Kamstrup MAXICAL III, Руководство пользователя

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MAXICAL ® III
5511-229 GB/98.06/Rev. B1
8
The differential temperature is accurately calculated throughout
the whole measuring range - even with cooling down to 0.01°C.
Accuracy is, however, slightly affected below
D
t=3°C. If a
negative differential temperature is registered, this will be per-
ceived as 0.00°C. Energy registering will then stop.
MAXICAL
®
III measures temperature every 5 seconds, updating
the display and analogue outputs with the new reading. Prior to
each temperature measurement, the A/D converters zero point and
span is adjusted automatically, based on the internal precision
resistors. Flow and return temperatures are then measured twice,
the second measurement being taken a number of 10 msec. after
the first to ensure optimal damping of 50 Hz mains interference.
Depending on the type of meter selected, a set of either Pt100 or
Pt500 sensors must be connected (according to IEC 751). The
sensors must always be matched and 4-wire screened cable used to
connect the sensors to MAXICAL
® III, to ensure optimal preci-
sion. The cable screen must be connected at the MAXCIAL III
and not at the sensor housing.
In stand-by mode - i.e. when the supply is disconnected - tempera-
tures will be displayed without 4-wire compensation. Once the
supply has been connected, 4-wire compensation will eliminate
99% of the measuring error arising as a result of the length of the
cable.
When MAXICAL ® III is connected to a pipe with a large diam-
eter, average measuring must be established to reduce the influ-
ence of temperature fluctuation in the water. Average measuring
can be built up with 5 Pt100 sensors connected in series to a Pt500
input or with 4-sensors connected in parallel/series (Please refer to
chapter 4.3.1).
2.5. Permanent Memory
MAXICAL
®
III has an electronic, erasable programmable, read-
only memory (EEPROM) which stores data independent of the
power supply. All accummulated values are stored in the memory
at hourly intervals. At midnight each night, the following data will
be stored in a 31-day datalogger:
Date, Energy, Water, TA2, TA3, Alarm
Peak time and Peak power/flow.