Let me start with a real example.

A logistics company in Lusaka came to us with a problem. They'd bought a cheap 80-ton scale from a reseller – no name brand, no local support. After about 14 months, they noticed something odd.

Every morning, the first three trucks would weigh about 200 kg lighter than the same trucks weighed later in the day. Then by afternoon, the scale would drift again. They'd lose 150–300 kg per truck on some loads, gain on others.

Over a year, running 40 trucks a day, each carrying about 25 tons of copper concentrate… do the math.

That 200 kg drift is less than 1% error. But on a $4,000-per-ton product, 200 kg is $800. Multiply by 40 trucks – $32,000. Do that for 250 working days – that's $8 million of potential mis-weighing risk. Not all of it would be pure loss, but even a small fraction is enough to kill your margin.

Accuracy matters. And it's not just about the number on the certificate.

So, what's a realistic accuracy for a good weighbridge?

A properly installed, OIML-certified 80-ton scale should give you:

- ±0.1% of the load under ideal conditions (flat, clean, calm)

- ±0.2–0.3% in real-world African conditions (slight slope, dust, daily temperature swing)

That means on a 40-ton truck, you can expect a reading within about 40–120 kg of true weight. Anything worse than ±0.5% – that's 200 kg error on 40 tons – means something is wrong.

Cheap scales with low-quality load cells often drift to ±1% after a year. That's 400 kg error on a 40-ton truck. On bulk commodities like cement, grain, or fuel, that adds up fast.

What affects accuracy day to day?

From our installations across Africa, here are the biggest culprits:

1. Temperature changes – Load cells contain strain gauges and electronics. Cheap cells have poor temperature compensation. Morning vs afternoon can shift readings by 0.2–0.3% on a hot day. We've seen it happen in Kenya's Rift Valley – 15°C at dawn, 35°C at noon. That's enough to cause disputes with suppliers.

2. Dirt and debris under the deck – A surface-mounted scale sits on steel beams. Mud, rocks, or spilled material can pile up underneath, pushing up on the deck and creating false weight. We've cleaned out 200 kg of mud from under a scale that hadn't been hosed in six months. Guess what – after cleaning, the scale read 200 kg lighter. The client had been overpaying suppliers for months.

3. Uneven ground settlement – Concrete foundations settle over time, especially on soft soil. If one corner drops by just 5 mm, the load distribution changes and readings become inconsistent. Regular foundation checks are free and take 10 minutes.

4. Lightning and power surges – In thunderstorm-heavy regions like Zambia's Copperbelt, a nearby strike can scramble the indicator's internal calibration without you noticing. We recommend surge protection on every installation.

How often should you calibrate?

There's no universal answer, but here's a rule of thumb based on traffic volume and environment:

But here's the practical advice we give our customers:

Don't just rely on a calendar. Set up a simple monthly check using a test truck.

Here's how:

- Pick one truck that you weigh regularly. Same truck, same load type (e.g., always about 70% full).

- Weigh it first thing in the morning, same day each month.

- Write down the weight.

- If it changes by more than 0.3% from the previous month – or more than 0.5% from the original calibration – call for a service check.

It's free, takes five minutes, and catches drift early. Many of our clients in Kenya and Tanzania use this method between professional calibrations.

What does professional calibration actually involve?

A technician brings certified test weights – usually metal blocks of known mass, totalling at least 50% of the scale's capacity (e.g., 40 tons for an 80-ton scale). They place these weights in different positions (center, corners, edges) and adjust the indicator until the reading matches the known weight.

Cost varies by country and travel distance, but expect roughly:

- Local tech in major city: $300–$600 per visit

- Travel to remote mine or farm: $800–$1,500 (including transport and overnight stay)

Most good suppliers offer calibration as part of a maintenance contract. At Fangda, we provide calibration guidance for clients who have local metrology technicians, and we can arrange professional calibration through our partner network in Zambia, Kenya, and Tanzania.

What about digital weighbridges with RFID – do they need different calibration?

No, the scale itself works the same way. The RFID system just identifies the truck and driver. But one advantage of a digital weighbridge with RFID is that you can track weight data per vehicle over time. If Truck A always reads 100 kg heavier than Truck B with the same product, you might have a calibration issue – or you might have a driver who knows how to cheat the scale (e.g., parking with one wheel off the deck). The data tells you to investigate.

A quick story from a Tanzanian farm cooperative

They had a portable 60-ton scale for cotton. They calibrated it once when new, then never again for two years. By the end of the second harvest, they noticed disputes with farmers – each farmer claimed their trailer weighed less at the co-op than at a neighboring buyer's scale.

We tested it with a rented set of weights. The scale was under-reading by 1.2% – about 300 kg on a 25-ton load. Over 2,000 loads that season, that's 600 tons of unpaid cotton. At $500 per ton, that's $300,000 lost. All because they didn't spend $500 on a calibration check.

Bottom line:

A weighbridge is a measurement instrument, not just a piece of steel. If you don't verify its accuracy, you're trusting blind luck with your revenue.

Three simple rules:

1. Get an OIML-certified scale – it starts accurate.

2. Do a monthly test truck check – catch drift early.

3. Professionally calibrate at least once a year – more often for heavy use.

At Fujian Fangda Weighbridge Manufacturer, China, we build accurate scales. But accuracy doesn't last forever without maintenance. If you need help setting up a calibration schedule for your site – or want to know what to expect for calibration costs in your country – just ask. We've done it across Africa, and we know what works.

Fujian Fangda Weighing Instruments provides a full range of electronic weighbridge from 30 tons to 200 tons