Continuously calibrating temperature controller

A method for operating a measurement system including a current source, a sensor and a first calibration device, said method comprising the steps of:

• establishing a plurality of successive cycles of operation of said measurement system;
• during each of said successive cycles of operation, causing said measurement system to perform a measurement operation by coupling said current source to said sensor to cause said sensor to produce a measurement signal representative of a parameter to be measured, and producing an output value of said parameter;
• and
• during at least some of said successive cycles of operation, calibrating said measurement system by coupling said current source to said first calibration device to cause said first calibration device to produce a first calibration value representing a first reference value of said measurement signal.

A multiple-channel temperature measurement system comprising:

• a plurality of temperature inputs adapted to be connected to a corresponding plurality of resistance temperature devices for sensing temperatures at a plurality of locations;
• a current circuit for applying a known current to a selected one of said resistance temperature devices through the corresponding one of said temperature inputs to produce an analog voltage output indicative of a sensed temperature;
• a measurement circuit for converting said analog voltage to a temperature value;
• a first multiplexer circuit connected between said current circuit and said plurality of temperature inputs for selectively connecting said current circuit to individual ones of said resistance temperature devices;
• a second multiplexer circuit connected between said measurement circuit and said plurality of temperature inputs for selectively connecting said measurement circuit to individual ones of said resistance temperature devices;
• and
• a control circuit for controlling said first and second multiplexer circuits to successively connect each of said temperature inputs to said current circuit and simultaneously to said measurement circuit.

A method for performing multiple-channel temperature measurements, comprising the steps of:

• providing a plurality of resistance temperature devices for sensing temperature at a plurality of locations;
• providing a common current circuit for applying a known current to a selected ones of said resistance temperature devices to produce analog voltage outputs indicative of sensed temperatures;
• providing a common measurement circuit for converting said analog voltage outputs to temperature values;
• and
• connecting said common current circuit and said common measurement circuit simultaneously to individual ones of said resistance temperature devices in succession in order to obtain successive temperature values for said plurality of locations.

A measurement system comprising:

• a first input line adapted to be connected to a first sensor for sensing a parameter to be measured and producing an analog output signal representative thereof;
• an analog-to-digital converter for converting an analog output signal from said first sensor to a digital output value, said analog-to-digital converter having an analog input coupled to said first input line, a digital output, and a data ready output;
• and
• a programmable microprocessor coupled to said digital output for processing said digital output value, said microprocessor having an interrupt input coupled to said data ready output of said analog-to-digital converter and being programmed to process said digital output value in response to an interrupt signal on said interrupt input.

A method for operating a measurement system comprising a first sensor, an analog-to-digital converter, and a microprocessor, said method comprising the steps of:

• producing an analog output from said first sensor representing a parameter to be measured;
• coupling said analog output to an analog input of said analog-to-digital converter;
• producing a data ready output from said analog-to-digital converter when digital data is available at a digital output of said analog-to-digital converter;
• triggering an interrupt in said microprocessor in response to said data ready output;
• and
• causing said microprocessor to process said digital data during said interrupt.