Hybrid Constant Temperature Regulator

Abstract

A powerful temperature difference measuring relation method using the high resistance ratio-metric sensors which is improving the accuracy, because it can solve such problems as dependence of a sensor's sensitivity to such factors as power supply instability, ambient temperature, humidity, pressure, effects of self-heating, aging, etc. was presented in [ezni ek et al, 2001]. Many similar derivate relation ratio measuring and monitoring systems were developed for biosensor applications etc. presented in (Tvarozek et al., 2002), (Vavrinsky et al., 2003), and for micro-calorimetric applications (ezni ek and Szendiuch, 2005), (ezni ek et al., 2005) to time. The combination of these methods was studied for many applications in continual process constant temperature controlling. The process energy is balanced at defined constant temperature with the highest sensitivity and the lowest time-current delay using the special balance sensor consisted of electronic energy balance switching circuit with operational amplifier. The sensor heater contains of two asymmetric low resistance dividers in anti-parallel circuit wired to output of power linear operational amplifier: two of unequal resistors (Pt1 and Pt2) are temperature-dependent (Pt) and second couple of unequal resistors (R1 and R2) are temperature non-dependent (NiCr or AgPd). The sensor heater contains of four resistors ceramic substrate on realized, two of them (Pt1 and Pt2) are temperature-dependent (Pt) and second one (R1 and R2) are temperature non-dependent (NiCr or AgPd) resistors. The coefficient of asymmetry defined how resistance ratio K=Ptl/(Ptl+Pt2) is equal to R1/(R1+R2) and must be different of frac12. It means that the resistances of resistors Pt1 and Pt2 or R1 and R2 can't be the same. The temperature sensitivity VTCR of heater is defined by formula VTCR = -(2K-l)*TCR/4 and it is calibrate-able by trimming of coefficient K. Itself balance heater working temperature is defined by value of resistance R1 or R2 in relation to resistance of Pt1 or Pt2. The itself balance heater temperature is defined by equality R1=Pt1 or R2=Pt2 by relation Ty = (R1-Pt10)/TCR*Pt10, where the Pt10 is resistance of resistor Pt1 by temperature 0degC. This is first one of designed heater parameters. Second one is the current limit determined by the maximal heater output and the system power voltage by implication. Finally third one is heater temperature sensitivity defined hereinbefore