Warner Electric FM Series Foot Mounted Load Cells AC10 Measuring System A-B-C30 - Manual (Page 29)

29 Warner Electric • 800-825-9050 P-2012-3
C. The Electrical System
The electrical system consists of a Linear
Variable Differential Transformer (LVDT) which
converts the mechanical deflection of the Load
Plate into a useful electrical output signal. (See
Figure 3) The moveable core of the LVDT is
mechanically coupled to the Load Plate.
This core assemble is factory set and is not
accessible.
D. Type "K" DC LVDT
As illustrated in Figure 3, a DC LVDT consists of
the following components:
• An oscillator network, which converts the DC
input voltage into a high frequency alternat-
ing current for exciting the primary coil (P1)
• A Primary Coil (P1)
• A movable, permeable metallic core
• Two Secondary Coils (S1 and S2)
• A demodulator and summing network to rec-
tify and integrate the currents from the
Secondary Coils
Figure 3
Black - (2)
Red + (1)
Green (3)
Blue (4)
Input Output
X Twisted Leads
A B
Oscillator Demodulator
P1
S1
S2
X X
When Supplied
with Cable
(1) Red + DC
(2) Black – DC
(3) Green – Signal
(4) White + Signal
C D
B
A C
D
With Warner Electric LVDTs, the input and out-
put circuits are electrically isolated from each
other and from the mechanical structure of the
tensioncell. Thus, they may be used in "floating
ground" or "ground return" systems. This elimi-
nates the need for extra circuit boards which are
required for most straingage loadcells.
Tensioncells are factory adjusted to provide an
offset voltage with no load applied (no deflec-
tion). Using an input of 24 volts DC, the LVDT is
set to provide an output of 3.5 volts into a resis-
tive load of not less than 100,000 ohms. The
voltage resulting from the maximum rated
deflection then adds to or subtracts from the 3.5
volt offset. This results in an output voltage of
3.5 to 6.5 volts in the Compression Mode and
3.5 to 0.5 volts in the Tension Mode. (See
Figure 4)
While acceptable performance may be obtained
over an input voltage range of 6.0 to 30.0 volts
DC, the output voltage will vary in direct propor-
tion to the input voltage. Because of this, the
use of a well regulated constant voltage power
supply is essential for accurate and repeatable
tension measurement.
7
6
5
4
3
2
1
0
.030” 0.0 .030”
3.5 V. Set Point
Tension T T Compression ion
LVDT L L Output vs Deflection
O
u
t
p
u
t
V
o
l
t
a
g
e
Deflection
Figure 4
LVDT Output vs. Deflection Chart