Endress+Hauser Waterpilot FMX21, Руководство по эксплуатации

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Electrical connection Waterpilot FMX21
32 Hauser
6.6.4 Connecting for air pressure compensation with external
measured value
FXN520
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2
3
4
A0018757
1 Fieldgate FXA520
2 Multidrop Connector FXN520
3 Cerabar
4 Waterpilot FMX21
For applications in which condensation may occur, the use of an absolute pressure probe is
recommended. For level measurement using an absolute pressure probe, the measured
value is affected by fluctuations in the ambient air pressure. To correct the resulting
measured error, you can connect an external absolute pressure sensor (e.g. Cerabar) to the
HART signal line, switch the Waterpilot to burst mode and operate the Cerabar in the
"Electr. Delta P" mode.
When you switch on the "Electr. Delta P" application, the external absolute pressure sensor
calculates the difference between the two pressure signals and can thus determine the
level precisely. Only one level measured value can be corrected in this way.
For additional information, see →  56.
If using intrinsically safe devices, the regulations which apply to interconnecting
intrinsically safe circuits as outlined in IEC 60079-14 (proof of intrinsic safety) must
be observed.
6.6.5 Connecting an external temperature sensor/temperature head
transmitter for density compensation
The device can correct measured errors that result from fluctuations in the density of the
water caused by temperature. Users can choose from the following options:
Use the internally measured sensor temperature of the device
The internally measured sensor temperature is calculated in the device for density
compensation. The level signal is thus corrected according to the density characteristic line
of water.
Use the optional internal Pt100 temperature sensor for density compensation in a
suitable HART master (e.g. PLC)
The Waterpilot FMX21 is available with an optional Pt100 temperature sensor. To convert
the Pt100 signal to a 4 to 20 mA HART signal, Hauser also offers the TMT72
temperature head transmitter. The temperature and pressure signal is queried by a HART
master (e.g. PLC), where a corrected level value can be generated using a stored
linearization table or density function (of a chosen medium).