Adam Equipment CBW 100a, Руководство по обслуживанию

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@Adam Equipment Company 2005 12
7.0 LOAD CELL DAMAGE
The most common reason a scale fails is that the load cell has been damaged. The
damage can be from 2 primary causes. The first is physical damage due to an
overload or an impact from the side and the second is damage due to the
environment, such as moisture, extreme heat or a cut cable if the cables are
exposed.
PRINCIPLE OF OPERATION
The stain gauge load cell is a method of measuring the amount of stress put onto a
metal structure due to a weight being supported by the structure. The stress is
measured using 4 strain gage sensors mounted in a particular way on the metal
structure.
These 4 strain gauges are connected in such a way that they form a wheatstone
bridge. See figure below. In the simplest load cells there are only the 4 resistances
of the strain gages to consider. Normally without a load on the load cell all the
resistances are the same. However when the load cell has a weight on it 2 of the
strain gages will be in compression (A and D) and the resistance will decrease and 2
will be in tension (B and C) and their resistance will increase.
350
oh
m
35
0 o
hm
350
oh
m
35
0 o
hm
A
B
C
D
+E
-S
-E
+S
BALANCED BRIDGE
10 VOLT POWER
SUPPLY
Vout = O VOLTS,
BS AND -s
351
oh
m
34
9 o
hm
351
oh
m
34
9 o
hm
A
B
C
D
+E
-S
-E
+S
UNBALANCED BRIDGE
FULL CAPACITY LOAD
ON THE LOAD CELL
10 VOLT POWER
SUPPLY
Vout = 0.028 VOLTS (28mv),
BS AND -s