Startup and operation
RES-409
Page 23
9.2.7
DIP switches for activating the
terminating resistance
The "Termination" DIP switch can be used to switch a
terminating resistance of 150ohms between the two
CAN lines (CAN-L and CAN-H). This switch must be set
to "ON" in order to activate the resistance.
9.3
Heatsealing band
9.3.1
General
The heatsealing band is a key component in the control
loop, since it is both a heating element and 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 applied for this system
necessitates a heatsealing band alloy with a suitable
temperature coefficient TCR, i.e. one whose resistance
increases as the temperature rises.
Too low a TCR leads to oscillation or uncontrolled
heating.
If a heatsealing band with a higher TCR is used, the
controller must be specially calibrated.
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 (
"Burning in the heatsealing band" on page 23).
One very important design feature is the copper or
silver-plating of the heatsealing band ends. Cold ends
allow the temperature to be controlled precisely and
increase the life of the teflon coating and the
heatsealing band.
An overheated or burned-out heatsealing
band must no longer be used because the
TCR has been altered irreversibly.
9.3.2
Burning in the heatsealing band
If a new heatsealing band has been used, the zero
point is first of all calibrated while the band is still cold
by activating the "AUTOCAL" function on the controller.
When the "AUTOCAL" function has finished, the
controller outputs the preselected calibration
temperature (default value: 20°C) as the ACTUAL
temperature at the analog actual value output as well
as in the controller status. Adjust the set point to
approximately 250°C and send a "START" command
with a heatup time of approximately 1 second
(
section 10.3.2 "START / STOP command "START"
signal" on page 31). After cooling down again, the
controller usually indicates a value less than 20°C.
Repeat the "AUTOCAL" function. The heatsealing
band has now been burned in and the change in the
alloying properties stabilized.
The burn-in effect described here does not occur if the
heatsealing band has already been thermally
pretreated by the manufacturer.
9.3.3
Replacing the heatsealing band
All power supply leads 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 manufacturer.
Each time the heatsealing band is replaced, the zero
point must be calibrated with the AUTOCAL function
while the band is still cold, in order to compensate
production-related resistance tolerances. The burn-in
procedure described above must be performed for all
new heatsealing bands.
9.4
Startup procedure
Please also refer to section 1 "Safety and warning
notes" on page 3 and section 2 "Application" on
page 4.
Installation and startup may only be
performed by technically trained, skilled
persons who are familiar with the associated risks
and warranty provisions.
9.4.1
Initial startup
Prerequisites: The controller must be correctly installed
and connected (
section 8 "Montage und Installation"
on page 11).
Proceed as follows to start up the controller for the first
time:
1. Switch off the line voltage and verify that all circuits
are deenergized.
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