Create the dose
The multihead weigher distributes product, weighs portions and selects a permitted combination close to the target.
Direct answer
A multihead weigher creates the dose before packing; a checkweigher verifies the completed pack afterwards.
The multihead weigher controls product portions and releases a target dose into the packer. The checkweigher measures the finished pack, including tare variation and any transfer loss or addition. A line may use both systems, and some selected equipment can support feedback between them, but the interface and control method must be confirmed for the actual machines.
| Question | Multihead weigher | Checkweigher |
|---|---|---|
| Where is it in the process? | Before or at the filling stage | After the pack is formed, filled and normally closed |
| What does it weigh? | Product portions used to build a target dose | The completed pack, including product and packaging tare |
| Main control purpose | Create and discharge a dose for the packing machine | Verify finished-pack weight and trigger the agreed accept/reject action |
| Typical data | Individual hopper weights, selected combination, target, counts and supported alarms | Finished-pack weight, accept/reject status, trends and supported process data |
| Can it reject a finished pack? | Not normally; it is upstream of the finished pack | Yes, when integrated with an appropriate reject system |
| Can it influence the filler? | It directly controls its dose target and weighing sequence | Some systems can provide feedback, but this depends on supported controls and the validated line design |
Complete line sequence
Use both machines to separate dose creation from finished-pack verification.
Transfer product into the pack
The dose travels through the chute or timing hopper into the bag, pouch, jar, tray or other pack. Product loss, retention and timing can affect the finished result.
Complete the pack
The packer closes or seals the pack. Tare variation and any added components contribute to the checkweigher reading.
Verify and classify
The checkweigher measures the finished pack and applies the agreed accept, reject or alarm logic.
Review trends and feedback carefully
Where supported, a controlled feedback function may adjust the upstream target from finished-pack trends. Limits, delay, sample size, tare changes and fault handling must be defined so the loop does not chase noise or hide a mechanical problem.
Packaged-goods control
The packer remains responsible for the finished quantity and the evidence used to assess it.
GOV.UK states that weighing or measuring equipment used for packaged goods must be suitable and that packers using the average system must keep sample-batch records. A multihead weigher and checkweigher can support that process, but the legal and quality method must be defined for the actual product, pack and business.
Why does tare matter?
The checkweigher measures the complete pack. Film, pouch, tray, label or other packaging variation can change the reading even when the product dose is consistent. The sampling and control method should account for the chosen tare approach.
Which records should be kept?
Keep the equipment identity, target, sample sequence, results, rejects, alarms, adjustments and corrective action required by the site's control plan. For average-system requirements, follow current official guidance and local Trading Standards advice.
Buyer questions
Questions about multihead and checkweigher integration.
Do I need both a multihead weigher and a checkweigher?
That depends on the production and quality-control method. The multihead weigher creates the dose; the checkweigher provides independent finished-pack evidence and can support reject control. Some lines use sampling rather than 100% checkweighing.
Can a checkweigher improve multihead weigher accuracy?
A supported feedback function can adjust the upstream target from finished-pack trends, but it does not repair poor feeding, calibration, product loss, tare instability or an unsuitable configuration. The loop requires limits and validation.
Why can the checkweigher result differ from the multihead dose?
The finished pack includes packaging tare and can be affected by product retained or lost in the transfer path, product added elsewhere, spillage, pack contamination or timing errors.
Where should the reject system sit?
The line design should ensure a failed pack is identified, tracked and removed safely without creating ambiguity. Position depends on conveyor layout, pack stability, inspection equipment and the required reject confirmation.
What data should be shared between the machines?
Share only the information needed by the validated control philosophy, such as recipe identity, finished-pack trend, reject state or supported feedback value. Units, timing and fault behaviour must be documented.
How should feedback control be tested?
Use known changes and representative production to confirm response direction, rate limits, delay, reset behaviour, recipe change and what happens when checkweigher data are unavailable or unreliable.
Line review
Define dose creation, finished-pack verification and reject handling as one sequence.
Send the pack route, target, tare method, checkweigher requirement and controls interface.
Discuss the complete weight-control lineRelated guidance