Test Two Flashcards
What is open loop control?
Cheaper to install
Usually no feedback signal
Typically requires an operator
Usually not automatic
What is closed loop control?
Will have feedback signal
Can be automatic
Has measurement devices or sensors
Can run 24/7
Has a PLC or some type of controller
What is process control?
The set point remain unchanged
Objective of the system is to maintain set-point at all times
Example is batch process- making cookies
What is motion control?
Also referred to as servo control
Uses PID block
setpoint changes frequently
What are function blocks?
Programing blocks that will perform a predetermined function
What does the equal function block do?
Source A is equal to source B. The block will go high for one scan
What does the greater function block do?
When source A is greater than source B it will send a high signal for one scan
What does the less than function block do?
When source A is less than source B it will send a high signal for multiple scans
What is Level Control?
The height at which a container is filled with a material
What is point to point level control?
Typically have two sensors. One at the low point and one at the high point
What is continuous level control?
Always monitoring one set point at all times
What should one considered when selecting a measurement device?
What is the material being measured?
What is the cost of the sensor?
How accurate does it have to be?
What are direct level measurement types?
A float or sight glass
Typically mechanical
What is a mechanical measurement device?
A paddle wheel or other types of displacement methods
What are electronic or indirect measurement devices?
Conductive probes
Radar level detector
D.P Cell
All sensors with a transmitter or transducer
What are power sources in level control?
A pump or auger to move material
Static pressure tank
What are transfer systems in level control?
Pipes and conveyors
What was used in the lab to create this automatic on/off level controller?
Two function blocks. One less than and one greater than. Feedback signal from the D.P cell
What sensor is used for the automatic on/off level controller?
D.P Sensor
What is the tag of the sensor in the program?
DP level to PV
How does this sensor work?
Using pressure of the water in the tank to convert it to a 4-20 mili amp signal
What function blocks were used in the automatic on/off level control?
Greater than and less than
On/Off control with point or continuous level indication?
Point level control system
Created with two set points
How was the start command built into the HMI program? What was used?
A less than function block. Internal control relay and a N.O contact in parallel
