Startup and operation
Page 18
RES-5012
Version 2
7.2.4
Configuration of the alarm relay
If the switch is set to "Alarm relay de-energized at alarm / PC CONFIGURATION", you can select more alarm
output configurations in the ROPEX visualization software (
section 8.12 "USB interface for visualization soft-
7.3
Replacing and burning in the heatsealing band
7.3.1
Burning in the heatsealing band
The heatsealing band is a key component in the control loop because it is not only a heating element but also a
sensor. The geometry of the heatsealing band is too complex to be discussed at length here. We shall therefore
only refer to a few of the most important physical and electrical properties.
The measuring principle used for this system requires a heatsealing band alloy with a suitable temperature coef-
ficient TCR. Too low a TCR leads to oscillation or uncontrolled heating.
If a heatsealing band with a higher TCR is used, the controller must be calibrated for it.
The first time the heatsealing band is heated to approximately 200…250 °C, the standard alloy undergoes a once-
only resistance change (burn-in effect). The cold resistance of the heatsealing band is reduced by approximately
2…3%. However, this at first glance slight resistance change results in a zero point error of 20…30 °C. The zero
point must therefore be corrected after a few heating cycles, i.e. the AUTOCAL function must be run again.
To do this, the system must be cooled off completely.
After the first heating and zeroing, the heating element is burned in and the change of resistance stabilised. The
heating element can now be used.
The burn-in effect described here does not occur if the heatsealing band has already been thermally pretreated
by the manufacturer.
An overheated or burned-out heatsealing band must no longer be used because the temperature
coefficient has been irreversibly altered.
A very important design measure is copper-coating or silver-coating of the heating element ends. The thermal
characteristics change in this range through coating of the heating element ends. As a result, the ends remain
cold, which permits exact temperature control and increases the useful life of the heating element.
7.3.2
Replacing the heatsealing band
The supply voltage (all poles) must be disconnected from the RESISTRON
®
temperature controller in order to
replace the heatsealing band.
The heatsealing band must be replaced in accordance with the instructions provided by the manu-
facturer.
0
5
1
2
3
4
6
7
8
9
AU
X
CONF
IG
URATI
ON
ALARM
O
UTP
UT
ENER
GIZ
ED
(A
T AL
ARM)
DE-E
NERG
IZ
ED
Alarm relay contact
opened by alarm/
PC-CONFIGURATION
Alarm relay contact
closed by alarm.
(factory setting)
!
!