Chip Resistor Part Number Decoding: 26 of 234,815 Walsin Rows Contradict Their Own Code

Chip resistor part number decoding is a cross-check, not a convenience. We decoded the resistance, tolerance and size fields out of every Walsin chip resistor part number and compared each one against the column beside it. 26 of 234,815 rows disagree with their own code — including two current-sense shunts published at three times their coded value.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds all 137 chip resistor export files published by Walsin Technology (Walsin) and both chip resistor datasheets, Walsin_WR_General_Purpose_Chip_Resistor.pdf and Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf. The ordering key on page 6 of the WR sheet and page 4 of the MR sheet gives the part-number grammar, so the part number and the parametric columns are two independent statements of the same specification. We checked them against each other. Every part number below is real.

What does a Walsin chip resistor part number actually encode?

Six fields, in a fixed order. Both datasheets we hold print the same ordering key: size code, type code, resistance code, tolerance code, packaging code, termination code. WR06X1002FTL reads as WR06 for 0603, X for the type, 1002 for 10,000 Ω, F for ±1%, T for 7-inch reeled taping and L for tin-base termination. We decoded the resistance code on 217,180 of the 234,815 rows; the other 17,635 use a grammar the two sheets we hold do not document.

Position	Example from WR06X1002FTL	What the datasheet ordering key says	Column that restates it
Size code	WR06	0603	Size
Type code	X	E24, 2 significant figures	none
Resistance code	1002	10,000 Ω	Resistance
Tolerance code	F	±1%	Tolerance
Packaging code	T	7-inch reeled taping	Packaging
Termination code	L	Sn base	Termination

Three of the six are restated in a column, and that redundancy is the only free integrity check anybody gets on this data. We ran it. For the wider problem of what these codes do to a bill of materials, see why Walsin part numbers do not paste into your BOM.

How many rows disagree with their own resistance code?

Twenty, of 217,147 rows where both the code and the column could be read as a number. We decoded R-prefixed millionths, nnRm decimals and the three- and four-digit significant-figure-plus-multiplier forms, then compared each to the Resistance cell to nine significant figures. 217,127 agree exactly. The 20 that do not split into two clusters, and both clusters are tight enough to show you what went wrong.

Cluster	Rows	Code says	Column says	Where
30R1 in the High Precision TC50 shelf	18	30.1 Ω	30.25 Ω, 30.50 Ω or 31.0 Ω	High_Precision_Thick_Film_chip_resistor_*.xlsx
R001 and R002 metal plate current sense	2	0.001 Ω and 0.002 Ω	0.003 Ω on both	Metal_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx

Twenty in 217,147 is a rate of about one in eleven thousand. We have not seen this counted anywhere, and the rate is not the point — the location is.

Why does one 30.1 ohm position read 30.25, 30.50 and 31.0 ohm?

Because the cell has been filled with 30 plus the tolerance figure, on all 18 rows. We read them in their own files. At ±0.25% the Resistance column reads 30.25 Ω; at ±0.5% it reads 30.50 Ω; at ±1% it reads 31.0 Ω. The pattern holds across three case sizes, three tolerances and both the commercial and automotive halves of the TC50 series, which is 18 rows and no exceptions.

Part number	Size	Resistance code	Column reads	Tolerance	Match / mismatch
WF12K30R0FTL	1206(3216)	30R0 = 30.0 Ω	30.0 Ω	±1%	Match — the neighbour below
WF12K30R1FTL	1206(3216)	30R1 = 30.1 Ω	31.0 Ω	±1%	Mismatch — 30 plus the tolerance figure
WF12K30R9FTL	1206(3216)	30R9 = 30.9 Ω	30.9 Ω	±1%	Match — the neighbour above
WF06K30R1CTL	0603(1608)	30R1 = 30.1 Ω	30.25 Ω	±0.25%	Mismatch — same position, tighter tolerance
WF12K30R1FTLJ	1206(3216)	30R1 = 30.1 Ω	31.0 Ω	±1%	Mismatch — the automotive twin inherits it

The two rows that bracket it in the same E96 decade are correct, and 209 other rows elsewhere in the export do publish a clean 30.1 Ω, so the value itself is not missing from the catalogue. Only this position in this shelf is wrong. A ±1% part specified at 30.1 Ω and selected from the column instead of the code lands on a figure 3% high, which is three times the tolerance band it was chosen for.

Which two current-sense shunts publish the wrong resistance?

WW12MR001FTL and WW12MR002FTL, both published at 0.003 Ω. Their resistance codes are R001 and R002, which the ordering key makes 0.001 Ω and 0.002 Ω, and their own automotive twins publish those values correctly. This is the sharpest of the 26 because a current-sense shunt is the one resistor whose exact value sets a measured current, and 0.003 Ω against 0.001 Ω is a factor of three.

Part number	Series	Size	Code says	Column says	Match / mismatch
WW12MR001FTL	Metal Plate Low Ohm Current Sense	1206(3216)	0.001 Ω	0.003 Ω	Mismatch — 3× the coded value
WW12MR001FTLJ	Metal Plate Low Ohm Current Sense (Automotive)	1206(3216)	0.001 Ω	0.001 Ω	Match — the automotive twin is right
WW12MR002FTL	Metal Plate Low Ohm Current Sense	1206(3216)	0.002 Ω	0.003 Ω	Mismatch — 1.5× the coded value
WW12MR001FTLJ and WW12MR002FTLJ together	Metal Plate Low Ohm Current Sense (Automotive)	1206(3216)	0.001 and 0.002 Ω	0.001 and 0.002 Ω	Match — both correct

The commercial rows are wrong and the automotive rows beside them are right, which is as clean a demonstration as we could ask for that the code, not the column, is the authority. We hold no datasheet for the WW metal plate series. For how thinly this shelf is specified in general, see low-ohm current sense, thick film against metal.

