There are two main ways to count products on a conveyor. Photo-eye or beam sensors count each time a product breaks a light beam, which works when products travel one at a time with gaps between them. Vision counting uses a camera above the belt to detect and track every item in its field of view, so it can count products that touch, overlap or arrive in mixed types, and send live counts to the line’s PLC or HMI.
This article is part of our complete guide to automated counting, which covers every way of counting parts in production. Here we focus on inline counting: counting products where they already are, on a moving belt.
Conveyor counting methods compared
| Method | How it counts | Works well when | Struggles when |
|---|---|---|---|
| Photo-eye (beam) sensor | Counts each break in a light beam | Products are singulated with clear gaps | Products touch, overlap, tumble or arrive side by side |
| Light curtain | Counts interruptions across a grid of beams | Products fall or pass through a defined zone | Products are tiny or arrive in clusters |
| Vision counting | A camera detects and tracks each item in the image | Products touch, overlap, vary in size or arrive mixed | The camera cannot see the item, for example parts buried in a pile |
| Checkweigher | Weighs packages on the belt | Checking that a filled package is within weight limits | You need the number of pieces, not the weight |
Beam sensors are inexpensive and reliable for evenly spaced products. Once products bunch up, two items passing together read as one, and the count drifts. Vision counting replaces the single beam with an image of the whole belt width, so the software sees each item even when they are touching.
How vision counting on a conveyor works
- Image the belt: a camera above the conveyor captures a continuous series of frames across the full belt width, under controlled lighting.
- Detect each item: image analysis finds every product in the frame, including items that touch or partly overlap.
- Track it across frames: each item is followed as it moves, so it is counted once even though it appears in many frames.
- Count, by type if needed: single product types are counted directly; mixed products can be counted by type when they look different.
- Send the result: the running count goes to a PLC or HMI to trigger packing, diverting or batch changes.
Worked example: why tracking matters
On a belt moving at 0.5 m/s with a camera covering 0.4 m of belt length, each item is in view for 0.4 ÷ 0.5 = 0.8 seconds. At 20 frames per second, the camera sees every item in about 16 frames. Without tracking, each item could be counted 16 times. Tracking links those detections into one object, so each item is counted exactly once.
The ConveyorCount conveyor counting system is built around this approach. The image analysis behind it ranges from rule-based to machine learning or AI, depending on what the products look like and how much they vary.
Inline counting or batch counting?
Counting on the conveyor is not always the best choice. If parts are loose and small, it is often faster and more accurate to count them in a batch counter before or after the line.
| Inline (on the conveyor) | Batch (drop zone counter) | |
|---|---|---|
| Where parts are | Already moving on a line | Loose, in bulk, poured into a hopper |
| Typical products | Packaged goods, assemblies, larger parts, mixed items | Small parts, fasteners, pellets, seeds |
| Speed | Set by the line | Up to 2,000 parts per second |
| Output | Running count to PLC or HMI | Exact batches into bags, boxes or kits |
| Example system | ConveyorCount | PerfectCount |
For batch counting of small parts, see how to automate bulk and batch counting.
What affects counting accuracy on a conveyor
- Spacing: products that are piled on top of each other cannot all be seen. Touching and overlapping are fine for vision; stacking usually needs the flow spread out first.
- Contrast: the product should stand out from the belt. A belt color chosen for contrast, or the right lighting, makes detection more reliable.
- Lighting: enclosed, even lighting removes the effect of changing plant light and glare from shiny products.
- Belt speed and frame rate: the camera must capture each item several times as it passes so tracking stays reliable.
- Product variation: the more products vary in shape, color or orientation, the more capable the image analysis needs to be.
Connecting conveyor counts to the line
- Trigger a packer, case packer or bagger when a batch count is reached.
- Divert or reject items that should not be counted, such as wrong products in a mixed stream.
- Display live counts and rates on an HMI so operators can see the line at a glance.
- Log counts by batch, shift or order for production records and traceability.
Common mistakes
- Using a beam sensor where products bunch up, then trying to fix the count with software timing tricks.
- Mounting a camera without controlling lighting, so counts change with the time of day.
- Ignoring how products arrive at the counting point. A small change to guides or spacing can make counting far more reliable.
- Counting piled products. If items can hide under each other, spread them out or count them before they pile up.
Need to count products on a moving line?
Sciotex designs and builds conveyor and vision counting systems that send live counts to your PLC or HMI, designed, programmed, built and supported in the US since 1997.
Frequently asked questions
Use a photo-eye sensor if products are evenly spaced, or a vision counting system with a camera above the belt if products touch, overlap or arrive mixed. Vision systems track each item so it is counted once.
Beam sensors count each break in the beam, so two products passing together read as one and gaps inside a product can read as two. Vision counting avoids this by detecting each item in the image.
Yes. A vision counting system can count different products separately when they look different, and send the counts for each type to the line controls.
Yes. Image analysis separates items that touch or partly overlap. Products piled on top of each other may need to be spread out first so each one is visible.
Count on the conveyor when products are already moving on a line. For loose small parts packed in exact quantities, a drop zone batch counter is usually faster and more accurate.