Commissioning and operation
Version 1
RES-5006
Page 17
7.2.4
Configuration of the alarm relay
When the “Alarm relay contact opens with Alarm/PC CONFIGURATION” is selected, additional configurations for
the behaviour of the alarm output can be set through the ROPEX visualisation software (
interface for visualisation software ROPEXvisual
7.3
Replace and burn in heating element
7.3.1
Burning in the heating element
The heating element is an important component in the control circuit, as it is both a heating element and sensor.
The geometry of the heating element cannot be discussed here due to its diversity. Accordingly, only some impor-
tant physical and electrical characteristics are pointed out here:
The measurement principle used here requires from the heating element alloy a suitable temperature coefficient
TCR. A TCR that is too small results in vibrating of the controller or overheating of the heating element.
If the TCR is large, the controller must be calibrated for it. The RESISTRON
®
temperature controller is suitable for
temperature coefficients in the range 400…4000 ppm/K.
The first time it is heated to approx. 200…250 °C, the usual alloy undergoes a one-time change in resistance
(burn-in effect). The cold resistance of the heating element is reduced by about 2…3%. But this small change in
resistance generates a zero point error of 20…30°C. The zero point must therefore be corrected after a few
heating cycles, that is, the AUTOCAL function must be carried out 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 need to be considered if the manufacturer pretreated the heating ele-
ment for this purpose.
A damaged or worn-out heating element may no longer be used due to an irreversible TCR change.
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.
Alarm relay contact
opened by alarm/
PC-CONFIGURATION.
Alarm relay contact
closed by alarm.
(factory setting)
0
5
1 2
3
4
6
7
8
9
AUX
CONF
IG
URA
TIO
N
ALARM
O
UT
PU
T
ENER
GIZ
ED
(A T
AL
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M )
DE-E
NER
GIZ
ED
!