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AUBER INSTRUMENTS

The things you should know about alarms

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.

For example, ALM1 = 1000 ºF, Hy-1 = 5 ºF, Hy = 1, SV = 700 ºF. When the

probe temperature (PV) is above 706, the deviation alarm will turn on. When

the temperature is above 1001 ºF, the process high alarm will turn on. When

SV changes to 600 ºF, the deviation alarm will be changed to 606 but process

high alarm will remain the same. 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 reaches 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).

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. Please note that

deviation alarm cannot trigger alarm relay AL1. 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, it should be helpful to

know which alarm is activated. 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. This 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 the 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.

2021.06

At = 1. Start auto tuning. In display mode 1, press the A/M key and auto tuning

will initiate.

At = 2. Start auto tuning. It will initiate automatically after 10 seconds. The

function is the same as starting auto tuning from front panel (At = 1).

At = 3. This configuration applies after auto tuning is done. Auto 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 control mode

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. However, 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. You can start the auto-tune any

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

the instrument executes the 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 the 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 need to 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 to enable the On/Off control mode.

When the temperature passes hysteresis band (Hy), the heater (or cooler) will

be turned off. When the temperature drops back to below the hysteresis band,

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.

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