Watlow EZ-ZONE PM Integrated Controller - Manual (Page 152)

Watlow EZ-ZONE ® PM Integrated Controller • 149 • Chapter 10 Applications
Example 3: Square Root
Requirements:
One analog input and the enhanced software option are required and at least one output adjusts the controlled
part of the process.
Overview:
Calculates the square root value of the sensor connected to Analog Input 1.
When function is set for Square Root, the PV Function output equals square root value of Source A. Control loop 1
will control Analog Input 1 to Closed Loop Set Point 1.
Example 4: Ratio
Requirements:
Two analog inputs and the enhanced software option are required and at least one output adjusts the controlled
part of the process.
Overview:
The Ratio feature allows control of one process as a ratio of another process. This is especially useful in applica-
tions that mix two materials, whether steam, paint or food ingredients. Analog Input 1 monitors the controlled
part of the process. Analog Input 2 of the controller measures the part of the process that is either uncontrolled or
controlled by another device. The part of the process controlled will be maintained at a level equal to the quantity
measured at input 2 multiplied by the ratio term set by the user as Closed Set Point 1. When function is set for
Ratio, the PV Function output equals Source A as a ratio to Source B. Control loop 1 will control Analog Input 1 to
Closed Loop Set Point 1.
Applications of ratio control:
• Blending two or more flows to produce a mixture with specified composition.
• Blending two or more flows to produce a mixture with specified physical properties.
• Maintaining correct air and fuel mixture to combustion.
Square Root
Closed Loop
Set P
oint
1
Function
Filt
er
Source A
Source A
Heat Power
Cool Power
0 to 100%
0 to 100%
Output
Heat
Cool
Output n
Output n
Analog Input 1
Control Loop 1
PV Function
Ratio
Closed Loop
Set P
oint
1
Function
Filt
er
Source A
Source A
Source B
Heat Power
Cool Power
0 to 100%
0 to 100%
Output
Heat
Cool
Output n
Output n
Analog Input 1
Analog Input 2
Control Loop 1
PV Function
controlled
uncontrolled
controlled flow
of pigment flow
transmitter
motorized
valve
Mixing Tank
flow
transmitter
mixed paint
uncontrolled
flow of
unmixed paint
®
Input 2
Input 1 Output 1