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3.2
Selecting the supply voltage
The CT 24 operates as a so-called 2 wire current
transmitter. This means that the amplifier receives its
operating current from the loop that represents the
current output signal.
The loop has to be powered with a power supply or active
receiver capable of providing a voltage between 12 and
30 Volt @ 100 Ohm "loop resistance". When later on the
current is to be transformed to a voltage, it is important to
select the power supply voltage in accordance with the
desired output voltage.
Example:
Required voltage over the CT 24 is 10 Volt
(minimum value)
Required voltage over the 500 Ohm resistor
is 10 Volt (@ 20mA)
This implies that the supplied voltage has to
be at least 10+10 = 20 Volt.
Be aware that an active sensor (with some electronics)
can generally not be powered together with its CT 24 by
the same power supply. In that case the sensor output is
normally connected with the common of the power supply
and consequently also with the CT 24 output LO. This is
against the rule of thumb.
14
CONNECTION OF THE CT24
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