Schmidt SS 20.600, Инструкция по эксплуатации

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Instructions for Use
– SCHMIDT
®
Flow Sensor SS 20.600 Page 22
Figure 4-2
Depending on the value of load resistance R
L
, the electronics switches
between operation as voltage interface (mode:
“U”) and current inter-
face (mode:
“I”) automatically, hence the designation “Auto-U/I”. The
switching threshold is in range between 500
… 550 Ω (for details refer
to chapter 5 Signaling ).
However, in voltage mode a low resistance value may cause significant
voltage losses via the wire resistances R
W
of the connection cable
which can lead to measuring errors
(“mass offset”).
For voltage mode, a measuring resistance of at least 10 k
Ω is
recommended.
The maximum load capacitance C
L
is 10 nF.

Short circuit mode
In case of a short circuit against the positive rail of the supply voltage
(+U
B
), the signal output is switched off.
In case of a short circuit against the negative rail (GND) of the operating
voltage, the output switches to current mode (R
L
is calculated to 0

)
and provides the required signal current.
If the signal output is connected to +U
B
via a resistance, the value R
L
is
calculated incorrectly and false signal values are caused.