KROHNE H54 M4 EN - Manual (Page 13)

13 H54 Installation and operating instructions
9 Electrical signal output ESK II
9.1 Electrical
connection
The connecting terminals of the M9 display have a pluggable design and can be removed in order to
connect the lines.
9.2 HART
TM communication with the ESK II
HART TM communication is not compellingly required in order to operate the ESK II.
When HART TM communication is carried out with the ESK II, this does not by any means impair analog
measured value transfer (4...20mA).
Exception at Multidrop operation. In Multidrop operation a maximum of 15 instruments with HART TM
function can be operated in parallel, whereby their current outputs are switched inactive (approx. 4 mA).
If a HART TM communicator (type Fisher Rosemount, Model 275) or a PC with HART TM modem is
used, the resistor which is connected in series (R
ext.
) has to exceed 250 Ohms.
In this type of operation the auxiliary power must amount to at least 18 V. The communicator or the PC
is connected as shown in the drawing above.
It can be operated optionally via the connecting terminals of the ESK II (2) or via an external resistance
(1) connected in series. The counter cannot be read out or operated by means of HART TM
communication!
9.3
Technical data of ESK II
Auxiliary power 12 (18 * ) to 30 V DC
Measurement signal 4.00 to 20.00 mA for 0 to 100 % flow value
> 20.8 mA for alarm status
Auxiliary power influence < 0.1%
Dependency on external resistance < 0.1%
Temperature influence < 5 µA / K
Max. external resistance / load 0 (250 * ) to 800 Ohms
* These values are to be observed as minimum values during HART TM communication.