How to Calibrate a GX-1-20K-LE Floor Scale: Corner Trim, Zero & Span

pete8781
Jul 30
3 min read

For calibration questions or help matching a replacement load cell, call MNM Scales at (832) 290-3120 or email mnmscales@yahoo.com.

How to Calibrate a GX-1-20K-LE Floor Scale: Corner Trim, Zero & Span

Calibrating a weighing system after installing an MNM GX-1-20K-LE requires more than pressing a calibration key: first make the structure mechanically repeatable, then balance multiple load cells, then set zero and span with known reference loads.

1. Make the scale mechanically correct first

Unload the scale and inspect every load point. The deck or vessel should not touch guards, ramps, piping, conduits or adjacent structures. All supports should sit firmly, fasteners should be secure, and each load cell should be aligned so force enters through its intended loading axis. Electronic calibration cannot compensate reliably for a frame that binds or rocks.

2. Verify wiring and unloaded signal

MNM lists red as +excitation, black as -excitation, green as +signal and white as -signal for the GX-1-20K-LE. Confirm every junction-box terminal and connector before energizing. With the structure unloaded, the displayed weight should settle and return close to the same zero after a small load is applied and removed.

3. Perform corner testing before span calibration

On a four-cell platform, place the same test load near each load point in sequence and record the reading. If one corner differs materially, first correct leveling, binding and mechanical contact. Only after the mechanics are sound should you adjust junction-box trim. Repeat the corner test until readings are acceptably consistent for the intended accuracy class and service.

4. Set zero with the normal dead load in place

The indicator should be zeroed with the permanent deck, vessel, mounts and normal fixed hardware installed. Do not zero away temporary fixtures that will later be removed, because doing so changes the measurement reference.

5. Apply a known span load

Use certified test weights or another traceable reference load appropriate to the completed scale. A larger fraction of working capacity generally gives a stronger span calibration than a very small test load, provided the reference method and structure are safe. Enter the indicator's calibration mode according to its own manual, apply the known load, and store the span value only after the display is stable.

6. Verify multiple points and repeatability

After calibration, check zero, a low point, a mid-range point and a higher point if practical. Repeat at least one test load several times and confirm the scale returns to zero after unloading. Recheck corners because span adjustment and mechanical settling can expose new corner differences.

When calibration problems point to mechanics instead of electronics

One corner always reads high or low: inspect support height, foot movement, deck contact and junction-box trim.
Readings climb slowly under a constant load: inspect mechanical creep, damaged cabling, moisture and thermal effects.
Good at one test weight but poor elsewhere: verify the reference load, indicator configuration, linearity and whether the structure is deflecting into another object.
Zero shifts after forklift or impact events: inspect mounts and overload damage before simply recalibrating.

Comparable technical reference

For a comparable four-cell floor-scale workflow, see the Rice Lake Summit 3000 installation manual (PDF). It is not the GX-1-20K-LE manual, but it is a useful reference for leveling, corner testing, trimming and calibration sequence.

Calibration FAQ

Do I calibrate the load cell or the indicator?

In normal weighing service you calibrate the complete system through the indicator or transmitter while the installed load cells and mechanics are under known loads.