Instructions for Use
– SCHMIDT
®
Flow Sensor SS 20.500
Page 25
Analog outputs
Switching characteristic Auto-U/I
Range of resistance value R
L
Signalling mode
Signalling range
≤ 500 (550)
Current (I)
4 ... 20 mA
> 500 (550)
Voltage (U)
0 ... 10 V
A hysteresis of approx. 50
ensures a stable transition behavior (see
Figure 5-2
Depending on the provided output signal accuracy of the mode switch-
ing point detection can be decreased. Therefore, it is recommended
to select the resistance in such a way that safe detection can be main-
tained (< 300
for current mode and > 1 k
for voltage mode).
To detect possible alternating load for an actual zero signal, the elec-
tronics generates test pulses that correspond to an effective value of
approx. 1 mV. However, latest measuring devices may trigger in re-
sponse to such a pulse in DC voltage measuring mode and display
short-term measuring values of up to 20 mV. In this case it is re-com-
mended to install an RC filter at the measuring input with a time con-
stant of 20 … 100 ms.
Error signaling
In current mode the interface outputs 2 mA
20
.
In voltage mode the output switches to 0 V.
Representation of measuring range
The measuring range of the corresponding measuring value is
mapped in a linear way to the signal range of its associated analog
output specific for this mode.
20
In accordance with NAMUR specification.
