Eagle Microsystems LCWA-HI User Manual
Page 5
LC-WA HI IB.doc
9/16/04
SECTION 4.0 SERVICING
4.1 Checking the connections to the Summing Box.
1. Locate the Summing J Box and remove the lid.
2. View and compare all connections to Figure 2.
3. Check all connections by lightly pulling on each lead. Tighten terminal connections as
needed.
4. If problem persists, press lightly on the circuit board itself and check meter response.
Replace board if required.
Note: Make sure when replacing the cover that the box is dry and the cover is tight.
Figure 2: Summing Junction Board
4.2 Checking the load cells.
1. Load Cell resistance test:
a.
Disconnect the load cells from the Summing Box and measure the resistance as shown in
Figure 3.
b. Any electrical leakage between the leads and the load cell case is usually caused by moisture
leakage into the load cell or by moisture in a damaged load cell cable.
c. If a load cell does not pass the above resistance tests, replace it with a known good one.
2. Load Cell zero shift test:
a.
Remove all the weight from the load cell and measure the output as shown in
Figure 4.
b. Connect a DC power supply of 10 or 15 volts to the Red (+) and Black (-) excitation load cell
leads.
c.
The measured output between the Green (+) and White (-) signal leads should be less
than 5 millivolts.
d. An output signal greater than 5 millivolts indicates a zero shift caused by mechanical
overload.
e. If the output signal is between 5 and 15 millivolts, the load cells zero has shifted but will
probably still continue to work.
-EXCT
-SENS
+EXCT
+SENS
-SGNL
+SGNL
SHLD
-SGNL
+SGNL
SHLD
-SGNL
+SGNL
SHLD
-SGNL
+SGNL
SHLD
-SGNL
+SGNL
SHLD
+EXCT
+EXCT
+EXCT
+EXCT
-EXCT
-EXCT
-EXCT
-EXCT
INSTRUMENT