sensitivity of the circuit to the sensed parameter;
• and
• means for providing an output representative of the sensed parameter as a fucntion of numbers of charge packets formed.

A circuit for provding an output signal as a function of a sensed parameter, the circuit comprising:

• reactance means for forming positive and negative charge packets, at least some of the charge packets having a quantity of charge which varies as a function of the sensed parameter;
• means for storing charge from the charge packets;
• means for altering polarity of the charge packets being provided to the means for storing when an amount of charge stored passes a threshold, so that quantities fo positive and negative charge provided to the means for storing tends toward a balanced state;
• means for altering the level of electrical excitation to the reactance means to vary sensitivity of the circuit to the sensed parameter;
• and
• means for providing the output signal based upon a count of charge packets provided to the means for storing.

A circuit for providing an output signal which is a function of a sensed parameter, the circuit comprising:

• means for forming positive and negative charge packets, at least some of the charge packets having a charge whose quantity is representative of the magnitude of the sensed parameter;
• means for storing the charge contained in charge packets its receives;
• means for selecting the charge packets to be provided to the means for storing so that over time no net charge accumulates in te means for storing;
• means for altering a level of electrical excitation to the reactance means to vary sensitivity of the circuit to the sensed parameter;
• means for counting numbers of charge packets provided to the means for storing;
• and
• mens for providing the output signal based upon at least one of the counted numbers of charge packets.

A method of providing an output signal which is a function of a sensed parameter, the method comprising:

• during each of a plurality of measurement cycles:
• forming first charge packets of first polarity having a charge which is a funciton of the sensed parameter and a first excitation level;
• forming second charge packets of sensed opposite polarity having a charge which is a function of the first excitation level;
• selectively transferring the first and second charge packets to a charge accumulator until a charge balance state is passed;
• forming third charge packets of first polarity having a charge which is a function of the sensed parameter and a second, different excitation level;
• forming fourth charge packets of second polarity having a charge which is a function of the second excitation level;
• and
• selectively transferring the third and fourth charge packets to the charge accumulator until the charge balance state is passed;
• counting numbers of first, second, third and fourth charge packets which are transferred to the charge accumulator during a plurality of measurement cycles;
• and
• providing the output signal based on the counted numbers.