Instructions for Use
– SCHMIDT
®
Flow sensor SS 20.260
Page 11
4 Electrical connection
The sensor is equipped with a 4-pin cable firmly fixed to the sensor enclo-
sure (pin assignment refers to Table 4).
Wire color
Designation
Function
Brown
(BR)
Power
Operating voltage: +U
B
White
(WH)
GND
Operating voltage: Ground
Yellow
(YE)
Analog w
N
Output signal: Flow velocity
Green
(GN)
Analog T
M
or
AGND
Output signal: Temperature of medium
or
Ground connection of analog output
Table 4
During electrical installation ensure that no voltage is applied and
inadvertent activation is not possible.
The cable has a standard length of 2 m, but lengths of 3 up to 100 m can
be ordered optionally.
Operating voltage
For proper operation the sensor requires DC voltage with a nominal value
of 24 V with permitted tolerance of ±10 %. It is protected against a polarity
reversal; typical operating current is 40 mA, at maximum 60 mA
7
.
Only operate sensor within the defined range of operating volt-
age (24 V DC ± 10 %).
Undervoltage may result in malfunction; overvoltage may lead to
irreversible damage to the sensor.
The specifications for the operating voltage are valid for the internal con-
nection of the sensor. Voltage drops generated due to cable resistances
must be considered by the customer.
Analog outputs
The basic sensor variant
(“-1”), which measures only flow velocity, can be
ordered with voltage
8
(0 … 10 V) or current interface (4 … 20 mA). The
enhanced version (“-2”) with an additional analog output for signalizing
medium temperature comes with 2 current interfaces. Either type of ana-
log output is short-circuit protected against both rails of the operating volt-
age U
B
.
7
Both signal outputs 22 mA (maximum measuring values), minimum operating voltage.
8
It is recommended, to use AGND as measuring reference potential for voltage output.
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