7
3.2.4. Determining the reference resistance: (5.7.2.) The reference resistance of the heating conductor
(Rref) is determined in this step. A reference temperature of 0...50 °C must be set in the controller for
calibration. During calibration, the heating conductor must be at the reference temperature to ensure that
regulation is exact. By standardizing the voltage signal (Vr) and the current signal (Ir), the reference resistance
for the different temperature coefficients is always within the same resistance range. If 20 °C has been selected
as the reference temperature, then heating conductor's R20 is directly determined as the reference resistance.
If a heating conductor temperature other than 20 °C has been selected for calibration, then the determined
reference resistance corresponds to the temperature coefficient above or below the value for the R20. The
reference resistance is displayed for one second at calibration step 4 as the actual value and at the actual
value output. With a reference temperature of 20 °C an actual value of
70…80 % of the set temperature range of the controller is displayed or the voltage at the actual value output
is 7 –8 V. The actual value display is between 60 to 100% for the whole reference temperature range of 0 to
50 °C and the voltage at the actual value output is between 6 and 10 V.
3.2.5. Temperature reference time: ( 5.7.3.) The aim of the temperature reference time is to ensure that the
reference resistance can only be determined when the heating conductor has completely cooled down. The
actual value display is counted down during the reference time from 100 % to 0 % of the set temperature range
of the controller. During this reference time, the signal at the actual value output declines from 10 V to 0 V.
Times of 15 or 30 s can be chosen for the temperature reference time.
3.2.6. Checking the reference resistance: The reference resistance is checked after the temperature
reference time is finished. If calibration takes place on a heating conductor that has cooled down still further
during the temperature reference time, the entire calibration will be discarded and the procedure automatically
restarted. Once the reference resistance has been successfully checked, the PIREG-D2calculates the R20
(resistance at 20°C) of the heating conductor from the reference temperature set, the temperature coefficients
selected and the reference resistance (Rbez.) determined.
The reference resistance measured is displayed for one second as the actual value and at the actual value
output. The same value must be shown on the display or the same value must be set at the actual value output
as when the reference resistance was determined ( 3.2.4).
3.2.7. Determining the P-factor: The P-factor of the sealing transformer/heating conductor combination is
determined by heating with a constant correction variable. The heating conductor is either warmed by a
maximum of approx. 60 K or charged for a maximum of 120 network periods with a defined control value.
The total amplification of the control system is calculated from the measurement of the power fed into the
heating conductor and the measurement of the temperature increase of the heating conductor. The P-factor
for the PIREG-D2is calculated from this.
In the case of adverse conditions of the sealing transformer and heating conductor combinations or the public
supply the P-factor of the PIREG-D2can be corrected manually within a range of 30…110 % ( 5.2.5. and
4.9.).
3.2.8. Setting an initializing remanence: Soft switch-on procedure is carried out by setting an initializing
remanence to switch on the sealing transformer without current surge following a calibration. Setting an
initializing remanence takes 80 ms for the El- and 300 ms for toroidal core transformers (with 50 Hz mains
frequency).
3.2.9. Temperature coefficient correction: Differences of temperature coefficients can be corrected using
this function. These result from the dispersion of the metallurgical composition of the heating conductors.
In calibration stage 9, the PIREG-D2gradually heats up the heating conductor in eight temperature increments
or stages. The PIREG-D2compares its actual value temperature with the actual temperature of the heating
conductor, which it receives as a target value or directly as a measured temperature value from the TM6
thermometer.
The size of each increment is a result of the selected temperature range. The first temperature increment is
always 50 °C. The temperature of the eighth temperature increment falls 20% below the final value of the
selected temperature range. The six other temperature increments are equidistant between these points. For
the 300 °C temperature range, this gives the temperatures 50, 77, 104, 131, 159, 186, 213 and 240 °C. For
the 500 °C temperature range, this gives the temperatures 50, 100, 150, 200, 250, 300, 350 and 400 °C.
The actual temperature of the heating conductor must be set as target value in the display unit or reported
back directly to the PIREG-D2as a measured value of the TM6 thermometer via the RS232 interface.
Deviations of up to ±20 % between the calculated actual value temperature and the actual temperature of the
heating conductor can be corrected ( 5.7.4. und 4.9.). The correction process is controlled with the
“Start”/”Heat” option from the Working menu, the Start signal or via the “SSTST” command. The correction
process can also run automatically when the TC correction heating time was correspondingly set.
After a corresponding setting the TC temperature coefficient correction can be saved so that it doesn’t need
to be repeated after a new calibration but only when the heating conductor is replaced ( 5.2.5.).
Performing the temperature coefficient correction:
