BECKHOFF DK9222-0112-0059 - Manual

I/O
Measuring analog signals
Application Note DK9222-0112-0059
Keywords
Loop-powered
2-wire transmitter
True Zero
4-20 mA
KL3458
Analog
Single-ended
Current loop
Loop power
Live Zero
KL3454
KL3054
Difference
Input
Analog signal transmission: Current interface 4…20 mA
(Live Zero principle)
This application example describes the facets of analog signal recording and their forms of transmission in
general. In particular, this document covers the recording of measured values using the KL3054, KL3454 and
KL3458 analog input Bus Terminals from Beckhoff. When used in conjunction with 2 or 3-wire sensors, these
terminals enable the detection of cable breakage and sensor failures internally in the circuit according to
the Live Zero principle.
Analog signal recording
Analog measured variables such as pressure, temperature, flow, speed, etc. are converted by sensors into analog values and,
depending on the sensor, are also linearized inside the sensor. Sensors for analog measured variables usually consist of two
functional elements – the measuring sensor and the transducer – and determine the change in the measured variable by
means of a physical principle. The digitized analog signal transmitted to the controller normally corresponds to a standardized
level and is always composed of the type (voltage, current, resistance, etc.) and the value (0 – 10 V, ± 1 V, 0 – 20 mA, 500 mΩ,
etc.)
New Automation Technology Beckhoff 1
For application notes see disclaimer on the last page