Instructions for Use
– SCHMIDT
®
Flow Sensor SS 20.600
Page 21
Operating voltage
The flow sensor
SS 20.600
is protected against reverse polarity of the
operating voltage. For its intended operation, it requires a DC voltage of
24 V
DC
with a tolerance of ±20 %.
Deviating values can lead to measurement errors or even defects and,
therefore, should be avoided.
Operate the sensor only within the defined voltage range
(24 V
DC
± 20 %).
Undervoltage may result in malfunction; overvoltage may lead to
irreversible damage.
The specifications for the operating voltage apply to the connection of the
sensor. Voltage drops generated due to line resistances must be taken
into account by the customer.
The typical operating current of the sensor (at nominal operating voltage,
analog signal currents included, but without any of the impulse outputs) is
approx. 80 mA, at maximum
15
it requires 200 mA.
Wiring of analog outputs
Both analog outputs for flow and temperature are designed as high-side
driver with “Auto-U/I” feature and are short-circuit protected against both
rails of the operating voltage.
Use of only one analog output
It is recommended to connect the same resistance value to both analog
outputs, even if only one of them
is used. For example, if only the “flow”
output is operated in current mode with a resistance value of a few
ohms, it is recommended to connect the other analog output (“medium
t
emperature”) with the same resistance value or directly to AGND.
Nominal operation
The load resistance R
L
must be connected between the corresponding
signal output and the electronic reference potential of the sensor (see
Figure 4-2). Normally, AGND must be selected as measuring reference
potential for the signal output. The supply line GND can also be used
as reference potential, however, the ground offset can cause significant
measurement errors in “Voltage” operating mode.
Typically, AGND has to be selected as measuring reference
potential for the signal output.
15
Supply voltage minimal, both signal outputs with 22 mA, maximum signal current of im-
pulse output, without signal current of
otuput “Pulse “ (relay).
