Another way of a liquid flow measurements by using a specially designed turbine
Način merenja pretoka tekočin s posebno turbino

english

2000

volume 30, issue 3

Biomedical engineering   Blood flow velocity   Cardiac output   Instrumentation   Methods   Swine

Strokovno društvo za mikroelektroniko, elektronske sestavne dele in materiale

We designed a special measuring turbine which is suitable for measurements of flow of various liquids in laboratory and animal experiments in medicine. Specifically, the turbine was designed for measurements of blood flow in isolated working pig hearts. The basic principle of measuring of liquid flow through the turbine is based on measurement of the time elapses when the rotorrotates by one degree. For this purpose, the rotor is equiped with circular and transparent foil having a ring of 360 black lines printed near the circumference of the foil and oriented towards its centre. Sensory part isrealized using two infra-red light-emitting diodes mounted on one side of the foil and two photo transistors as sensors of the tramsitted infra-red light mounted on the other. By this way, the direction of rotation of the rotor can be identified. The characteristics of electronic part of the turbineare as follows: voltage regulated output, ranging from 0 to +- 2.048 V,factor of a transformation described as 1 revolution of a rotor/s = 500 mV at the output (changeable by the programme), calculating time is 2 ms and resolution is 1 mV (11bits). The electronic part is powered by external power supply of 5V. The turbine showed a linear response at a continuous saline flowup to 3,000 ml min-1 at pressure loads of between 20 and 220 cm H2O. Pressure drop across the turbine depends on the volume flow and was 1 mmHg at100 ml min-1 and 5mmHg at 7,000 ml min-1. A rotating moment 1.25x10-4 kg m2 s-1 was calculated. The lowest volume change of a bolus of saline solution, detected by the turbine, was 1.6 ml. Similar, suitable adapted turbine could be used also for measurments of much bigger liquid flows.

18.12.2015