Which rows disagree with their own tolerance letter?

Three, and all three sit in the low-ohm current sense groups. We pulled the tolerance letter out of every part number and crossed it against the Tolerance column across all 234,815 rows: F resolves to ±1% on 125,969 rows and to ±5% on 2; J resolves to ±5% on 33,594 rows and to ±1% on 1. Those three rows are the whole discrepancy.

Part number	Letter	Letter means	Column says	Size	Match / mismatch
WW20MR015FTL	F	±1%	±5%	2010(5025)	Mismatch — and identical in every other column to WW20MR015JTL
WW20MR015JTL	J	±5%	±5%	2010(5025)	Match
WW15WR010FTL	F	±1%	±5%	0815(2037)	Mismatch
WW15WR005JTL	J	±5%	±1%	0815(2037)	Mismatch

The 0815 case size is the rarest in the whole chip resistor catalogue — exactly 4 part numbers of 234,815 — and we read all four. They form two pairs, R005 and R010, and within each pair the F row and the J row are identical in every published column including TCR and rated power. The tolerance and the temperature coefficient track the resistance value rather than the tolerance letter, so on this shelf the F and J suffixes cannot be told apart from the data at all.

Can the two-digit size code resolve a case size on its own?

Not on 11 codes out of 11 without a second look, and not at all on 3 rows. We crossed the two digits after the prefix against the Size column on all 234,815 rows. Six codes resolve to exactly one case size. Five resolve to between two and four, and four of those five are a documented reversal — the wide-terminal parts put the short edge first, so 0612 files under 12, 1020 under 20, 1225 under 25 and 0306 under 06.

Size code	Case sizes it names	Rows	Match / mismatch with the code read naively
06	0603, 0602×8 array, 0306, 0805	42,374 / 555 / 10 / 3	Mismatch — four outcomes from one code
25	2512, 1225	22,154 / 1,755	Mismatch — reversed-digit wide terminal
12	1206, 0612	37,468 / 1,725	Mismatch — reversed-digit wide terminal
20	2010, 1020	21,228 / 878	Mismatch — reversed-digit wide terminal
04	0402, 1206	28,085 / 98	Mismatch — WT04 networks are 0402 elements in a 1206 body
01, 02, 08, 10, 15, 18	one each	755 to 38,041	Match

The three rows in bold have no convention behind them. WF06S1R0 JTL, WF06S1R1 JTL and WF06S1R2 JTL carry size code 06 and a Size column reading 0805(2012). Their 142 siblings in the same file, WF06S1R3 JTL onward, all read 0603(1608). All three are rated 1/10 W, which is the 0603 rating on this shelf; the genuine 0805 part at the same resistance, WF08S1R0 JTL, is rated 1/8 W. Three independent signals — the size code, the siblings and the wattage — say 0603 and the Size column says 0805.

Lay the wrong land pattern for a 1.0 Ω anti-surge part and you find out at first article, not at design review. For the array and network cases where the Size column names a geometry rather than a footprint, see the 1225 problem.

What should you do before a part number enters your library?

Decode it and compare, every time, because it costs nothing and it caught 26 rows here. The part number and the columns are two independent statements. Where they agree you have a free confirmation; where they disagree you have found something worth an email before you have found it on a board.

1. Cross the whole list in one pass. Paste up to 500 part numbers or drop your Excel or CSV into the free cross-reference tool, filter by commercial or automotive grade, and read every stated difference rather than a claimed match. It decodes 18 manufacturers’ part numbers against 800,000+ crossable Walsin part numbers.
2. Check what is physically in Hong Kong on ready stock — 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed.
3. Ask us for the sheet that governs your part. We hold 28 Walsin datasheets, 451 pages, of which exactly two are chip resistor documents. The WR sheet is ASC_WR_V24, dated September 2016, and we hold no public URL for either file.

Unit 207, 2/F, Sun Ling Plaza, 30 On Kui Street, Fanling, N.T., Hong Kong. (852) 2628 4777. Hong Kong, Shenzhen, Singapore and Jiangmen, with Chengdu in preparation. The range sits on the Walsin chip resistor page.

The short version

We decoded the resistance, tolerance and size fields out of all 234,815 Walsin chip resistor part numbers and compared each against the column beside it. 26 rows disagree. Twenty are resistance: 18 at the 30R1 position in the High Precision TC50 shelf, where the cell reads 30 plus the tolerance figure, and 2 metal plate shunts published at 0.003 Ω against coded values of 0.001 Ω and 0.002 Ω. Three are tolerance, all in the low-ohm current sense groups. Three are size: WF06S1R0 JTL, WF06S1R1 JTL and WF06S1R2 JTL read 0805 while their code, their 142 siblings and their wattage all say 0603. We will show you where a manufacturer’s own two statements of the same part differ from each other. Qualification stays with you.

Send us the resistor lines off your bill of materials and we will decode every one against its own columns and tell you which fields confirm each other and which do not. And a question back: when your library pulled these parts in, which of the two statements did it believe?

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Frequently asked questions

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