How does a belt weigher work? A belt weigher, also called a weightometer or conveyor belt scale, works by measuring the load carried across a short section of moving conveyor belt and combining that with the speed of the belt. Instead of stopping the process to weigh separate batches, it produces a continuous flow rate and a running total while the conveyor keeps running.
This guide explains the main parts of a belt weighing system, how the load and speed signals are combined into a tonnage figure, and why installation, condition and calibration all affect the number shown on the display.
- A belt weigher measures material continuously while the conveyor is running, rather than weighing separate batches.
- The weigh frame and load cells sense the load carried across a defined weighing section of the belt.
- A belt speed sensor provides the reference for how quickly that material is travelling.
- The integrator, or belt scale controller, combines the load and speed signals to produce a flow rate, commonly in tonnes per hour, and a running total, commonly in tonnes.
- Conveyor condition, installation, cleanliness, mechanical alignment and calibration all influence the result.
What does a belt weigher measure?
A belt weigher measures material while the conveyor is operating. Rather than weighing a fixed quantity, it estimates the mass moving through the weighing area over time.
The integrator uses two main measurements:
- The load applied by the material to the weighing section.
- The linear speed of the conveyor belt.
The integrator processes these two signals together to produce an instantaneous flow rate, usually in tonnes per hour, and a total amount of material moved, usually in tonnes. The available units and the information displayed depend on the equipment and how it has been configured.
What are the main parts of a belt weigher?
Most continuous belt weighing systems use the same broad building blocks, although the mechanical design varies between manufacturers and models.
Weigh frame or scale assembly
The weigh frame supports one or more conveyor idlers in the scale area. It transfers the relevant vertical force to the load cells while limiting unwanted forces from the conveyor structure, belt tension and material movement.
In practice, frame design varies between equipment types. Some systems use a floating frame, while others use pivots, flexures or different load cell arrangements.
Load cells
Load cells detect the force applied to the weighing assembly. Their electrical output changes as the load on the scale section changes, and the integrator processes that signal as part of the flow calculation.
Load cells are sensitive instruments. Mechanical damage, corrosion, incorrect wiring, material build-up, excessive side forces and changes in the supporting structure can all affect the measurement.
Weigh idlers and rollers
The idlers in the weighing area are part of the measurement system, not just belt support. They need to run in suitable condition and line up correctly with the approach and retreat idlers either side of the scale.
Similarly, misaligned, damaged, eccentric or inconsistent rollers can change how the belt passes through the scale area. Build-up around the rollers or weigh frame can also introduce unwanted forces.
Belt speed sensor
The belt speed sensor provides the reference used to determine how quickly material is moving through the weighing area. Depending on the system, this may be a contact sensor, spiral cage assembly, magnetic pickup, encoder, proximity sensor or another approved speed reference.
As a result, a speed sensor that slips, wears, loses contact, becomes obstructed or produces an unreliable signal can cause the calculated rate and total to be incorrect, even when the load cells are working correctly. Our guide on why belt speed matters to a belt weigher covers the speed reference in more detail.
Integrator or controller
The integrator, sometimes called the belt scale controller, receives the load and speed signals, processes them, displays the result, and can provide outputs to a control system, plant monitoring system or reporting application.
Available outputs can include analogue signals, totalising pulses, digital inputs and outputs, and communications interfaces. The exact options depend on the controller and the configuration.
How does a belt weigher work out the tonnage?
In general terms, the weighing section represents a known length of belt. The load sensed across that section corresponds to a mass for each unit of belt length. When that figure is combined with the measured belt travel, the result is a rate of material passing the scale, and accumulating those results over time produces a total.
The practical detail varies between systems. Sampling, filtering, zero and span settings, speed inputs and the way the controller displays or transmits results all depend on the equipment and its configuration. Refer to the manufacturer instructions for a specific integrator, or ask us about the system installed at your site.
This also explains why a fault in either input matters. For example, if build-up or mechanical interference affects the load signal, or the speed reference does not represent the real belt speed, the total can be wrong even though the equipment appears to be running normally. A related example is covered in our guide on why a belt weigher can read tonnes on an empty belt.
Why does installation affect the reading?
