Thick Film Current Sense Resistor Selection: 1,388 of 2,129 Size-Value-Tolerance Cells Offer More Than One Rated Power

A thick film current sense resistor value is not one part. We parsed all 5,047 commercial rows of Walsin’s thick film low ohm range and grouped them by case size, resistance and tolerance: 1,388 of 2,129 groups offer more than one rated power, and 0.100 ohm at 0805 offers four, from 1/8 W to 1/2 W.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the Walsin Technology (Walsin) current sense export, Thick_Film_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx, and 136 other chip resistor files. This post reads the three commercial series in it: 2,622 rows in Low Ohm, 2,169 in Power Low Ohm and 256 in the Reverse series. We set aside the 5,381 automotive rows in the same export, whose commercial twins are compared in the automotive upgrade-path post. Every part number below is real.

How many rated powers can one current sense value carry at one case size?

Up to four, and for most groups more than one. We grouped the 5,047 rows by case size, resistance string and tolerance, which gives 2,129 groups; 1,388 of them (65.2 percent) hold two or more rated powers, 1,342 hold two or more type codes, and 1,324 hold two or more TCR ceilings. The widest spread is 4 to 1, in 86 groups, every one at 0805.

Case size	Groups	Groups with 2+ rated powers	Most type codes in one group	Widest power ratio in one group	Match / mismatch against a filter on size, value and tolerance alone
0201	26	0	1	1.0	Match on 26 of 26 groups; one rating each
0402	288	248	4	2.0	Mismatch on 248 of 288 groups
0603	296	246	5	2.5	Mismatch on 246 of 296 groups
0805	316	293	5	4.0	Mismatch on 293 of 316 groups
1206	320	294	5	3.0	Mismatch on 294 of 320 groups
1210	315	102	2	2.25	Mismatch on 102 of 315 groups
1218	165	0	1	1.0	Match on 165 of 165 groups; one rating each
2010	201	103	2	2.0	Mismatch on 103 of 201 groups
2512	200	102	3	3.0	Mismatch on 102 of 200 groups

The 0815 size has 2 groups and one rating each. The counts come from Size, Resistance, Tolerance and Rated Power in Thick_Film_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx, read as raw strings. We have not seen this counted anywhere. A buyer who filters a current sense range by size, value and tolerance and expects one rating gets it in 741 of 2,129 groups and a pick-list in the other 1,388.

How are the six type codes spread across the three series names?

Unevenly, and the series name does not identify the code. We read the codes from the Part Number and Series columns of Thick_Film_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx. The fifth and sixth characters of the part number give six type codes in the 5,047 rows: XR 1,890, WR 1,222, PR 869, ER 762, CR 256 and TR 48. Two codes, WR and ER, sit in two different series names each.

Type code	Rows	Case sizes	Series names carrying it	Rated powers published	TCR ceilings published	Match / mismatch against “series name tells me the code”
XR	1,890	8 sizes, 0402 to 2512	Low Ohm (1,890)	1/16 W to 1 W	≦±300 to ≦±2100	Match, one series
WR	1,222	7 sizes, 0603 to 2512	Low Ohm (642), Power Low Ohm (580)	1/8 W to 2 W	≦±100 to ≦±1000	Mismatch, two series
PR	869	4 sizes, 0402 to 1206	Power Low Ohm (869)	1/8 W, 1/3 W, 1/2 W	≦±150 to ≦±300	Match, one series
ER	762	4 sizes, 0402 to 1206	Low Ohm (90), Power Low Ohm (672)	1/16 W to 1/2 W	≦±200 to ≦±1500	Mismatch, two series
CR	256	5 sizes, 0201 to 1206	Reverse (256)	1/10 W to 1/2 W	≦±100, ≦±150 and two ranges	Match, one series
TR	48	2512 only	Power Low Ohm (48)	3 W	≦±100 and ≦±200	Match, one series

Together the six codes carry 14 distinct TCR strings, two of which are ranges (0 ~ 250 and 0 ~ 350) and will not sort against a ceiling. A Power Low Ohm filter therefore returns four codes at once, and a Low Ohm filter three.

What does one 0805 value look like part by part?

Six part numbers, five type codes, four wattages, four TCR ceilings. At 0805, 0.100 ohm, plus or minus 1 percent, the commercial range lists WW08XR100FTL at 1/8 W and ≦±500, WW08ER100FTL at 1/4 W and ≦±600, WW08WR100FTL at 1/4 W and ≦±100, WW08CR100FTL at 1/3 W, WW08PR100FTL at 1/3 W and WW08WR100FTL FN at 1/2 W. The same six exist at plus or minus 5 percent.

