Connecting A Compensating Box For Thermal E.m.f. Measurement - Siemens S5-155U System Manual

9.3.9
Connecting a
Compensating Box for
Thermal E.M.F.
Measurement
Terminal Box
Thermocouple
+
Compen-
sating
Box
-
=
Power
Supply
for Com-
pensating
~
Box
Figure 9-8 Connecting a Compensating Box
System Manual
C79000-B8576-C109-03
If the room temperature fluctuations at the reference point (e.g. in the
terminal box) affect the measurement result and you do not wish to
use a thermostat, you can compensate for the effect of temperature on
the reference point with a compensating box. Between - 10 and
o
+ 70 C, it compensates for the change in thermal e.m.f. cause by
temperature deviation (compensating box, see Catalog MP 11). Ensure
that the compensating box has thermal contact with the terminals.
If the compensating box is aligned at 20
account in temperature evaluation (20
= 0 mV).
Pins 22 and 23 are extended on analog input modules as an input for
the compensating voltage. You must select a common input loop for
all inputs on mode switch 2.
The compensating box must be connected in a floating circuit. The
power supply unit of the compensating box must have a grounded
shield winding to avoid AC system interference being picked up. A
separate compensating box with its special power supply unit is
required for each analog input module.
M +
Range
Card for
M -
4 Inputs
6ES5 498-
-1AA11
22 +
23 -
The 460 Analog Input Module
o
C, this must be taken into
o
C measuring point temperature
Analog Input Module
A
MUX
#
D
0 V Bus
9 - 21
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