the time interval between each measurement t sub int the maximum time laps for detecting the presence of an occlusion t sub exp the trigger level of temperature difference between t 1 and t 2 t sub diff and the constant for the calculating the instant flow rate c sub q in embodiments where the flow cell 200 is predisposed with more temperature measurement locations along its fluid channel additional permutations of t sub diff could be developed to further improve the accuracy of flow rate determination when the measurement cycle starts step 423 the thermal source 109 will be turned on and off intermittently to emit heat pulses to the fluid in the channel 213 in one embodiment the thermal source 109 turns on for the duration of t sub iron then turns off the temperature difference t sub diff between the readings at thermal sensors 110 t 2 and 111 t 1 is measured and a timer starts to count time interval t sub int for the start of the next measurement cycle step 424 which helps to ensure that the measurements are taken at equal intervals at step 425 the measured temperature difference t 2 u2212 t 1 is compared against a predetermined trigger level t sub diff to confirm the existence of fluid flow versus occlusion in other words the mcu 130 checks whether the temperature difference between t 1 and t 2 exceeds the trigger level t sub diff if there is occlusion the difference in the temperature readings taken by thermal sensors 110 and 111 will.