Haemonetics SEBRA 1040, Service Manual

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5-4 Strain Gauge
P/N 108755-US, Manual revision: AA
5. Reference drawing 10402500. Remove weight sensor assembly from the
base. Mount assembly on bench with a c-clamp.
6. With an oscilloscope, attach the probe to Pin 1 on U1 and ground the
probe to R1 on the strain gauge PCBA. Plug in the Shaker.
7. Set the oscilloscope vertical input to AC mode and 1 volt per division cen-
tered on the display, horizontal input at 350 ms-14 ms to view output.
Warning: With the removal of the Body Board and Power Supply PCBA's from
the base, AC and DC voltages are exposed. Use CAUTION when handling these
assemblies.
Warning: Input Power fuse "F1" fuse holder, located on the power supply PCBA,
is exposed when the Body Board and Power Supply PCBA's are removed from
the base. Use CAUTION when handling this assembly.
Warning: Before applying AC power, connect AC ground from the input power
receptacle to the chassis plate ground stud.
8. Start Shaker weighing routine (crank arm must be attached for one-bit en-
coder to sense rotation).
9. With no load on knife edge, oscilloscope should show a maximum of 200
mv (see Figure 5-4, Oscilloscope Reading). If the reading is higher, verify
cage alignment and mounting screw torque and ensure strain gauge align-
ment freedom of movement. If problem still exists, contact Haemonetics
for strain gage replacement options.
Figure 5-4, Oscilloscope Reading
10. Gently press down on knife edge. The oscilloscope should show a signal
similar to the wave form in Figure 5-5, Oscilloscope Wave Form.