Datcon DT9502 Operating Instructions Manual page 8

Operating principles
Power supply
8
It contains two limit outputs with selectable operating
modes, therefore it is suitable for simple control operations
too (e.g. temperature regulation).
Due to the function of DT9502 it can be placed in zone 1,
zone 2. The temperature sensor can be in zone 0 too.
A current generator (800 A) is connected to the terminal
pair PI+ and PI-.
In the case of four-wire measurements, the instrument
measures the voltage appearing in the terminal pair Pt+ and
Pt-. This solution ensures that the resistances of the lines
and contacts do not influence the measurement.
In the case of three-wire measurements, the line Pt+ is not
in use. The voltage between Pt- and PI- is deducted from
the voltage between PI+ and Pt-. This way when the
resistances of PI- and PI+ lines are identical with each
other, the voltage dropping in these lines does not influence
the accuracy of the measurement.
A built-in microprocessor is used to calculate the
temperature values. The results are presented on a 4-and-
half-digit LCD display. The limit outputs work in accordance
with the displayed temperature values.
The 4–20 mA current of the transmitter output could be
assigned to any temperature range. This way the best
possible settings could be achieved for a given application.
By press-buttons located on the front panel, the
temperature values assigned to the 4 mA transmitter current
and to the 20 mA current could be selected separately.
The apparatus has a „sink" type output, requiring external
power supply. This current ensures, at the same time, the
power supply for the apparatus too, and thus the device
connects to the receiving unit by two wires (+I, -I).
There should be minimum 12 V voltage on the terminals of
the apparatus.
DT9502
20171205-V3