The common enthalpiemetric sensor consists of the thermostatic block of at least 10 cm high, which involves input (reference) and output thermistors and a flow cell (Fig. 3.44 a). The common flow rates are about 0.1–2 mL/min and the volume of the enzyme reactor is about 10 mL. Under proper conditions, about 80 % of the evolving heat is converted into the temperature shift measured. For the reaction heat of about 100 kJ/mol, the enzyme conversion of 1 mmol of a substrate yields the increase of the temperature by 0.02 °C. This is quite sufficient for the detection of the rate of the enzymatic reaction because modern thermistors make it possible to detect up to 10−4 oC. The sampling frequency is about 10 measurements per hour (Ramanathan et al. 1998 ).