Watlow Series 988 - Manual (Page 150)

WATLOW Series 988 User’s Manual 9.13 Enhanced Software Features, Chapter 9
Enhanced Software
Sample Application
Blue pigment must be added to paint at a ratio of one part per 100 to cre-
ate a mixed paint of the desired color. The uncolored paint flows into the
mixer in an uncontrolled stream that is set manually and sensed by input
2. A motorized valve controls the flow of pigment, which is monitored by
the flow sensor to input 1. The flow rate of the uncolored paint determines
the set point for the motorized valve that controls the pigment flow. If an
operator needs to change the rate of flow for the uncolored paint, the set
point will shift accordingly to maintain the correct ratio in the mixing
tank.
The application engineer set up this feature in software by choosing ratio
[rAti] as the control [CntL] parameter in the Global Menu. The set point
value displayed was then a ratio value. He entered 0.01 to maintain an
input 1:input 2 ratio of 1:100.
TL TL W W W WA A
PROCESS
L1 L2 L3 L4
DEV
% OUT DISPLAY
MODE
AUTO
MAN
SERIES 988
input 1
input 2
output 1
controlled flow
of pigment flow
transmitter
motorized
valve
Mix ing Ta nk
flow
transmitter
mixed paint
uncontrolled
flow of
unmixed paint
Figure 9.13 - Mixing
tank with ratio con-
trol.