Auber SYL-2342 Manual de instruções - Página 4

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AUBER INSTRUMENTS

The things you should know about alarm

1) Absolute alarm and deviation alarm

High (or low) limit absolute alarm is set by the specific temperatures that the

alarm will be on. Deviation high (or low) alarm is set by how many degrees

above (or below) the control target temperature (SV) that the alarm will be on.

e.g. Assuming ALM1=1000 ºF, Hy-1=5 ºF, SV=700 ºF. When the probe

temperature (PV) is above 705, the deviation alarm will be on. When the

temperature is above 1000 ºF, the process high alarm will be on. Later, when

SV changes to 600 ºF, the deviation alarm will be changed to 605 but process

high alarm will remain the same. Here the Hysteresis Band (Hy) setting is

ignored. Please see 4.5.2 for details.

2) Alarm Suppression feature

Sometimes, user may not want the low alarm to be turned on when starting

the controller at a temperature below the low alarm setting. The Alarm

Suppression feature will suppress the alarm from turning on when the

controller is powered up (or SV changes). The alarms can only be activated

after the PV has reached SV.

This feature is controlled by the B constant of the COOL parameter (see 4.14).

The default setting is alarm suppression on. If you use the AL1 or AL2 relay for

a control application that needs it to be active as soon as the controller is

powered up, you need to turn off the alarm suppression by setting B=0.

3) Assignment of the relays for the alarms

AL1 and AL2 are the name of the two relays used for alarm output. AL1 is the

alarm relay 1 and AL2 is alarm relay 2. Please do not confuse the relays with

alarm parameter ALM1 (process high alarm) and ALM2 (process low alarm).

Either the AL1 or the AL2 can be used for any of the four alarms. AL-P (alarm

output definition) is a parameter that allows you to select the relay(s) to be

activated when the alarm set condition is met.

You can set all four alarms to activate the one relay (AL1 or AL2), but you

can't activate both relays for with just one alarm.

4) Display of the alarm

When AL1 or AL2 relay is activated, the LED on the upper left will light up. If

you have multiple alarms assigned to a single relay, you might want to know

which alarm activated the relay. This can be done by setting the E constant in

the AL-P parameter (see 4.13). When E=0, the bottom display of the controller

will alternately display the SV and the activated alarm parameter.

5) Activate the AL1 and AL2 by time instead of temperature

For the controllers with the ramp and soak function (SYL-2342P and SYL-

2352P), AL1 and AL2 can be activated when the process reaches a specific

time. This is discussed in the section 3.7 of "Supplementary Instruction Manual

for ramp/soak option.

4.4.2 Hysteresis Band "Hy"

The Hysteresis Band parameter Hy is also referred as Dead Band, or

Differential. It permits protection of the on/off control from high switching

frequency caused by process input fluctuation. Hysteresis Band parameter is

used for on/off control, 4-alarm control as well as the on/off control at auto

tuning. For example: 1) When controller is set for on/off heating control mode,

the output will turn off when temperature goes above SV+Hy and on again

when it drops to below SV-Hy. 2) If the high alarm is set at 800 °F and

hysteresis is set for 2 °F, the high alarm will be on at 802 °F (ALM1+Hy) and

off at 798 °F (ALM1-Hy).

Please note that the cycle time can also affect the action. If the temperature

passes the Hy set point right after the start of a cycle, the controller will not

respond to the Hy set point until the next cycle. If cycle time is set to 20

seconds, the action can be delay as long as 20 seconds. Users can reduce

the cycle time to avoid the delay.

4.4.3 Control mode "At"

At=0 On/off control. It works like a mechanical thermostat. It is suitable for

devices that do not like to be switched at high frequency, such as motor and

valves. See 4.5.2 for details.

At=1 Gets the controller ready to start the Auto tuning process by pressing the

A/M key.

At=2 Start auto tuning. The function is the same as starting auto tuning from

front panel.

At=3 This configuration is automatically set after auto tuning is done. Auto

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tuning from the front panel is inhibited to prevent accidental re-starting of the

auto tuning process. To start auto tuning again, set At=1 or At=2.

4.5 Control action explanations

4.5.1 PID

Please note that because this controller uses fuzzy logic enhanced PID

control software, the definition of the control constants (P, I and d) are

different than that of the traditional proportional, integral, and derivative

parameters.

In most cases the fuzzy logic enhanced PID control is very adaptive and may

work well without changing the initial PID parameters. If not, users may need

to use auto-tune function to let the controller determine the parameters

automatically. If the auto tuning results are not satisfactory, you can manually

fine-tune the PID constants for improved performance. Or you can try to

modify the initial PID values and perform auto tune again. Sometimes the

controller will get the better parameters.

The auto-tune can be started in two ways. 1) Set At=2. It will start

automatically after 10 seconds. 2) Set At=1. Then you can start the auto-tune

any time during the normal operation by pressing the A/M key. During auto

tuning, the instrument executes on-off control. After 2-3 times on-off action,

the microprocessor in the instrument will analyze the period, amplitude,

waveform of the oscillation generated by the on-off control, and calculate the

optimal control parameter value. The instrument begins to perform accurate

artificial intelligence control after auto tuning is finished. If you want to exit

from auto tuning mode, press and hold the (A/M) key for about 2 seconds

until the blinking of "At" symbol is stopped in the lower display window.

Generally, you will only need perform auto tuning once. After the auto tuning

is finished. The instrument will set parameter "At" to 3, which will prevent the

(A/M) key from triggering auto-tune. This will prevent an accidental repeat of

the auto-tuning process.

(1) Proportional constant "P"

Please note the P constant is not defined as Proportional Band as in the

traditional model. Its unit is not in degrees. A larger constant results in larger

and quicker action, which is the opposite of the traditional proportional band

value. It also functions in the entire control range rather than a limited band.

If you are controlling a very fast response system (>1 °F/second) that fuzzy

logic is not quick enough to adjust, set P=1 will change the controller to the

traditional PID system with a moderate gain for the P.

(2) Integral time "I"

Integral action is used to eliminate offset. Larger values lead to slower action.

Increase the integral time when temperature fluctuates regularly (system

oscillating). Decrease it if the controller is taking too long to eliminate the

temperature offset. When I =0, the system becomes a PD controller.

(3) Derivative time "D"

Derivative action can be used to minimize the temperature over-shoot by

responding to its rate of change. The larger the number, the faster the action.

4.5.2 On/off control mode

It is necessary for inductive loads such as motors, compressors, or solenoid

valves that do not like to take pulsed power. It works like a mechanical

thermostat. When the temperature passes the set point, the heater (or

cooler) will be turned off. When the temperature drops back to below the

hysteresis band (Hy) the heater will turn on again.

To use the On/off mode, set At=0. Then, set the Hy to the desired range

based on control precision requirements. Smaller Hy values result in tighter

temperature control, but also cause the on/off action to occur more

frequently.

103

SV+Hy

100

SV-Hy

Relay On

Figure 5. On/off control mode

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When heating, At=0

If PV≤(SV-Hy), relay on

If PV≥(SV+Hy), relay off

(SV=100, Hy=3)

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