AJP - Heart and Circulatory Physiology, Vol 248, Issue 2 286-H290, Copyright © 1985 by American Physiological Society
Drop-counting flow computer
C. G. Burgar, G. J. Winter and A. P. Shepherd
An inexpensive microcomputer (VIC-20) was adapted to count drops of fluid
and calculate flow. To minimize both the expense and the bench space
occupied by the flow computer, we eliminated the need for a video monitor
by employing a liquid crystal alphanumeric display. Neither tape recorders
nor disk drives are needed because the flow-computing program resides in a
"game cartridge." Furthermore, the power supply of the computer powers the
interface and display. The computer's real-time clock is utilized to time
intervals between drops falling through an infrared beam. The computed flow
values are then shown on the liquid crystal display, and they are sent to
an external recorder via a digital-to-analog converter. A second
digital-to-analog converter can be used to trigger a fraction collector.
When compared with timed manual collections, the flow computer was shown to
yield highly accurate, linear measurements of water and blood flow.
Although the drops-per-milliliter constant varied with orifice size and
hematocrit, the hematocrit fluctuations observed in typical isolated organ
experiments would not appreciably affect the blood flow determinations.
