A current sense resistor for data-centre power in Portugal often has to sit at 5 milliohm or below, and in Walsin Technology (Walsin) chip resistors that is almost entirely metal: we counted 317 metal parts at or under 5 milliohm against 2 in thick film, and none of the 317 is on our shelf.
Venatech Limited, an authorised Walsin distributor in Hong Kong, wrote this from the Walsin chip resistor exports (137 .xlsx files, 234,815 rows, 234,401 distinct part numbers re-counted by us on 11 November 2026) and our stock list as at 23 September 2026. It is written for a designer of rack power shelves, power distribution or battery-backup boards for the Portuguese data-centre build-out. Every part number is real. News figures name their source and the date we fetched them, 11 November 2026. This is engineering perspective, not legal advice.
What did Portugal’s government propose for data centres?
Rules tying new data centres to renewable power and to cooling that does not draw on fresh water. BeBeez International reported on 4 November 2026, citing DCD, that Portugal’s government drafted rules requiring data centres to run on renewable power and to use waterless cooling or a water solution that does not compete with public supply.
The same report says more than 2.6 GW of data-centre capacity is under development in Portugal, with 36 data centres operating and 10 more under construction or planned, and the Start Campus project at Sines planned at 1.2 GW. It adds that Spain revised its own data-centre rules in October. Those are the report’s figures, not ours, and the article gives no threshold or effective date for the Portuguese rules.
What does a hotter, waterless data hall mean for a current sense resistor?
It puts more weight on two fields: rated power and TCR. Our worked example: at 40 A, a 1 milliohm shunt dissipates 1.6 W, and with a rule of rated power at least twice the dissipation, which is our assumption and not a standard, it needs 3.2 W; no Walsin 2512 part at 1 milliohm reaches that, so the brief moves to 0.5 milliohm.
Cooling without evaporative water tends to mean warmer air at the board, though the outcome depends on the design of each hall, and the export carries no derating curve. A warmer board derates the resistor further and makes TCR, the drift of resistance with temperature, show up as measurement error. Our post on low-ohm current sense: thick film versus metal covers the trade-off; chip resistor power rating by case size covers the ceiling each footprint sets.
How low does a Walsin current sense resistor go, and in which technology?
Thick film stops at 5 milliohm; metal goes to 0.5 milliohm. We counted 1,188 distinct metal low-ohm parts and 10,428 thick-film low-ohm parts. Thick film reaches 5 milliohm only in the 0815 size and 10 milliohm in every other size; metal reaches 0.5 milliohm in 2512, 1225 and 0612.
| Resistance band | Metal low-ohm parts | Thick-film low-ohm parts | On shelf 23 Sep 2026 |
|---|---|---|---|
| 1 milliohm or below | 58 | 0 | 0 |
| Above 1, up to 2 milliohm | 56 | 0 | 0 |
| Above 2, up to 5 milliohm | 203 | 2 | 0 |
| Above 5, up to 10 milliohm | 321 | 32 | 0 |
| Above 10, up to 100 milliohm | 506 | 1,727 | 0 |
Our whole current-sense shelf is 3 lines, all thick film in 0805 at 0.27, 0.39 and 0.47 ohm, such as WW08WR470FTL. TCR separates the two technologies as well: every metal part is rated at or inside plus or minus 150 ppm per degree Celsius, and 612 of them at plus or minus 50, while thick-film ratings run up to plus or minus 2,100. We have not seen this split counted elsewhere.
Which Walsin parts answer a 1 milliohm, 2512, 2 W shunt brief, and what differs?
Ten of the 28 Walsin 2512 parts at 1 milliohm do: the plus or minus 1 percent ones rated 2 W or 3 W. At 1 milliohm in 2512 we counted 28 part numbers, 14 at plus or minus 1 percent, rated 1 W, 2 W or 3 W, so the current at rated power runs from about 31.6 A to 54.8 A in the same footprint.
| Walsin part | Series | Rating / TCR | On shelf | Match / mismatch with the 1 milliohm, 1%, 2512, 2 W+ brief | Your incumbent |
|---|---|---|---|---|---|
WW25BR001FTL |
Metal plate | 3 W, 70 ppm | No | Match, with the most headroom | |
WW25AR001FTL |
Metal plate power | 3 W, 70 ppm | No | Match | |
WW25RR001FTL |
Metal plate power | 2 W, 75 ppm | No | Match at the floor of the brief | |
WW25RR001FTLJ |
Metal plate, automotive | 2 W, 100 ppm | No | Match on rating; mismatch on TCR against its own base code | |
WW25JR001FTL |
Metal plate | 1 W, 70 ppm | No | Mismatch: half the rating | |
WW12RR001FTL |
Metal plate, 1206 | 1 W, 70 ppm | No | Mismatch on footprint and rating | |
WW08WR470FTL |
Thick film, 0805 | 1/4 W | Yes | Mismatch: 470 times the resistance |
A match is a match on the export fields only. Confirm against both datasheets and qualify in your own circuit, including Kelvin layout and solder-joint temperature. We hold no Walsin datasheet for the metal low-ohm series among our 28 datasheet files, so request the datasheet for the exact series before design-in.
Why does the J suffix matter on a Walsin metal shunt?
Because the automotive twin does not always carry the same TCR. We paired every Walsin metal current-sense code with the same code plus a trailing J and found 502 such pairs; in 42 of them the TCR differs, and in 1 the rated power differs.
WW25RR001FTL is rated 75 ppm and WW25RR001FTLJ 100 ppm; WW25QR002FTL and WW25QR002FTLJ differ the other way, 100 against 70. A buyer who adds a J to move a board onto an automotive series, or drops one to save cost, can change the measurement error without changing the footprint. Read the TCR field on both codes before you swap.
