he controlling software was written in C and took advantage of the National
Instruments API to control the system through the PCI-6601 DAQ/IO card. It
is an autonomous executable which provides a text-based user interface and high
level system control.
All measurements are made as per Interface
Level Measurement section. The software makes one measurement
without Cx in the circuit, then activates an analog switch to include Cx and
makes another measurement. After mathematical manipulation, and reference
to a lookup table, an interface level is determined. If the interface has
just been moved, the software will make several of these measurements until it
is satisfied that all settling has finished before reporting the value.
The software performs the following functions:
||Reports current interface
||Reports percent height to screen.
||Allows manual raising or
lowering of the interface
||Gives the user control over the pump or valve,
||Provides automated level
setting for the interface
||This is a more complicated procedure.
The user enters a desired interface level, which is then compared
against a measured level to determine the direction the interface must
move. Levels may be specified between 5% and 95 % of the height of
Due to the physical limitations of the system, and in the interest of
scalability to allow an indeterminate number of Flo.Point devices to be
connected, it is not possible to move the interface to the desired level
in one step. Rather, the program takes an iterative approach,
stepping in the correct direction, measuring to determine the new
interface level, and repeating.