User manual - METER SRT-457
Figure 4.8. Example of OC-type outputs connection
Temperature sensor can be connected to the device in typical 4-wire circuit (Figure 4.9a) or
3-wire circuit (Figure 4.9b). Due to precision of measurement 4-wire circuit is recommended.
If 2 wire circuit is used it is recommended to connect sensor accordingly to Figure
4.9c
.
(4-wires circuit with shorted pins 12+13 and 14+15). In this case, the
resistance of wires should be as small as possible, to avoid of measurement errors.
Measured value can be corrected (constant correction) using
toFS
parameter from
menu
inPt
. Due to low precision 2-wire connection is not recommended.
When 4-wires or 2-wires connection is used, the resistance of particular wires (Ra ÷ Rd)
CAN BE DIFFERENT
. When 3-wires connection is used, the resistance of particular wires
(Ra ÷ Rd)
MUST BE IDENTICAL
to enable proper compensation of it's resistance. The
resistance of particular wire
should not be greater than 20
Ω
Ω
.
a)
b)
c)
Figure 4.9. Connection of sensors:
a) 4-wires circuit; b) 3-wires circuit; c) 2-wires circuit;
The connection circuit should not be changed while unit is powered. Every change
of connection while the unit is powered causes measurement errors by several
seconds after change.
11
+
-
10 11
Uo
3 4
OC1
-
+
+
-
voltage input
24 V
Logic controller
10 11
Uo
3 4
OC1
-
+
+
-
R
2k2
LED 10 mA
Pt100
Ra
Rb
Rc
Rd
Ra, Rb, Rc, Rd can be different
12 13 14 15
Pt100
Rb
Rc
Rd
13
15
14
12
Rb = Rc = Rd
n.c.
Pt100
Rb
Rc
13 14
12
15
Rb, Rc can be different
i
i
