BECKHOFF DK9222-0112-0059 - Manual (Page 7)

I/O
Measuring analog signals
Application Note DK9222-0112-0059
Correct multiple tapping of a current-based measured value
A =
KL3022
differential
input
KL3xxx
Single-
ended
4…20 mA
Fig. 5 Series connection of differential and single-ended inputs for the multiple tapping of a current-based measured value
Worth knowing
HART protocol
The HART communication (Highway Addressable Remote Transducer) also uses analog 4 – 20 mA technology in conjunction
with 2-wire sensors. HART describes remotely addressable transducers and is a function-oriented extension of the analog
current signal by the simultaneous superimposition of digital information. HART is typically used in the process industry where
it is frequently implemented in explosive zones, among other areas.
Systematic measuring error with user-specific scaling
4 mA are always needed for the sensor supply, as a result, the hub of 16 mA represents the process data information that must
be evaluated by the evaluation unit. Typical errors frequently result from an incorrectly adapted user scaling, which does not
map the zero point correctly.
High-energy overvoltage
For applications in which high-energy overvoltages are to be expected on the supply voltage, analog signals can be additionally
screened by the employment of a KL9540-0010 surge filter terminal from Beckhoff.
– Bus Terminals for analoge input signals www.beckhoff.com/KL3xxx
– Surge filter field supply for analog terminals www.beckhoff.com/KL9540-0010
– Potential distribution (0V | 24 V ) for eight 3-wire sensors www.beckhoff.com/KL9184
– Potential distribution (24 V ) for eight 2-wire sensors www.beckhoff.com/KL918
– Modular fieldbus system for automation www.beckhoff.com/Busterminal
New Automation Technology Beckhoff
For application notes see disclaimer on the last page