Data Matrix: a code for tiny items

A medicine blister, a circuit board, a syringe cap, a tiny bolt: an ordinary barcode will not fit on such an item. An EAN-13 alone is over 30 mm long, and a QR code takes quite a lot of room even with its quiet zone. Data Matrix was created for this problem, and it is widely used to mark medicines and small parts.

What Data Matrix is

Data Matrix, like QR, is a two-dimensional code built from square cells. It is easy to recognise: the left and bottom edges form a solid black "L" line, while the top and right edges consist of alternating black and white cells. The scanner uses that "L" to find where the code is.

The main properties:

• Very small size: the smallest code is only 10×10 modules. With a 0.25 mm module it fits an area under 3 mm.
• Capacity: the large versions hold over 3,000 digits or over 2,000 letters and digits.
• Error correction: the modern ECC 200 variant corrects errors with the Reed-Solomon method, so the code can be read even if part of it is damaged.
• Narrow quiet zone: one module of blank space around it is enough, whereas QR needs four.

Data Matrix is not limited to paper. It can be etched into metal or plastic with a laser, struck in with dot peen or applied by inkjet, which makes it handy for lifetime marking of spare parts and components.

Where it is used

Electronic components and boards, car and aircraft parts, medical devices, laboratory test tubes, jewellery and tools. It is especially common on medicines: in many countries each pack is tracked through Data Matrix with its own serial number. In Uzbekistan digital marking has also been introduced, or is being introduced, for certain groups of goods; check the current requirements with the official sources of the authorised bodies.

GS1 DataMatrix: what is inside

In retail and pharmaceuticals Data Matrix is filled according to GS1 rules. Several fields are written one after another, each starting with a numeric application identifier (AI). For example:

• (01) the product number (GTIN), 14 digits;
• (17) the expiry date as YYMMDD;
• (10) the batch number;
• (21) a unique serial number for each unit.

In human-readable form it looks like (01)04780000123454(17)271231(10)LOT7(21)000123; the brackets are not written into the code itself. When a variable-length field (the batch, for example) is followed by another field, a special separator goes between them. It is invisible on screen, so the software must be set up to parse the code properly. Otherwise batch and serial run together.

Scanner and printer requirements

1. An imager scanner: a laser scanner does not read Data Matrix. A phone camera does not always recognise it either: a separate app is often needed.
2. Printer resolution: on a 203 dpi printer the module is a multiple of 0.125 mm, and a tiny code comes out blurred. For small labels choose a printer of 300 dpi or better.
3. Contrast and surface: a code on a glossy or curved surface may fail to scan. Choose a matt label and keep the surface flat.
4. Testing: if you mark a part directly, scan a few samples at the start of each batch.

When you need it in a warehouse

If the item is small and every unit must be tracked individually (warranty, returns, serial-number records), Data Matrix is a logical choice. For ordinary goods, where there is room, EAN-13 or Code 128 is cheaper and simpler. The drawback of Data Matrix is that it needs an imager scanner and a more accurate printer.

A worked example: the internal number A12-0417 (8 characters) fits a code of 12×12 modules, because pairs of digits are written compactly. With a 0.25 mm module the code, quiet zone included, comes to about 3.5 mm. In Code 128 the same entry would be about 30 mm long.

Conclusion

Data Matrix is a code for items with little room: it holds a lot of data in a tiny area and survives damage. The Shtrix team reads such codes during a count, and if internal codes are needed it prepares suitable labels for goods and parts.