WIKA Operating Instructions Level Transmitter
– BLM-SF-FM
29
5. Analog output
The transmitter incorporates an analogue 4-20 mA output. The primary
value (PV, see chap. 4.2.2.11) is transformed to the 4-20 mA range. The
offset is at 4 mA, the span at 20 mA.
The transmitter over steers the current limits according to NAMUR NE 43,
i.e. the minimum current is 3.8 mA and the maximum current is 20.5 mA.
In the case of error (e.g. defective electronics), the current will be set to
>21 mA or <3.6 mA (se
lectable). If “hold last value” has been set in the
4-20 mA-menu, the last good current is kept.
Attention:
In multidrop-
mode (available in the “HART”-menu), the
transmitter output will be fixed at 4 mA. Transmission of
the measured values is available over the HART®-protocol
only.
The setting of the analogue output is possible, as described in chap. 4.2.2.
Furthermore, a transfer function (see 4.2.4.3) can be used to select a non-
linear response of the analogue output. This can be used e.g. to drive a
valve directly with the analogue output.
