How to Calibrate the LP7515 Indicator (Optima OP-902 Replacement): Floor Scale Setup Guide

This guide shows how to calibrate the LP7515 indicator on a floor scale, step by step. The MNM Scales LP7515, our replacement for the Optima OP-902, is on sale for $99.00 (regular $199.00), in stock.

The MNM Scales LP7515 is one of the most popular indicators we sell. It’s a compact LCD weighing indicator used on floor scales, pallet scales, livestock and chute scales and bench bases, and many customers install it as a direct replacement for the Optima OP-902. After you install a new indicator, swap a cable or move the scale, you need to calibrate it. This guide follows the LP7515 manual step by step and adds the field tips our technicians use on floor-scale jobs.

Before you start

• Check the connection. The LP7515 drives up to four 350 Ω load cells. Make sure the platform cable is fully seated in the indicator’s quick-disconnect connector, and that a 4-pin or 5-pin connector matches your scale.
• Level and clear the platform. Set the scale on a flat, solid floor. Make sure nothing touches the platform frame, such as walls, pallets or debris under the deck.
• Warm it up. The manual recommends powering the indicator on about 5 minutes before weighing. Running it on the AC adapter avoids low-battery shutdowns in the middle of calibration.
• Have the right test weight ready. The weight must be at least 10% of the scale’s capacity, and the manual recommends 60 to 80% of capacity for the best result. For a 1,000 lb floor scale, that means roughly 600 to 800 lb of certified test weights.

Step 1: enter calibration mode and choose units

1. Turn the indicator off.
2. Press and hold HOLD and UNIT together while you power it back on, during the startup countdown.
3. The display shows CAL kg. Press UNIT to switch to CAL lb if you weigh in pounds.
4. Press HOLD to confirm.

Step 2: set the capacity (FS)

Next, the display shows a capacity code. The factory default is usually FS 5. Press UNIT to step through the presets, then HOLD to confirm. Each preset sets the capacity, the division and the calibration weight the indicator expects:

Code	kg mode: capacity / division / cal. weight	lb mode: capacity / division / cal. weight
FS 0	15 kg / 0.005 kg / 10 kg	33 lb / 0.01 lb / 22.05 lb
FS 1	30 kg / 0.01 kg / 25 kg	66 lb / 0.02 lb / 55.12 lb
FS 2	60 kg / 0.02 kg / 50 kg	132 lb / 0.05 lb / 110.25 lb
FS 3	100 kg / 0.02 kg / 75 kg	220 lb / 0.05 lb / 165.35 lb
FS 4	150 kg / 0.05 kg / 100 kg	330 lb / 0.1 lb / 220.5 lb
FS 5	200 kg / 0.05 kg / 150 kg	440 lb / 0.1 lb / 330.7 lb
FS 6	Custom: you set the decimal point, division, capacity and calibration weight (used for most floor scales)

Custom setup (FS 6) for floor and pallet scales

Floor scales of 1,000 lb and up use FS 6. In the setup menus, HOLD confirms, ZERO moves the cursor left, and UNIT changes the digit.

• dP: the number of decimal places, for example dP 0 for a 5,000 × 1 lb scale.
• d: the division (count-by), for example 1, 2 or 5.
• CAP: maximum capacity. Press HOLD to show the current value, edit it, then press HOLD.
• LoAd: the calibration weight you’ll actually place on the scale. Enter the exact certified total, then press HOLD.

Tip: the indicator displays up to 1/15,000 resolution, but a realistic division for a floor scale is usually capacity ÷ 5,000 or coarser (for example 5,000 × 1 lb or 10,000 × 2 lb). Setting the division too fine makes the last digit wander.

Step 3: zero and span calibration

1. At CALon, press HOLD to start weight calibration (or ON/OFF to exit without changes).
2. At noLoAd, make sure the platform is completely empty and press HOLD to capture zero.
3. At AdLoAd, place the calibration weight. On a floor scale, spread it evenly or center it. Wait until the reading is stable, then press HOLD.
4. When CALEnd appears, press HOLD to save, then ON/OFF to return to weighing.

Step 4: verify, including the corners

Remove the weight, confirm the scale returns to zero, and weigh the test weight again. Then do a quick shift (corner) test: put a smaller test weight over each corner in turn. If one corner reads noticeably different from the others, the cause is usually a damaged load cell, a bad cable or debris under that corner, not the indicator. Call us before you recalibrate around it. If a cell needs replacing, our load cell buying guide explains how to match the type and capacity, and our replacement load cells are quoted by phone at (832) 290-3120.