Part	Series name	Type code	Rated power	TCR	Your incumbent part	Match / mismatch against WW08WR100FTL
WW08XR100FTL	Low Ohm	XR	1/8 W	≦±500	___	Match on size, value, tolerance; mismatch on power (half) and TCR (5 times looser)
WW08CR100FTL	Reverse	CR	1/3 W	≦±100	___	Match on size, value, tolerance, TCR; mismatch on power (1.33 times)
WW08ER100FTL	Power Low Ohm	ER	1/4 W	≦±600	___	Match on size, value, tolerance, power; mismatch on TCR (6 times looser)
WW08WR100FTL	Low Ohm	WR	1/4 W	≦±100	___	reference
WW08WR100FTL FN	Power Low Ohm	WR	1/2 W	≦±100	___	Match on size, value, tolerance, TCR; mismatch on power (double), series name and an embedded space
WW08PR100FTL	Power Low Ohm	PR	1/3 W	≦±150	___	Match on size, value, tolerance; mismatch on power (1.33 times) and TCR (1.5 times looser)

The same pattern holds at the neighbouring sizes. At 1206 the same 0.100 ohm, ±1 percent value lists WW12XR100FTL at 1/4 W, WW12WR100FTL at 1/3 W, WW12CR100FTL, WW12ER100FTL and WW12PR100FTL at 1/2 W, and WW12WR100FTL GN at 3/4 W. At 2512 it lists WW25XR100FTL and WW25WR100FTL at 1 W, WW25WR100FTL JN at 2 W and WW25TR100FZL at 3 W. A 3 to 1 spread, again from one value.

Where does the wattage upgrade hide in the part number?

In a two-letter tail after the tolerance and termination letters, often behind a space. Of the 5,047 commercial rows, 576 contain an embedded space; 50 end in FN, all 0805 and all 1/2 W; 50 end in DL, all 0603 and all 1/4 W; 132 end in GN, all 3/4 W, at 1206 and 1210. In the 0805 example above the tail raises the rated power over the tail-less stem and leaves resistance, tolerance and TCR as they were.

We did not first establish this: the tail code is decoded in full, with the TCR letter, in the part number tail code post, already published. What is new here is the count: every 0805 row rated 1/2 W (102 of 102) and every 1206 row rated 3/4 W (102 of 102) in the commercial range carries a tail. Copy a stem without its tail into a BOM and you select the lower rung silently; paste it with the space dropped and many systems fail the lookup. The embedded-space problem generally is covered in why Walsin part numbers do not paste into your BOM.

Which cells hold all five main type codes?

Six, and all six are the same value. Only 0.100 ohm at ±1 percent and ±5 percent, at 0603, 0805 and 1206, carries XR, WR, PR, ER and CR together; no other of the 2,129 groups does. At 0603 the six part numbers span 1/10 W to 1/4 W, at 0805 1/8 W to 1/2 W, at 1206 1/4 W to 3/4 W.

The reason is in the resistance ranges we read: CR tops out at 0.100 ohm, PR and ER start at 0.100 ohm at these sizes, and XR and WR span it. For a design at 0.100 ohm you hold the widest choice in the range, and the widest chance of copying the wrong rung. Above 0.100 ohm no group holds more than four codes.

How should a design pick a current sense part when the value alone is not enough?

Pick wattage and TCR first, then the code that carries both. Take your computed dissipation, add margin, and filter the 5,047 rows on rated power at or above it and on TCR at or below your budget; only then read the case size and the part number, including any tail. For a shunt that matters more than the nominal ohms, the TCR ceiling is the field to hold fixed: it ranges from ≦±100 to ≦±2100 across the codes.

Three working rules from the counts above:

1. Read the sixth and fifth characters together. WR is not XR; at 0805 they differ by a factor of two in power and five in TCR.
2. Keep the tail. FN, DL and GN are part of the part number and select the higher rung.
3. Confirm against the document. We hold 28 Walsin datasheets, 451 pages, and two are chip resistor sheets, WR general purpose and MR automotive. We hold none for the WW current sense series, so every rating above is the export’s figure and should be confirmed with Walsin before you qualify.

The free cross-reference tool lists these differences field by field, rated power and TCR included. What sits in Hong Kong is on ready stock: 1,125 part numbers as at 23 September 2026, a dated snapshot and not a live feed. The broader range is on the chip resistor page, and the thick film against metal question is in low ohm current sense, thick film or metal.

The short version

A current sense value is a pick-list. We parsed 5,047 commercial Walsin thick film low ohm rows into 2,129 size-value-tolerance groups: 1,388 hold more than one rated power, 1,342 more than one type code, and 86 spread 4 to 1 in power, all at 0805. Six type codes, XR, WR, PR, ER, CR and TR, share three series names, and WR and ER sit in two names each. 0.100 ohm is the one value held by all five main codes, at three sizes and two tolerances. The top wattage rung at 0805, 0603 and 1206 hides in a tail with a space. We will not tell you which part to fit. We will show you the field the export holds. Qualification stays with you.

Send us the shunt positions on your BOM with the dissipation and TCR budget each must meet, and we will list every Walsin row that clears both. And a question back: when your BOM says 0.100 ohm 0805, which of the six did you mean?

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Frequently asked questions

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