OHAUS CKW3R, Service Manual

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CHAPTER 2 DIAGNOSTIC GUIDE
2.1 TROUBLESHOOTING
This section of the manual provides guidelines for evaluating the condition and performance of a
Base unit, and a standard troubleshooting methodology to follow.
2.1.1 Checking Load Cells for Trouble
1. Visual Check:
– Remove any shipping material from between the upper and lower Housings, if
present.
– Clean the unit before evaluating any mechanical problems. In some cases,
debris may have accumulated inside the Base Housing. Make sure there is no
buildup of any foreign material.
– Examine the Base Housing for dents, bent Platform or signs of physical abuse
that could cause the Base to malfunction. Make sure that the proper Platform is
supplied with the Base. Replace all damaged parts. See Chapter 5 for parts
identification.
– Remove the Platform from the Base. Check that the Down Stops are not
touching the Top Plate. (See Figure 5-1, Chapter 5.) This would restrict
movement, causing improper operation of the Base. If the Down Stops are
improperly set, adjust them. (See Section 3.3.)
– Check the metal surfaces of the Platform. All surfaces should be parallel.
If the platform is deformed, it should be replaced.
– Check the cables leading to the Load Cell for cuts, abrasions or other signs of
excessive wear and tear.
– Check for a bent or twisted Load Cell: Place the top surface and then each of
the sides of the Load Cell on a flat surface, to see if it rests flat and even. A gap
indicates a bent or twisted Load Cell.
– Examine the Load Cell for corrosion due to high humidity or exposure to
chemicals.
– A Load Cell that is even slightly bent or corroded should be replaced.
2. Perform a Resistance Test , to determine if the Load Cell is severely damaged or a
short circuit to the frame has occurred. (See Chapter 4 for details.)
3. Perform an Output Voltage Test : Measure the no load, 50% load and full load
output. The reading should meet the Load Cell specifications. (See Chapter 4.)
– The Load Cell output should be very close to linear over its capacity range.
CKW Base Series Service Manual 2-1 Ohaus Corporation www.ohaus.com