Image Number 3 for United States Patent #8092084.
A method for precision thermal measurement and control, especially for bioreactors, as well as the correction of temperature sensitive probes such as pH and dissolved oxygen. Typical control requirements are +/-0.1.degree. C. The thermal measurement circuit converts a sensor output to a high level voltage or current with great accuracy and provides noise immunity and sensor isolation. While digital outputs from sensor converters can have the greatest noise immunity, the noise associated with digital circuitry may contaminate low level sensor signals so in many cases an analog sensor converter is preferred because of low noise generation, especially if the converter is near the sensor. The circuit is low cost, reliable, generates minimal heat is immune to, and does not generate noise, and requires minimal calibration effort.