Datasheet

13
Application Examples for Avoiding Corruption of Analog Signals
Input Output
857-400
PLC
(WAGO-I/O-SYSTEM 750)
0,00
PLC
(WAGO-I/O-SYSTEM 750)
6,54
Ground1 Ground2
Ground1 Ground2
Ground current loop
No ground current loop
I
Loop
I
Loop= 0
I
ges
I
Δ
Potential Difference
Signal Filtering
Linked Measurement Circuits
A frequent cause of potential differences is linked
measurement circuits for which the reference vol-
tage is raised by combining several signal circuits.
Thanks to the use of isolation amplifiers, this problem
is eliminated since galvanic isolation of the isolation
amplifier eliminates the influence of various reference
voltages.
If the signal to be processed is burdened with distur-
bances, it is freed of the disturbances by the signal
filtering with an internal filter in the input of the iso-
lation amplifier. The signal is then transmitted to the
superior controller. This way, the devices can be ad-
apted flexibly to the frequency range in which the
disturbance lies using DIP switches. The disturbances
are thus filtered out safely.
In this instance, an isolation amplifier helps sin-
ce it prevents the arising of a ground current loop.
Galvanic isolation of the input circuit from the output
circuit breaks up this ground loop and enables per-
fect signal transmission. Smaller overvoltages with a
lower energy level that can arise due to switching
operations are dissipated safely. In addition, the out-
put side downstream controller is protected by the
galvanic isolation.
The main cause of analog signal corruptions are po-
tential differences that arise. With increasing trans-
mission lengths, the ground resistance increases.
Thus, differences of up to 200V can arise. With si-
gnals having ground reference, these ground loops
can cause corruptions since particular parts of the
signal are not transmitted via analog line, but via
ground. Thus, there is a faulty signal assessment.
In industrial applications, there are several requirements for safe and economical signal matching that demand appropriate so-
lutions. This is precisely where the strengths of analog technology lie. For years it has been used successfully in all branches of
industry, including factory automation and process technology.
The 857 Series JUMPFLEX
®
Transducers make a solid contribution to system safety for many problems that occur by
providing a continuous galvanic 3-way isolation with test voltages of 2.5kV between all channels (input/output/supply).
0 V … 10 V 0 V … 10 V
Input Output
857-400
24VDC
230VAC
PLC
(WAGO-I/O-SYSTEM 750)
RL 4 RL 3 RL 2 RL 1
ΔUR 4 ΔUR 3 ΔUR 2 ΔUR 1
857-400 857-400 857-400