Autotune Mode - Burkert 8626 Instructions De Service

The control parameters are set such that changes in set value or disturbances are
compensated as rapidly as possible without causing appreciable overshoot.
After a jump in set value, the MFC Type 8626 reaches the ± 5% band about the new
set value within max. 500 ms and remains in this band thereafter.
The standard signal for the instantaneous value output is filtered in order to reduce
the strong fluid noise occurring especially with large flow rates. For this reason, the
analogue output signal (process value) does not fully reflect the high control
dynamics of the MFC Type 8626.
NOTE

3.4.2 Autotune mode

è The autotune function (valve adjustment) is triggered by connecting pins 7
and 8 of the SUB-D connector together for at least one second, e.g. with a
switch.
è Make sure that the pressure conditions typical of the application are present.
As long as the autotune function is being processed, the red autotune lamp in the
LED display area flashes.
ATTENTION!
During the autotune routine, the MFC Type 8626 is not in control, but the internally
defined set value is transmitted to the valve as the correcting variable. The pulse-
duty factor of the PWM signal is run through in small steps from 0 to 100%. The
values at which the valve just begins to open or reaches the maximum flow rate are
determined and written in the EEPROM.
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To assess the actual dynamic characteristics of the MFC Type
8626, such as the 3dB frequency or the response to a set point
change, theactual flow value should be recorded on an
oscilloscope with an external, undamped flow sensor.
The autotune function runs automatically and cannot be
influenced in any way.
è In no case should the power supply to the MFC Type 8626
be switched off (if there is a power failure during the end
phase, undefined values may be assigned to
the variables in the EEPROM).
è Keep the pressure constant.
Type 8626