MULTICAL® 403
Kamstrup A/S · Technical description · FILE100000166_B_EN-55121689_M1_07.2023
7.6 Temperature measurement
Inlet and outlet temperatures are measured by means of an accurately matched Pt500. During each temperature
measurement MULTICAL
403 sends measuring current through each sensor. The current is approx. 0,5 mA for
Pt500. Two measurements are carried out in order to suppress possible 50 Hz (or 60 Hz) low-frequency noise picked
up via the sensor cables. Furthermore, current measurements are made by internal reference resistors in order to
secure optimum measuring stability.
The display presents inlet and outlet temperatures as well as temperature difference in range 0,00 °C to 185,00 °C.
The temperature difference is presented in the range 0,01 K to 185,00 K.
By default, the meter has no cut-off for low temperature and thus measures down to 0,01 °C and 0,01 K. If required,
it is possible to program a cut-off for the temperature difference (ΔΘ) in the range 0,01…2,50 K. It is not possible to
program this with METERTOOL. If the meter is programmed with a cut-off of 2,50 K, it will not calculate energy and
volume at a temperature difference below 2,50 K.
Note Cut-off for the temperature difference should be distinguished from θ
hc
, which functions as a limit value of the
heat/cooling energy measurement. See paragraph 7.3.
Inlet or outlet temperatures below 0 °C and above 185 °C are indicated as lines in the display, but serial reading
includes 0,00 °C and 185,00 °C respectively. If one or both temperature sensors are outside measuring range, the
info code is set as shown in the next paragraph.
At negative temperature difference (inlet < outlet) the temperature difference is displayed with a negative sign and
cooling energy is calculated. It depends on the selected DDD-code whether this appears from the reading in the
display.
Measuring current and power
Measuring current is only sent through the temperature sensors during the short duration of the temperature
measurement. The effective power that is deposited in the sensor elements is thus very small, and its influence on
self-heating of the temperature sensors is typically less than 1/1000 K.
< 0,5 mA
< 0,2 mW
(fast mode)
< 2 µW
(normal mode)
< 0,4 µW
Average temperatures
MULTICAL
403 continuously calculates the average temperatures of inlet and outlet (t1 and t2) in °C without
decimals, and background calculations E8 and E9 (m
3
x t1 and m
3
x t2) are carried out with every volume calculation
(e.g. with every 0,01 m
3
if the meter size is qp 1,5), whereas the display is updated with every integration (depending
on L-code). The average calculations are thus volume weighted and can be used directly for checking purposes.
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