19
DAQP-CFB2
Why use more wire technology
Sensitivity: For sensor wiring typically copper cables are used. For example a 120 Ω full bridge
connected with a 4 x 0.14 mm
2
cable will have an sensitivity error of 2.1 % just because of the 1.27 Ω
wire resistance. By using the 6 wire technology, this can be completely compensated.
Temperature drift: Copper has a temperature drift of 0.4 % /°C.This is especially a problem at quarter
bridges, because also the offset changes with the wire resistance. The following table shows the
difference between the 3 wiring methods for a 120 Ω strain gage with a 50 m cable 0.25 mm
2
.
Initial error
Drift because of 10 °C warm-up
Offset
Sensitivity
Offset
Sensitivity
2-wire
25183 µm/m
-4,97 %
956 µm/m
-0.18 %
3-wire
0 µm/m
-2.6 %
0 µm/m
-0.01 %
Cables
To keep the influence of electromagnetic disturbances as small as possible shielded twisted pair cables are
strongly recommended. Connect the shield to the GND or the housing (pin 4).
The twisted pairs for all bridge modes are:
EXC+ PIN1 and EXC- PIN8
Sense+ PIN6 and Sense- PIN3
IN+ PIN2 and
In –
PIN7
R + PIN5 and
GNDisolated PIN4
For quarter bridge mode the pairs are:
IN+ PIN2 and
Sense – PIN3
R + PIN5 and
EXC- Pin8
If TEDS is used it is recommended mounting the TEDS chip nearby the module. The ideal case would be if
the chip is mounted inside the D-SUB housing. The maximum distance between modules and TEDS chip is
20 m.
450134 • DAQP/H
SI
/PAD Modules • Technical Reference Manual • Prin
t
ing version 2.3.4 • November 18, 2020
Summary of Contents for DAQP-CFB2
Page 20: ...20 DAQP CFB2 Notes ...
Page 22: ...C2 NOTES ...
