Technical Guides

Load Cell Wiring Diagram & Installation Guide

A load cell wires to an indicator through four mandatory conductors — EXC+, EXC−, SIG+, SIG− — plus two optional sense conductors (SEN+, SEN−) on 6-wire cable for temperature and cable-length compensation. Correct wiring preserves the cell’s rated mV/V accuracy across its compensated temperature range; incorrect wiring introduces signal drift, ground loops, or full signal loss that calibration cannot recover.

This guide covers 4-wire and 6-wire configurations, industry wire color conventions, shield grounding best practice, and junction box summing for multi-cell platforms — with a step-by-step procedure for the single-cell indicator connection most integrators face first.

Key Takeaways

What You Need to Know

• 4-wire: use for cable runs under 15 ft in stable temperature environments
• 6-wire: use for runs over 15 ft, temperature-cycled installations, and high-accuracy applications — sense compensation eliminates ±0.02%/10 m temperature drift
• Shield grounding: ground the cable shield at the indicator end only — one-point grounding prevents 60 Hz ground loops
• Junction box: sums excitation in parallel and signals in series for multi-cell platforms; individual trim pots balance corner zero and span
• Color codes: red/black excitation, green/white signal, blue/yellow sense (industry standard — verify nameplate before termination)

Wiring Basics

Four Signals, Two Optional Senses

Every industrial load cell has a Wheatstone bridge of strain gauges wired to four external terminals. EXC+ and EXC− supply regulated DC excitation (typically 5V or 10V, depending on indicator specification). SIG+ and SIG− return the millivolt signal proportional to applied load — a 2.0 mV/V cell excited at 10V produces 20 mV full-scale; a 3.0 mV/V cell produces 30 mV. The indicator reads this differential signal and scales it to engineering units.

On 6-wire cable, SEN+ and SEN− add a voltage-feedback loop from the cell’s excitation terminals back to the indicator. The indicator measures the actual voltage arriving at the cell (after cable voltage drop) and adjusts its excitation supply to maintain the rated value. This sense compensation matters most on long cable runs and in temperature-cycled environments where copper resistance changes by 0.39% per °C. Without compensation, a 50 ft run of 22-gauge 4-wire cable can lose 0.05% of excitation voltage at 25°C — enough to shift zero and span in a precision weighing application covered by NIST Handbook 44 legal-for-trade tolerance limits.

Color Code Convention

Industry Standard Wire Colors

Industry-standard load cell cable uses a consistent color convention across most manufacturers, but verify the cell’s nameplate or datasheet before termination — some legacy cells and OEM-specific cable assemblies deviate. The table below shows the standard configuration used on Transcell cells and most major industry suppliers.

4-Wire vs 6-Wire

When to Use Each Configuration

Use 4-wire cable for runs under 15 ft in environments with stable ambient temperature (indoor, climate-controlled). 4-wire is lower-cost, simpler to terminate, and sufficient when cable voltage drop is negligible. Use 6-wire cable for runs over 15 ft, for any application crossing seasonal temperature swings, and for precision weighing where ±0.02% combined error matters. Sense compensation on 6-wire cable actively corrects for cable voltage drop and temperature-induced copper resistance change, preserving the cell’s rated accuracy across the full installation range.

Retrofit flexibility: if a 6-wire cell must connect through a legacy 4-wire cable, jumper SEN+ to EXC+ and SEN− to EXC− at the junction box or cell-side terminal block. This converts the 6-wire cell to non-compensated operation and works acceptably for runs under 25 ft in stable temperature. Do not use this jumper workaround on long runs or temperature-cycled installations — the drift will manifest as daily zero and span variation.

Field tip: never extend a 4-wire cable with a separately spliced 4-wire run. Every terminal block connection is a potential source of thermal EMF (different metals + temperature gradient = microvolt-level error signal) and resistance drift as the connection oxidizes. Pull a single continuous cable from cell to indicator, or if length requires, upgrade to a 6-wire cable and terminate both ends cleanly.

Step-by-Step Procedure

Wiring a Single Load Cell to an Indicator

The sequence below applies to a standard 4-wire or 6-wire installation from a Transcell load cell to any compatible weighing indicator. Total install time for an accessible cell: 20–40 minutes including initial zero and span calibration.

Step 1. Verify the Load Cell Nameplate

Confirm rated capacity, mV/V output (2.0 or 3.0), excitation voltage (typically 5V or 10V max), and bridge input resistance (350 Ω standard). Match the indicator’s expected cell configuration before wiring.

