Parameters For The Management Of The Temperature Sensors - Carel IR32M Manual

/ = Parameters for the management of the temperature sensors

SENSOR PARAMETERS
/0 Type of sensor (0=NTC, 1=PTC)
/C Calibration
/2 Stability measurement
/3 Sensor reading speed
/4 Virtual sensor
°C / °F (0=°C,1=°F)
/5
/6 Decimal point (0=yes, 1=no)
Note: for the set times to become operative, the instrument must be switched off and on again.
Short descriptive note about sensors with thermistors types NTC and PTC:
Equipment of the IR32 series is designed to work with NTC Carel temperature sensors, or sensors using
thermistors with a negative characteristic (NTC stands for Negative Temperature Coefficient). This type of
thermistor modifies an electrical parameter (its own resistance) in inverse proportion to any change in
temperature; that is, the resistance falls as the temperature rises, and vice versa. Other types of thermistor
are on the market. Widely available are PTC thermistors with a resistance of 985 Ohms at 25°C. PTC stands
for Positive Temperature Coefficient; by contrast with the NTC, these increase their resistance directly
according to the temperature increasing. As you can see in the diagram below, (the horizontal axis
represents the operating range, the vertical axis the error), the NTC type of sensor shows greater accuracy
than the PTC version. This is why the NTC sensors have been adopted as standard.
-30
Variation of PTC 985 Ohm probe at 25°C
It is nevertheless possible to use Infrared equipment with PTC sensors of the 985 Ohm, 25°C type by
specifying the model required.
/0: Type of sensor
This parameter is displayed only during the reset procedure (see relative chapter). On equipment with a
serial number less than 5000 the parameter /0 is displayed whenever access is gained to type C parameters.
On this point please refer to the specific note at the end of the manual. The parameter /0 allows users to
specify the type of sensor being used, i.e. whether NTC (/0=0) or PTC (/0=1). As indicated previously, it is
emphasised that IR32 equipment is normally designed to work with NTC sensors. To be able to work with
PTC sensors rather than NTC, a modification is required which can only be carried out in the factory, and it
is not enough to shift the parameter /0 to =1. If PTC sensors are to be used, therefore, it is essential to
specify the requested code at the time of ordering (see chapter 'Ordering codes 'I).
Parameter /0 is useful in only one situation: that is where the equipment has been acquired to work with a
PTC sensor and, in addition, due to serious malfunction, it has been reset (see "Reset procedure"). After the
reset, the microprocessor installs the parameter /0=0, which is the value intended for the NTC sensor and
therefore incompatible with hardware designed for a PTC sensor. In such an event it is necessary to operate
manually to set the parameter /0 to the correct value, i.e. /0=1 (operation with PTC sensor). Any other use
can cause malfunctioning.
Default for standard models /0=0
Default for PTC models /0=1. Available on all panel mounting models
Maximun variation shown by types NTC and PTC temperature probes in
relation to intended theoretical values .
-25 -20 -15 -10
Type
C
F
C
C
C
C
C
-5 0 5 10
3
Variation of Carel NTC probe
2
1
0
-1
-2
-3
-4
16
Min. Max. Unit
0 1 -
-20 +20 +C/+F
1 15 -
1 15 -
0 100
0 1 flag
0 1 flag
15 20 25 30
Cod. +030220151 - Rel. 2.1 - 04/09/98
Def
0
0.0
4
8
0
0
0