> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/microarray/general/microarray-general-faq-list/000009190.md).

# Why do different BeadChip types with the same format (HD, HTS, or LCG) have different numbers of stripes scanned per sample?

Different BeadChip types of the same format (HD, HTS, or LCG) might have different numbers of stripes to be scanned. For example, one HD BeadChip type may have three stripes per sample, while another HD BeadChip type will scan five stripes.

**What determines the number of stripes per sample to be scanned?**

The number of stripes scanned for each sample is determined by the array's probe content (plexity) and the level of bead redundancy required to generate reliable data.

During scanning, each bead type needs to be represented multiple times, on average, a redundancy of approximately 15 to 30 beads per bead type for each sample. To determine the number of stripes to scan, Illumina selects only the minimum number of stripes required to achieve the required bead redundancy across all bead types.

For low-plexity BeadChips, which contain somewhere in the range of a few thousand to several tens of thousands of probe types per sample, only one stripe is required to reach that redundancy, since each stripe has a capacity for millions of beads.

For higher-plexity BeadChips, containing hundreds of thousands to several million probe types per sample, additional stripes are required to attain that redundancy of probes for each sample. As plexity increases, more stripes must be scanned to maintain the required redundancy across the array.

Illumina scans only the minimum number of stripes required to achieve the target bead redundancy. Scanning additional stripes does not provide any benefit once the required level of redundancy has been reached. For example, scanning four stripes for a very low-plexity array would generate more than four times the amount of data needed to achieve the target redundancy.

Each stripe requires several minutes to scan and process, including image acquisition and intensity extraction. By scanning only the necessary number of stripes, the system minimizes overall scan time while maintaining data quality. This approach does not result in any loss of data. Instead, it improves efficiency by reducing the time required to scan and process each sample while ensuring the necessary bead redundancy is achieved.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #9190), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000009190%20-%20Microarray%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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