Step 2. Identify Indicator Terminal Block Labels

Locate EXC+, EXC−, SIG+, SIG− (and SEN+/SEN− if indicator supports 6-wire). Verify excitation voltage setting on the indicator matches what the cell is rated to accept.

Step 3. Strip and Prepare the Shielded Twisted-Pair Cable

Strip outer jacket back 3–4 inches. Strip individual conductor insulation 1/4 inch. Keep the drain wire (shield) separated and long enough to reach the shield terminal on the indicator only.

Step 4. Terminate Wires to Corresponding Terminals

Match wire color to signal per the color code table above. Use a torque screwdriver set to 0.5–0.8 N·m for terminal block screws. Verify each connection has no stray strands and no insulation caught under the clamp.

Step 5. Ground the Shield at the Indicator End Only

Connect the drain wire to the indicator’s shield terminal or ground lug. At the load cell end, trim the drain wire flush inside the cable gland and do not connect to cell ground. This one-point grounding aligns with IEC 61000-4 industrial EMC immunity practice and eliminates the 60 Hz ground loop that would otherwise inject noise into the signal.

Step 6. Power On and Calibrate

Apply indicator power with the load platform empty. Zero the indicator. Apply a known calibration weight (typically 50–100% of rated capacity), record indicator reading, span-calibrate. Record the final zero and span values in the install log for future drift comparison. For the full calibration workflow including dead-weight and substitution methods, see the load cell calibration procedure.

Junction Box Summing

Multi-Cell Platform Wiring

Multi-cell platforms — truck scales, large hoppers, conveyor weigh-stations, and any scale using 3 or more cells at the load-bearing corners — require a summing junction box to combine the individual cell signals into a single output for the indicator. The junction box parallels excitation across all cells (they all see the same EXC+ and EXC−) and sums the signal returns through a resistor network that produces a weighted average proportional to total load.

Critical wiring practice for summing junction boxes:

• Terminate each cell’s cable in its own dedicated position on the junction box terminal block — do not daisy-chain cells
• Balance each cell’s individual trim potentiometer (zero and span adjustments) during initial corner calibration — the scale should read the same test weight regardless of which corner it sits on
• Ground all cell shields to the junction box shield bus; run a single shielded cable from the junction box to the indicator with its shield grounded at the indicator end only
• Mount the junction box as close to the load cells as practical — short cell-to-JB cable runs minimize voltage drop before summing
• After any cell replacement in a multi-cell system, re-balance the trim pots — a drop-in replacement rarely matches the legacy cell’s exact zero and span within the junction box network

For Transcell-compatible summing junction boxes with 4, 6, 8, or 10-channel configurations in weatherproof IP65 housings, see junction box product options. For replacement shielded cable in standard and custom lengths, see load cell cable.

Troubleshooting

Common Wiring Failure Modes

The table below maps the most common wiring failure symptoms to likely causes and field fixes. For symptoms not listed or when multiple symptoms coincide, contact Transcell application engineering before swapping hardware — miswired installations occasionally present as apparent cell failure.

FAQ

Can I extend a 4-wire load cell cable with a spliced 4-wire run?

Not recommended. Every splice introduces thermal EMF from dissimilar metals at the terminal block, plus added resistance that drifts as the connection ages. For runs over 15 ft, pull a single continuous 6-wire cable from cell to indicator and terminate both ends cleanly. For short legacy extensions (under 5 ft), spliced 4-wire is acceptable only in temperature-stable indoor environments.

Do I ground the cable shield at both the cell end and the indicator end?

No. Ground the shield at the indicator end only. Grounding at both ends creates a ground loop — a circuit between the cell chassis and the indicator chassis through the shield itself — which injects 60 Hz AC hum into the low-level signal. One-point shield grounding is the industry-standard practice for every manufacturer of industrial weighing equipment.

What’s the difference between sense-compensated and non-compensated wiring?

Sense-compensated (6-wire) wiring uses two extra conductors to feed back the actual excitation voltage at the cell, letting the indicator adjust for cable voltage drop. Non-compensated (4-wire) wiring assumes the indicator’s excitation output equals the voltage at the cell — true only for short cables at stable temperature. Sense compensation eliminates ±0.02% per 10 m of cable-induced drift across the ambient temperature range.