Kamstrup MULTICAL 402, Техническое описание, Страница: 44 / 113

MULTICAL® 402
44
Kamstrup A/S · Technical Description · 5512-742_M1_GB_01.2016
7.6 Temperature measurement
Forward and return temperatures are measured by means of an accurately matched Pt500 or Pt100 sensor set.
During each temperature measurement MULTICAL

The display presents forward and return temperatures as well as the temperature difference in range 0.00
°
C to
165.00
°
C.
402 sends a 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 a possible low-frequency noise of 50 Hz (or 60 Hz), picked up via the sensor cables. Furthermore,
current measurements are made on internal reference resistors in order to secure optimum measuring stability.
Forward or return temperatures under 0
°
C are displayed as 0.00
°
C, and temperatures above 165
°
C are displayed
as 165.00
°
C. If one or both temperature sensors are outside measuring range, Info=008 (forward), Info=004
(return) or Info=012 (both sensors outside range) is set.
At negative temperature difference (forward
<
return) the temperature difference is displayed with a negative sign
and cooling energy is calculated (provided that the meter has been configured for cooling metering).
7.6.1 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
7.6.2 Average temperatures
MULTICAL

402 currently calculates the average temperatures of forward and return pipes (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
enumeration (e.g. with every 0.01 m
3
Type of registration
if the meter size is qp 1.5), whereas the display is updated every 24 hours.
The average temperatures are thereby volume weighted and can, thus, be used directly for checking purposes.
Average Yearly data Monthly data
Year-to-date average (since latest target date)
• •
Month-to-date average (since latest target date)
• •
Year-to-date average of T1
(Current date with a stipulated line under year or
month is shown immediately BEFORE this reading)