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G
General notes
Design of temperature sensors in general:
Sensors are distinguished by shape type as follows: surface-contacting sensors, cable temperature sensors, and housing-type and built-in temperature sensors.
– On surface-contacting sensors, the temperature sensor has at least one contact area that must be brought in contact, e.g. with the surface of radiators or
pipes. If the contact area is not positioned correctly relative to the surface to be measured, significant temperature measurement errors may occur. Good
contact area and temperature conduction must be ensured, dirt and unevenness must be avoided, and heat-conductive paste is to be used where necessary.
– On cable temperature sensors, the temperature sensor is installed inside a sensor sleeve, from which a connecting cable is leading out. In addition to the
standard insulating materials PVC, silicone, and fibreglass with stainless steel texture, other versions are also available that may allow a wider range of
application.
– On housing-type sensors, the temperature sensor is embedded in a respective housing. Different designs of housing are available, e.g. with an external
sensor sleeve (see outside temperature sensor). Housing-type sensors are normally distinguished into in-wall and on-wall types and indoor and wet room
versions. Connection terminals are placed on a plate inside the connecting housing.
– Duct and built-in temperature sensors are distinguished into temperature sensors with interchangeable measuring insert and without interchangeable
measuring insert. Connection parts are placed inside a connecting head. Standard process connection for immersion sensors is a pipe thread (sizes in
inches) and a mounting flange for duct sensors. However, it may be designed differently. When a built-in sensor has a neck tube, the application range is
usually somewhat wider since ascending heat cannot flow directly and immediately into the connecting head. This is to be noted especially when trans mitters
are installed. The temperature sensor in built-in sensors is always placed inside the front part of the protective tube. On temperature sensors with short
reaction times, protective tubes are stepped.
NOTE !
Select immersion depth for built-in sensors so that the error caused by heat dissipation stays within the admissible error margins. A standard value is:
10 x diameter of protection tube + sensor length. In connection with housing-type sensors, particularly with outdoor sensors, please consider the
influence of thermal radiation. For that purpose, a sunshade and radiation protector can be attached. If the sensor is used in refrigeration circuits,
it must be insulated together with the housing to reduce the temperature potential between the device and the medium to a minimum and thus prevent
condensation damage.
Maximum thermal load on components:
On principle, all temperature sensors shall be protected
against unacceptable overheating!
Standard values for individual components and materials
selected are shown for operation under
neutral atmos phere and otherwise normal conditions
(see table to the right).
For combinations of different insulating materials,
the lowest temperature limit shall always apply.
G
Resistance characteristics of passive temperature sensors
In order to avoid damages ⁄ errors, preferably shielded cables are to be used.
Laying measuring cables parallel with current-carrying cables must in any case be avoided.
EMC directives shall be observed!
These instruments must be installed by authorised specialists only!
NOTE !
Testing current influences the thermometer's measuring
accuracy due to intrinsic heating and therefore,
should never be greater than as specified below:
Sensor current, maximum:
NI1000 (DIN EN 43760, class B) ......................... < 0.3 mA
Measuring accuracy at 0 °C:
NI1000 (DIN EN 43760, class B) ........................... ± 0.4 K
Component .............................................................. max. thermal load
Connecting cable
PVC, normal ................................................................................+70 °C
PVC, heat-stabilized ..................................................................+105 °C
Silicone ....................................................................................+180 °C
PTFE .......................................................................................+200 °C
Fibreglass insulation with stainless steel texture ........................+400 °C
Housing ⁄ Sensor
see table "Technical Data"
I
max
7
Ni 1000
° C
Ω
– 50
743
– 40
791
– 30
842
– 20
893
– 10
946
0
1000
+ 10
1056
+ 20
1112
+ 30
1171
+ 40
1230
+ 50
1291
+ 60
1353
+ 70
1417
+ 80
1483
+ 90
1549
+ 100
1618
+ 110
1688
+ 120
1760
+ 130
1833
+ 140
1909
+ 150
1987
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