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MULTICAL® 803
114
Kamstrup A/S · Technical description · 5512-2360_A1_
GB
_02.2019
7.6
Temperature measurement
Inlet and outlet temperatures are measured by means of an accurately matched Pt500 or Pt100 sensor pair. During
each temperature measurement, MULTICAL® 803 sends measuring current through each sensor. The current is
approx. 0.5 mA for Pt500 and approx. 2.5 mA for Pt100. 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 the range 0.00
°
C to 185.00
°
C.
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 the measuring range,
the info code is set as shown in paragraph 7.8.
At a 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 the temperature difference appears
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.
Pt100
Pt500
Measuring
current
<
2.5 mA
<
0.5 mA
Peak power
<
1.0 mW
<
0.2 mW
RMS influence
(fast mode)
<
10
µ
W
<
2
µ
W
RMS influence
(normal mode)
<
2
µ
W
<
0.4
µ
W
Volume-based average temperatures
MULTICAL® 803 calculates the current average temperature of inlet and outlet (t1, t2 and t3) in full
°
C and the
background calculations E8, E9, E10 and E11 are made for each integration determined by the calculator’s
integration time (L code). The average calculations are thus volume-weighted and can be used directly for checking
purposes.
Preprogrammed temperatures
The temperatures t2, t3 and t4 can either be measured or programmed in the calculator's memory while
temperature t5 can only be programmed. The temperature input t2 is a legal input, which means that this cannot be
programmed on an approved heat meter, cooling meter or bifunctional heat/cooling meter.
See paragraph 7.1 for examples of the use of these extra temperatures.