TECHNICAL DESCRIPTION MULTICAL
®
401
5512-091 GB/02.2008/Rev. J1
35
7.7 Temperature measurement
The temperatures in flow and return are measured by an accurately matched Pt500 and Pt100 sensors. During
each temperature measurement MULTICALÒ 401 sends a measuring current through each sensor, approx. 0.5 mA
for Pt500 and 3.0 mA for Pt100. 2 measurements are made to suppress any 50 Hz ripple collected via the sensor
cables.
In addition, measurements are constantly made on internal reference resistances to ensure optimal measuring
stability.
When the measurement current runs through the sensors, a peak power of
0.2 mW is left in each sensor, which
corresponds to an average power of
1 W in ”normal mode” or 5 W in ”fast mode”.
Flow and return temperatures and the temperature difference from 0.00
C to 165.00C are displayed.
Flow or return temperatures under 0
C are displayed as 0.00C, and temperatures over 165C are shown as
165.00
C. When one or both temperature sensors are outside the measuring range, Info=008 (flow), Info=004
(return) or Info=012 is set when both sensors are outside the measuring range.
In connection with negative temperature difference (flow
return) the temperature difference is shown as 0.00C,
energy is not calculated.
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