Dwyer SCD User Manual

Page 4

Dual Output Control:

OFF

Set point

Heating

Dead band

Heating hysteresis

Figure 4.

of dual loop output

ON-OFF control

Cooling hysteresis

Cooling

Dead band:dead
band width:positive

Dead band:dead
band width:negative

Output

Heating

Cooling

Set Point

Output

Heating

Cooling

Set Point

Figure 5: PID control,
Dead band is positive

Figure 6: PID control,
Dead band is negative

Description of Function and Parameters Setting:
PID program controlled by 8 patterns (Pattern No. 0 ~ 7) is supported in SCD series. Each pattern contains 8
steps (step No. 0 ~ 7), 1 Link Pattern parameter, 1 Cycle parameter and 1 Actual Step parameter
Start Pattern:

is in operation mode and is used to set the Start Pattern of PID program control (This

parameter appears in

mode only).

Steps: Including set point X and execution time T, the two parameters setting. The set point (SV) should reach
temperature X after the period of execution time T. If the set point is the same as the result of the previous
setting, it is called “Soak” program control. If not, it is called “Ramp” program control. Therefore, PID program
control is also called Ramp/Soak program control.
The default of step No. 0 in this controller is Soak program control. The controller will control the temperature
(PV) and reach the set point X and keep the temperature at set point X. The period of execution time is time T
provided by step No. 0.
Link Pattern Parameter: For example, when

is set as 2, it indicates that pattern No. 2 will be the next to

be executed after the execution of pattern No. 0. If it is set to

, the program will stop after the current pattern

has been executed and the temperature will keep at the set point for the last step.
Cycle Parameter: Additional execution cycle number. For example, when

is set as 2, pattern No. 4

should be executed twice. Including the original one time of execution, the total execution will be three times.
Actual Step Parameter : Number of steps being executed per pattern (can be set as 0 ~ 7). For example, when

is set as 2, pattern No 7 will not execute other steps but step 0 to step2.

Execution: When

is set as

, the program will start to execute in order from step 0 of start pattern.

When

is set as

, the program will stop and the control output will be disabled.

When

is set as

, the program will stop and the temperature at that time will be controlled at the set

point before the program stops. Select

again, and the program will restart and execute from step 0 of start

pattern.
When

is set as

, the program will hold and the temperature at that time will be controlled at the set

point before the program holds. Select

again, and the program will follow the step before hold and start to

execute throughout the rest of the time.

Retransmission Output:
When the 1

group output of this controller is linear voltage or current output, it can be Retransmission that is the

output variation corresponding with input. For example, when read value=0 with input range 0~1000, output will
be 0mA or 0V. When read value=1000, output will be 20mA or 10V.