How to Calibrate the MNM LP7515 / Optima OP-902 Indicator

pete8781
Jul 29
2 min read

For calibration assistance, call MNM Scales at (832) 290-3120 or email mnmscales@yahoo.com. MNM's product listing states calibration instructions are included.

To calibrate an MNM LP7515 / Optima OP-902 indicator, first confirm the connected load cell or platform is mechanically stable and wired correctly. The OP-902 manual used for this replacement family provides a documented calibration sequence with unit selection, preset or custom full-scale settings, no-load zero and add-load span calibration.

Before Entering Calibration

Place the scale on a stable surface, inspect the cable and connector, remove unwanted load, and let the electronics warm up. The OP-902 documentation recommends powering on for about five minutes before accurate weighing. If a floor scale has multiple cells, complete corner balancing first or verify that corner readings are reasonably matched before final span calibration.

Enter Calibration Mode

With the indicator off, the OP-902 manual instructs the user to hold HOLD and UNIT while powering on during the startup count. The display enters CAL kg; press UNIT to switch to CAL lb if needed, then HOLD to confirm. The display then presents an FS capacity selection.

Preset Capacity or FS6 Custom Setup

For standard ranges, select the appropriate FS value. For custom applications, FS6 allows the user to set decimal places, display division, maximum capacity and calibration loading weight. This is important for replacement-indicator work because the same LP7515/OP-902 family may be installed on many different capacities and readability combinations.

No-Load Zero Calibration

When the display reaches CALon, enter calibration. At noLoAd, make sure the scale has no applied calibration load and is stable, then press HOLD to capture zero. Permanent platform dead load is normal; what matters is that the platform is in its normal unloaded operating condition.

Add-Load Span Calibration

At AdLoAd, apply the calibration weight defined during setup. Wait for stability and confirm. The manual shows CALEnd when calibration is complete; save the result and return to weighing mode. For custom high-capacity systems, use a known load large enough to produce meaningful span. The manual’s troubleshooting guidance notes a minimum calibration weight requirement and recommends a substantially larger percentage of capacity when practical.

Verify After Calibration

Return to zero and test multiple known values, not only the calibration point. Check repeatability and, for multi-cell platforms, corner response. If the indicator is correct at one point but wrong at others, inspect mechanics, cell condition and configuration before simply repeating calibration.

Common Calibration Errors

The OP-902 manual associates overload/connection issues with UUUUUU or nnnnnnn, poor calibration or load-cell connection problems with ERR1, invalid calibration-weight range with ERR2, negative calibration signal with ERR3, unstable calibration signal with ERR4, and EEPROM problems with ERR5. If the signal is unstable, check wiring and load-cell mechanics before retrying.

Manual

View Optima OP-902 Indicator User Manual / Calibration Reference

FAQ

Why does the indicator say ERR2 during calibration?

The OP-902 manual indicates the calibration weight is outside the allowed range or below the minimum required. Check the configured capacity and calibration loading weight.