A belt weigher measures a moving conveyor system, so the surrounding conditions matter. Vibration, structural movement, belt tracking, belt tension changes, material surges, spillage and mechanical misalignment can all influence the measurement.
Keep the scale area mechanically stable and clear of avoidable interference, and position it so the belt travels consistently across the weighing idlers. However, the suitable location depends on the conveyor design, loading arrangement, material, belt behaviour and the required result, so a site assessment should confirm the final position. Our guide on where a belt weigher should be installed on a conveyor covers this in more detail.
Why do maintenance and calibration matter?
Routine service helps identify conditions that affect readings before they become larger faults. A service visit may include planning with the site, completing inductions, inspecting and cleaning the scale area, checking components, inspecting the speed reference, checking alignment, repairing defects where authorised, recording findings and carrying out calibration checks. Our guide on what happens during a belt weigher calibration visit explains the process.
Inspection, cleaning, adjustment, repair and calibration work often takes place around a conveyor. This work may require isolation, site induction, permits, authorised personnel and compliance with your site safety procedures. Do not reach into a conveyor, remove guards or work on electrical equipment unless you are trained, authorised and following those procedures.
For Accurate Industries belt weighers, the only grease points are the billet weight bearings and the spiral cage or speed sensor bearings, where fitted. There are no other grease points on the belt weigher. Other manufacturers set their own lubrication requirements, so follow the instructions for the equipment installed.
Carry out calibration checks using a method appropriate to the equipment, application and required level of measurement control. A maintenance calibration is not automatically the same as verification for legal for trade use. Where trade measurement requirements apply, confirm the applicable requirements with the relevant qualified or licensed personnel, or with the National Measurement Institute.
We can also retain service and calibration records against the relevant asset in AIMM, the Accurate Industries Maintenance Manager, where this is included in the service arrangement.
Can Accurate Industries work on a belt weigher we did not supply?
We manufacture our own belt weighers and weightometers and also support selected third party and legacy equipment, subject to the equipment and site requirements. This can include inspection, fault finding, calibration support, repairs, replacement components, service and spares, and ongoing maintenance.
Some integrators and controllers use passwords or access levels to prevent accidental changes to calibration, configuration or operating settings. Contact Accurate Industries if authorised assistance or access is required.
When should a belt weigher be inspected?
Consider arranging an inspection when:
- readings appear inconsistent or drift over time;
- totals do not match expected production or downstream figures;
- the belt speed signal appears unreliable;
- material has accumulated in or around the scale area;
- rollers, bearings or the weigh frame appear damaged;
- the belt is tracking poorly or the take up has moved; or
- the conveyor or the weighing equipment has recently been moved or modified.
In most cases, a technician can help determine whether the issue relates to the weighing assembly, load cells, belt speed reference, conveyor mechanics, material flow, controller configuration or another part of the application. Recording what the integrator is displaying, along with any fault messages and recent site work, usually shortens the investigation. Our guide on what should be checked before a belt weigher calibration lists what a technician looks at first.
Frequently asked questions
Is a belt weigher the same as a weightometer?
In Australian industry, people commonly use belt weigher, weightometer, conveyor belt scale and belt scale for similar continuous weighing systems. The equipment and terminology can vary between sites and manufacturers.
Does a belt weigher weigh the whole conveyor belt?
No. The weighing assembly measures the load that a defined section of the moving belt carries. The system then uses the belt speed reference to calculate the material flow and total.
Can a belt weigher be accurate if the rollers are misaligned?
Misalignment can affect the forces transferred through the weighing area and the way the belt travels across the rollers. Because of this, inspect and align the scale area as part of installation and service.
What is the difference between the flow rate and the total?
The flow rate describes how much material is passing the scale at a point in time, commonly in tonnes per hour. The total is the accumulated quantity that has passed the scale, commonly in tonnes, and it is usually the figure sites use for production reporting.
Who can service a belt weigher?
The appropriate service provider depends on the equipment, application and work required. Accurate Industries can assess and support its own systems and selected third party or legacy belt weighers.
Need help with a belt weigher?
We can assist with belt weigher assessment, supply, installation, commissioning, calibration, repairs and ongoing service. Contact the team with the equipment details, the conveyor application and the symptoms you are seeing, and we can advise on a practical next step.