Calorimetric. Calorimetric transducers measure the heat
of a biochemical reaction at the sensing element. These
devices can be classified according to the way heat is
transferred. Isothermal calorimeters maintain the reaction
cell at constant temperature using Joule heating or Peltier
cooling and the amount of energy required is measured.
Heat conduction calorimeters measure the temperature
difference between the reaction vessel and an isothermal
heat sink surrounding it. Using highly conducting
materials ensure quick heat transferred between the
reaction cell and the heat sink. Finally, the most commonly
used is the isoperibol calorimeter that also measures the
temperature difference between the reaction cell and an
isothermal jacket surrounding it. However, in this case the
reaction cell is thermally insulated (adiabatic). This
calorimeter has the advantage of being easily coupled to
flow injection analysis systems[29] [see Fig. 1(d)].