LP7515 error codes and what to do

Display	Meaning	What to do
UUUUUU	Overload, wrong load-cell connection or a load-cell problem	Remove weight, then check the connector and cable. Inspect the load cell’s input and output.
nnnnnn	Calibration off, wrong connection or a load-cell problem	Level the scale, check the connection and load-cell resistance, then recalibrate
ERR1	Calibration weight not placed, or above the set capacity	Use the correct weight within the capacity you set
ERR2	Calibration weight below the minimum (10% of capacity)	Use more weight, ideally 60 to 80% of capacity
ERR3	Negative signal during calibration	Check all wiring and the load cells, then recalibrate. If it persists, the board needs service
ERR4	Unstable signal during calibration	Wait for the platform to settle, remove vibration sources and start again
ERR5	Memory (EEPROM) error	The board needs replacement. Replacing the whole indicator is usually the fastest fix

Useful settings after calibration

Press HOLD + TARE together in weighing mode to open the user parameter menu. In the menu, HOLD confirms, ZERO moves left, TARE moves down and ON/OFF exits; the communication settings follow the user settings. Settings worth knowing:

• Hold: 0 = hold off, 1 = peak hold (pull and tension tests; press HOLD again to release), 2 = data hold (press HOLD to keep the current weight) and 3 = auto hold (keeps the stable weight automatically). Ht sets when a data or auto hold releases on its own: 0 = no time limit, 1 to 4 = 15, 30, 45 or 60 seconds; pressing HOLD also releases it.
• OFF: auto power-off after 10, 30 or 60 minutes, or off (0). BL: backlight off, on when weight changes, or always on.
• trn and bAud: RS-232 output. 0 = off, 1 = continuous sending to a PC, 2 = manual sending to a printer or PC (press TARE for 1 second to send), 3 = command mode (the PC sends “R”). bAud 1 = 9600 (default), 2 = 4800, 3 = 2400, 4 = 1200, 5 = 600.

Replacing an Optima OP-902 with the LP7515

Match the connector on your scale’s home-run cable, then pick the matching indicator:

• MNM Scales LP7515 Bright LCD Indicator (replacement for the Optima OP-902): our best-selling indicator
• MNM Scales LP7515 with 5-pin connector
• MNM Scales OP-902 readout with 5-prong connector, RS-232 and cable
• Cables: 15 ft replacement cable for the OP-902 / LP7515 and 15 ft 5-pin to bare-wire cable
• Power: 6 V AC adapter for the OP-902 / LP7515

Not sure which connector you have? Send us a photo of the plug and the scale’s data plate and we’ll match it. A new indicator must always be calibrated to the platform it’s connected to.

Let our technicians calibrate your floor scale

Floor scales need hundreds or thousands of pounds of certified weight to calibrate properly, so most businesses have us do it. MNM Scales is TDA licensed with registered technicians. Our technicians bring their own test weights for on-site floor scale calibration, so you don’t need to supply any; call to schedule. On-site service across the Houston area and suburbs is a $295 service call plus $2 per mile round trip, and Dallas, Austin and San Antonio are available on request. Same-day and emergency visits depend on availability, so call us. For smaller platform scales, you can ship them in for mail-in calibration (usually 1 to 3 business days).

• Bench scales over 6.2 kg up to 35 kg (about 14 to 77 lb): In-house calibration + certificate ($250) NIST calibration + certificate ($595)
• Scales over 35 kg up to 150 kg (about 77 to 330 lb): In-house calibration + certificate ($350) NIST calibration + certificate ($750)
• Floor scales over 150 kg (over about 330 lb): In-house calibration + certificate ($495) NIST calibration + certificate ($995)
• All prices and tiers: see how much scale calibration costs, or browse our floor scales and scale indicators.

MNM Scales has been in business for over 30 years and is one of the largest scale distributors in the country. We sell the indicator, the cables and the scale, and we install and calibrate them, so one call covers the whole job. Scale rentals are available while yours is being repaired. See our scale services.

Frequently asked questions

How do I get into calibration mode on the LP7515?

Turn the indicator off, then press and hold HOLD and UNIT together while it powers on and counts down. The display shows “CAL kg”. Press UNIT for lb, then HOLD to confirm.

How much weight do I need to calibrate a floor scale?

The LP7515 needs at least 10% of the scale’s capacity and recommends 60 to 80%. On a 1,000 lb floor scale that’s roughly 600 to 800 lb of certified test weights, which is why most businesses book on-site calibration. Our technicians bring the test weights, so you don’t need to supply any.

What does ERR2 mean on an LP7515?

The calibration weight was below the minimum, which is 10% of the capacity you set. Add more weight (ideally 60 to 80% of capacity) and repeat the calibration.

Can the LP7515 replace my Optima OP-902?

Yes. MNM Scales sells the LP7515 as a replacement for the OP-902, in 4-pin and 5-pin connector versions. Match the connector on your scale cable, then calibrate the new indicator to your platform.

How do I print from the LP7515?

Set the communication parameter (trn) to 2 for manual sending and match the baud rate to your printer (9600 by default). Then press TARE for 1 second to send the reading.

How do I set the LP7515 up for livestock weighing?

In the parameter menu, set Hold to 2 (data hold: press HOLD to keep the weight once the animal settles) or 3 (auto hold: the indicator keeps the stable weight on its own). Then set Ht for how long the reading stays: 0 = until you press HOLD again, 1 to 4 = 15 to 60 seconds.