Experimental results on dynamic behavior of thermistor flowmeters

The influence of nonlinear effects on the dynamic behavior of self-heated thermistor flowmeters is studied. The nonlinear equation which describes the device thermal balance is solved by numerical methods and the theoretical previsions are compared with the results of experimental measurements. The results emphasize that a description of dynamic behavior of thermistor flowmeters by means of one time constant is very unsatisfactory. Either response time or sensitivity can be changed appreciably by changing the bias conditions of the self-heated thermistor and a criterion is suggested for the choice of bias conditions which provide the best response speed and sensitivity of the system.