MNM Scales 4 x 2,500 lb Floor Scale Kit Calibration Guide: Corner Trim, Zero & Span
- pete8781
- Jul 29
- 2 min read
For scale-build or calibration help, call MNM Scales at (832) 290-3120 or email mnmscales@yahoo.com.
Calibrating a four-cell floor scale built with MNM 2,500 lb shear beams is a two-stage job: first make all four load points agree, then calibrate the combined system for zero and span. Trying to span-calibrate before correcting the corners can produce a scale that is accurate in the center but wrong when a pallet or load sits toward one side.
1. Inspect and Level the Mechanical Structure
Confirm all four feet contact the floor, the frame is not rocking, spacers are installed consistently and no load cell is twisted. Check for debris, binding, welded distortions or a ramp/guard contacting the deck. Mechanical instability must be corrected before touching junction-box trim pots.
2. Verify Wiring and Signal Direction
MNM lists red +excitation, black -excitation, green +signal and white -signal. Confirm each cell is landed consistently in the summing box. A reversed signal pair can make one corner subtract rather than add, and a loose excitation wire can create intermittent drift that no calibration will fix.
3. Corner-Trim the Junction Box
Place the same test load near each load-cell corner in turn. Record the displayed value. Use the summing-box trim adjustment to bring the high and low corners together, following the junction-box procedure used in your scale. Repeat the cycle until corner differences are acceptable for the intended application. Keep the test load position consistent from corner to corner.
4. Set Zero and Span at the Indicator
With the platform empty and stable, establish zero. Apply a known calibration load and perform span calibration using the indicator manufacturer's procedure. Use enough load to meaningfully exercise the system while remaining within the engineered platform capacity. The load used to calibrate the indicator is not the same thing as the sum of the four load-cell nameplates.
5. Verify Center, Corners and Repeatability
After span, repeat the corner test and check the center at several weights. Remove the test load and verify return to zero. If a corner changes after span calibration, revisit mechanical support and corner trim rather than repeatedly changing span. If one corner is unstable, inspect that cell and cable individually.
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