How can Venatech help a Portuguese data-centre power team?
How Venatech helps: the 1,188 metal shunts above are all searchable in the free tool. The cross-reference tool, VenaMatch, decodes 18 manufacturers’ part numbers across 800,000+ crossable parts, accepts up to 500 part numbers or an Excel or CSV file, and states every difference from your original, TCR included.
Upload a power-shelf list at BOM upload to request a quote. The ready-stock list is a Hong Kong snapshot dated 23 September 2026 and holds no metal shunt, so these are to-order enquiries; the chip resistor range lists the families. Walsin is the only line we are authorised for; Stackpole and Viking are lines we supply. We serve from Hong Kong in small lots, with no price, lead time or stock guarantee, no office or stock in Portugal, and no compliance advice: confirm with your compliance team.
The short version
Portugal’s draft data-centre rules point at renewable power and waterless cooling, and a warmer hall makes shunt rating and TCR matter more. In Walsin, 5 milliohm and below means metal: 317 parts against 2 in thick film. At 1 milliohm in 2512 the rating spans 1 W to 3 W, and the J suffix changes TCR on 42 of 502 pairs.
Send us your shunt lines with the current and ambient you design for, and we will return the Walsin metal candidates with every difference stated. At your current, is 1 milliohm still the right value, or is 0.5?
Sources
Fetched 11 November 2026.
- BeBeez International, “Portuguese govt drafts new rules requiring data centers to be powered via renewable energy”, 4 November 2026: https://bebeez.eu/2026/11/04/portuguese-govt-drafts-new-rules-requiring-data-centers-to-be-powered-via-renewable-energy/
Related reading
- Low-ohm current sense: thick film versus metal
- Chip resistor power rating by case size
- Tolerance, TCR and dielectric codes decoded
- Free tools: VenaMatch cross reference and the ready stock list
Last reviewed 11 Nov 2026.
Frequently asked questions
<!– wp:rank-math/faq-block {"questions":[{"id":"faq-question-01","title":"What did Portugal propose for data centres in November 2026?","content":"BeBeez International reported on 4 November 2026 that the government drafted rules requiring data centres to run on renewable power and use waterless cooling or a non-competing water solution. The same report cites more than 2.6 GW of capacity in development.","visible":true},{"id":"faq-question-02","title":"How low does a Walsin thick-film current sense resistor go?","content":"To 5 milliohm, and only in the 0815 size; every other thick-film size stops at 10 milliohm. Walsin metal low-ohm parts reach 0.5 milliohm in 2512, 1225 and 0612. We counted these from the chip resistor exports.","visible":true},{"id":"faq-question-03","title":"What rating does a 1 milliohm 2512 current sense resistor carry in Walsin's range?","content":"We counted 28 Walsin 2512 parts at 1 milliohm, 14 at plus or minus 1 percent, rated 1 W, 2 W or 3 W. That is roughly 31.6 A to 54.8 A at rated power before any derating. Check the derating curve in the datasheet.","visible":true},{"id":"faq-question-04","title":"Does adding the J suffix change a Walsin metal shunt?","content":"Sometimes. Of 502 base and J-suffix pairs we checked, 42 differ in TCR and 1 in rated power.WW25RR001FTL is 75 ppm and WW25RR001FTLJ 100 ppm. Read both codes before swapping.”,”visible”:true},{“id”:”faq-question-05″,”title”:”Are any Walsin metal current sense resistors on your shelf?”,”content”:”No. The current-sense shelf as at 23 September 2026 is 3 thick-film 0805 lines between 0.27 and 0.47 ohm. Metal shunts are to-order enquiries, and we give no price, lead time or stock guarantee.”,”visible”:true},{“id”:”faq-question-06″,”title”:”Do you give compliance advice on Portugal’s data-centre rules?”,”content”:”No. This is engineering perspective only. We hold no office or stock in Portugal and give no legal, customs or compliance advice. Confirm the final rules and their dates with your compliance team.”,”visible”:true}],”listStyle”:””,”titleWrapper”:”h3″,”titleCssClasses”:””,”contentCssClasses”:””,”sizeSlug”:””} –>
What did Portugal propose for data centres in November 2026?
BeBeez International reported on 4 November 2026 that the government drafted rules requiring data centres to run on renewable power and use waterless cooling or a non-competing water solution. The same report cites more than 2.6 GW of capacity in development.
How low does a Walsin thick-film current sense resistor go?
To 5 milliohm, and only in the 0815 size; every other thick-film size stops at 10 milliohm. Walsin metal low-ohm parts reach 0.5 milliohm in 2512, 1225 and 0612. We counted these from the chip resistor exports.
What rating does a 1 milliohm 2512 current sense resistor carry in Walsin’s range?
We counted 28 Walsin 2512 parts at 1 milliohm, 14 at plus or minus 1 percent, rated 1 W, 2 W or 3 W. That is roughly 31.6 A to 54.8 A at rated power before any derating. Check the derating curve in the datasheet.
Does adding the J suffix change a Walsin metal shunt?
Sometimes. Of 502 base and J-suffix pairs we checked, 42 differ in TCR and 1 in rated power. WW25RR001FTL is 75 ppm and WW25RR001FTLJ 100 ppm. Read both codes before swapping.
Are any Walsin metal current sense resistors on your shelf?
No. The current-sense shelf as at 23 September 2026 is 3 thick-film 0805 lines between 0.27 and 0.47 ohm. Metal shunts are to-order enquiries, and we give no price, lead time or stock guarantee.
Do you give compliance advice on Portugal’s data-centre rules?
No. This is engineering perspective only. We hold no office or stock in Portugal and give no legal, customs or compliance advice. Confirm the final rules and their dates with your compliance team.