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The next three parameters - Proportional (PB) Integral (+i) and Derivative (+d) - are the three control
parameters of a P.l.D. control system. These parameters will be set when you tune your furnace. (See
Self-Adaptive Tuning.)
Pb - Proportional.
(+i) - Integral.
(+d) - Derivative.
The next two parameters - cutback low (cbl) and cutback high (cbh) - are to aid the control in preventing
temperature overshoots and undershoots. The point from setpoint where the power starts "cutting back"
is defined as the cutback value. These values are also automatically adjusted by the Self Tuning and
Adaptive Tuning features. These values cannot be changed by the user; the controller automatically
installs optimum cutback values when in Self Tuning and Adaptive Tuning.
HL - Output Power limits the average maximum power that is applied to the heating elements. Normal
setting is 100%. If you plan to use the furnace below 260°C (500°F) the output power may be reduced.
This will significantly shorten the time it takes for stabilization. It will also reduce drastic temperature
overshoots. Contact Barnstead/Thermolyne Customer Service for advice on the proper value to use.
Remember that this parameter does not reduce the voltage to the elements. It reduces the average
power to the elements by cycling power on and off.
HC - Cycle Time is the rate at which power is supplied to power control switch. Push up or down button
to set.
Sbr - the percent of power that is supplied to the control output terminals if an open thermocouple
condition exists. Push up or down button to check. 0.0 will be displayed. This parameter cannot be
changed; if 0.0 is not displayed, contact Barnstead/Thermolyne. The upper display will flash "OR" if an
open thermocouple condition exists.
Tuning Your Controller
The programmable control has automatic tuning features which install optimum tuning parameters to give
the best temperature accuracy. No manual loading of tuning parameters is needed. We highly
recommend using these features to provide the best temperature accuracy the controller can attain.
Perform the following procedures when you first set up your furnace and each time you change your load
type, operating temperature, or program.
The following procedure is instruction on how to initiate the SAT Self and Adaptive Tuning feature. This
feature starts the controller in the Self Tune mode then automatically switches over to the Adaptive
Tuning Feature. Self Tuning is a one-time function which permits the user to retune the instrument control
parameters to suit new process conditions. Adaptive tuning takes over when the self tune is completed
and continuously reevaluates the tuned parameters. Adaptive tuning will then automatically install new
values if a better response could have been attained.
To initiate the tuning feature:
Load your furnace with a load characteristic of those you intend to heat in it.
Depress scroll button until SAT is displayed. Depress the up and down buttons simultaneously to start
self tuning. The A-T indicator is then illuminated (upper right hand comer) and the lower display indicates
the setpoint at which the self-tune sequence will occur. The "SP" indicator will flash for 1 minute, during
which time the setpoint may be changed, if it is required to retune at a new setpoint either above or below
the process value indicated on the upper display. (If you will be using the controller as a single Setpoint
Controller, set the furnace's setpoint to the temperature you intend to use for your application. If you will
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