MULTICAL® 803
134
Kamstrup A/S · Technical description · 5512-2360_A1_
GB
_02.2019
9
Temperature sensors
A platinum resistance thermometer utilizes that the precious metal platinum has a very well-defined coherence
between its resistance and temperature. The coherence between the resistance and the temperature is defined in
the standard EN 60751 (DIN/IEC 751), and tables with examples of the coherence are available in paragraph 9.7. On
MULTICAL® 803, Pt100 and Pt500 temperature sensors can be used where the nominal resistance at 0 °C is 100 Ω
and 500 Ω, respectively.
The coherence between the resistance
R
t
and the temperature
t
is defined by:
𝑅𝑅
𝑡𝑡
=
𝑅𝑅
0
(1 +
𝐴𝐴𝐸𝐸
+
𝐵𝐵𝐸𝐸
2
)
where
R
0
indicates the resistance at 0.00 °C, while
A
and
B
are constants. The values
R
0
,
A
and
B
are determined by
the verification of the temperature sensor, which is carried out, cf. EN 1434-5.
On a heat or cooling meter, a temperature sensor pair is used for measuring the temperature difference between
inlet and outlet. As each of the two temperature sensors have their own values for
R
0
,
A
and
B
, the requirement for
an approved temperature sensor pair according to EN 1434-1 is that the maximum difference in percentage
between the two temperature sensors,
e
t
, in the entire approval area must not exceed:
𝐸𝐸
𝑡𝑡
= ±
�
0.5 + 3
∆𝜃𝜃
𝑚𝑚𝑚𝑚𝑚𝑚
∆𝜃𝜃 �
where Δθ is the specific temperature difference and Δθ
min
is the smallest approved temperature difference, typically
3 K. The values
R
0
,
A
and
B
of the individual temperature sensors and
E
t
appear from the certificate of the
temperature sensor pair.
9.1
Cable influence and connection of cables
For small and medium-size heat meters, mostly only relatively short temperature sensor cable lengths are needed,
which means that 2-wire sensor pairs can be used with advantage. By default, MULTICAL® 803 is prepared for 4-wire
connection. The use of 2-wire sensor pairs requires the installation of the short-circuit jumper as shown in the figure
below.
The cable
lengths and
cross sections
of the two sensors, which are used as 2-wire temperature sensor pair for a heat meter, must always be identical, and
cable sensors must neither be shortened nor extended.
2-W Jumper