Fault Self‑Diagnosis Library

Step 1: Visual & Mechanical Inspection

• • Check load cell body for dents, cracks, corrosion, bending.
• • Inspect cable for cuts, crushing, rodent damage, or poor sealing at entry point.
• • Verify mounting surfaces are clean, level, and flat.
• • Confirm no mechanical binding (pipes, structures, debris creating parallel load paths).
• • Check that support screws / shipping stops are properly loosened.
• • Look for product buildup under platforms or around modules.

Step 2: Electrical Tests (Multimeter)

• Zero Balance Test – Apply rated excitation voltage, measure signal output with no load. Compare to datasheet (usually within ±1%).
• Bridge Resistance Test – Measure Exc+ to Exc– and Sig+ to Sig–. Should match datasheet (typically 350 Ω or 700 Ω ± tolerance).
• Insulation / Leakage Resistance – Use megohmmeter (500 V DC). Measure between all wires and load cell body. Healthy reading: > 5,000 MΩ. Low = moisture.
• Cable Continuity & Shield Test – Check each conductor for continuity and shorts. Verify shield is not shorted to body.

Step 3: System‑Level Debugging

• • Isolate the load cell from the indicator/transmitter and test independently.
• • Test each load cell individually in multi‑cell systems (use junction box test points).
• • Check excitation voltage at the load cell (stable, typically 5–15 V).
• • Verify grounding: single‑point ground, no ground loops, proper shield termination.
• • Look for electrical noise sources (VFDs, motors, welding equipment).
• • Confirm indicator/transmitter settings (capacity, sensitivity, digital filtering).

Step 4: Functional / Load Test

• • Apply known certified weights and check linearity and repeatability.
• • Perform corner/section tests on multi‑cell platforms.
• • Check hysteresis (difference between loading and unloading readings).
• Quick Diagnostic Priority Order:
• 1. Visual & mechanical → 2. Cable integrity → 3. Insulation resistance → 4. Zero balance & bridge → 5. Indicator settings → 6. Full calibration check.

Preventive Maintenance Schedule

• Daily / Shift: Visual check for debris, damage, unusual readings; zero the scale.
• Weekly / Monthly: Inspect cables, junctions, mounting; clean platforms and modules.
• Quarterly: Check insulation resistance, verify zero stability, inspect for corrosion.
• Annually (or per legal requirements): Full calibration with traceable weights + documentation.
• After any event: Shock load, flooding, welding nearby, major mechanical work → inspect and recalibrate.

Key Maintenance Actions

• • Keep load cells and platforms clean and free of product buildup.
• • Protect cables (conduit, cable trays, proper strain relief).
• • Maintain proper sealing (cable glands, junction boxes).
• • Avoid overload and shock loading; install mechanical stops where possible.
• • Control environment (temperature, humidity, vibration) as much as practical.
• • Keep calibration certificates and maintenance logs up to date.

How Load Cells Work

A load cell converts mechanical force (weight, tension, compression, or shear) into a proportional electrical signal.

Core Principle (Strain‑Gauge Type):

• Elastic metal body deforms slightly under load (Hooke's Law).
• Foil strain gauges bonded to the body change resistance when stretched or compressed.
• Four gauges wired in a full Wheatstone bridge (two in tension, two in compression).
• No load = balanced bridge → near‑zero output.
• Under load = unbalanced bridge → differential voltage (1–3 mV/V of excitation).

Signal Chain: Raw mV → Amplification → ADC → Processing → Display / Output

Main Types of Load Cells

• Single‑point: Retail, bench, platform scales – off‑center load tolerance.
• S‑type / S‑beam: Hoppers, cranes – tension + compression, versatile.
• Single‑ended shear beam: Floor scales, tanks, conveyors – side‑load resistance.
• Double‑ended shear beam: Truck scales, large platforms – high capacity.
• Canister / column: Truck scales, silos, heavy tanks – very high capacity.
• Pancake / low‑profile: Presses, testing – low height, good off‑axis.
• Load pin: Cranes, sheaves, clevises – replaces existing pin.
• Button / miniature: Tight spaces, embedded – compact.
• Tension link: Suspended weighing, cable tension – inline mounting.

Training & Capacity Building

We deliver operator training scale, technician training mizan, and calibration training programmes for cooperatives, factories, and government agencies.

• • Operator training on digital indicators and printers
• • Technician training on load cell wiring and diagnostics
• • Calibration training for in‑house QA teams
• • EUDR compliance training for coffee cooperatives

Service Contracts & SLAs

Choose from a range of maintenance plans designed for Ethiopian industry:

• • Preventive maintenance contract (quarterly visits)
• • Annual service plan with test weight rental
• • SLA agreement with 24‑hour response time
• • Emergency callout and weekend service
• • Same day repair for critical production lines
• • 24/7 support for weighbridges on national corridors

Retrofitting & Modernization

We specialise in retrofitting scale, upgrade weighbridge, and modernization weighing. Our digital conversion mechanical scale service transforms legacy platforms into modern digital systems with remote monitoring.

Giveaway Audit & Loss Optimization

For flour mills, cement plants, and packaging lines, we deliver giveaway audit factory programmes, loss optimization, dosing tuning, batch tuning, and feed rate optimization. Typical savings: 2–3% of annual product value.