Boundless ADDS 6700 Manual download pdf (Page 142)

-DIN,

-DIN &

- DIN Controllers & Indicators - Product Manual

59305, Issue 7 – March 2014 Glossary Page 137

Bias (Manual Reset) Type: Controller Tuning Parameter

Used to manually bias the proportional output(s) to compensate for process load variations.

Bias is expressed as a percentage of output power and is adjustable in the range 0% to

100% (for Primary Output alone) or -100% to +100% (for both Primary and Secondary

Outputs). This parameter is not applicable if the Primary output is set to ON/OFF control

mode. If the process settles below setpoint use a higher Bias value to remove the error, if the

process variable settles above the setpoint use a lower Bias value. Lower Bias values will

also help to reduce overshoot at process start up.

Display code = , default value = 25%.

Also refer to ON/OFF Control and PID.

Bumpless Transfer Type: Controller Definition

A method used prevent sudden changes to the output power level when switching between

Automatic and Manual control modes. During a transition from Automatic to Manual, the

initial Manual Power value will be set to equal the previous automatic mode value. The

operator can then adjust the value as required. During a transition from Manual to Automatic,

the initial Automatic Power value will be set to equal the previous manual mode value. The

correct power level will gradually applied by the control algorithm at a rate dependant on the

integral action resulting from the Automatic Reset time. Since integral action is essential to

Bumpless Transfer, this feature is not available if Automatic Reset is turned off.

Also refer to Automatic Rest and Manual Mode

Boundless VMD Control Type: VMD Controller Definition

- Refer to Open Loop VMD.

Cascade Control Type: Controller Definition

Applications with two or more capacities (such as heated jackets) are inherently difficult for a

single instrument to control, due to large overshoots and unacceptable lags. The solution is

to cascade two or more controllers, each with its own input, in series forming a single

regulating device. The product setpoint temperature is set on the master controller. This is

compared to the product temperature, and the master’s PID output (mA or VDC) is fed into a

remote setpoint input on the slave. The RSP is scaled to suit any expected temperature. The

slave loop’s natural response time should ideally be at least 5 times faster than the master.

In the example, the maximum input represents 400ºC, thus restricting the jacket temperature.

At start-up the master compares the product temperature (ambient) to its setpoint (300ºC)

and gives maximum output. This sets the maximum (400ºC) setpoint on the slave, which is

compared to the jacket temperature (ambient) giving maximum heater output.

As the jacket temperature rises, the slave’s

heater output falls. The product

temperature also rises at a rate dependant

on the transfer lag between the jacket and

product. This causes the master’s PID

output to decrease, reducing the ‘jacket’

setpoint on the slave, effectively reducing

the output to the heater. This continues

until the system becomes balanced.

1 2 ... 137 138 139 140 141 142 143 144 145 146 147 ... 176 177

Comments to this Manuals

No comments

Boundless ADDS 6700 Manual Page 142

Comments to this Manuals