Here's my conclusion before anything else: during the chip shortage, I rejected 12% of first deliveries in 2024—and almost none of them were Vishay parts. That's not because Vishay is immune to manufacturing defects. It's because the "equivalent" components from alternative suppliers were, more often than not, not actually equivalent. If you're buying passive components right now, you need to verify every batch yourself. This article shows you how I test Vishay Dale resistors and Vishay NTC thermistors with a basic multimeter—and why the chip shortage made that kind of verification more critical, not less.
It took me about 130 component deliveries to understand that "within spec" and "good enough" are not the same thing. And it took one really bad batch to understand the difference in dollars, not just in theory.
The Batch That Changed My Testing Protocol
The component shortage between 2021 and 2024 created a strange market. Parts were expensive, lead times stretched to uncomfortable lengths, and a gray market grew where components were stripped from old boards, relabeled, or replaced with parts that sort of matched the original specs but quietly didn't hold up.
In March 2023, we received 5,000 through-hole resistors from a broker we hadn't used before. Packaging looked right. Paperwork matched. Price was about 30% below the Vishay Dale equivalent—which, honestly, should have been a red flag. My team pulled 30 random samples from five different reels and tested resistance against our required ±1% tolerance.
Twelve of the thirty measured outside that range. Twelve out of thirty.
The vendor claimed the parts were "within industry standard." Maybe they were. But our standard is ±1%, and these parts weren't. We rejected the whole batch. The replacement batch passed, but we lost about $22,000 in added testing, revalidation paperwork, and a delayed production run.
What bothered me most? We were using the same words as the vendor but meaning different things. "Reliable parts" meant one thing to their sales department and something else entirely to our inspection team. That's when I realized my verification protocol—which I'd written in 2022—needed to be more formal, with documented results before a single reel gets accepted. We had the process in theory. The March 2023 batch proved we didn't have it in practice.
How I Test Vishay Dale Resistors
The Dale resistor line, now made under the Vishay name, earned its reputation decades ago. The RNR series is still specified in military applications (MIL-PRF-55182, for anyone who wants to look it up). These parts hold tight tolerances, and their resistance stays stable as temperature changes. But reputation doesn't mean you skip verification—it means you verify against a known-good reference.
Here's what I do with precision resistors, through-hole or SMD:
- Measure at room temperature. Set the multimeter to resistance mode, connect the probes (Kelvin clips are better for low values), and record the reading. A 1% resistor should measure within 1% of its stated value at 25°C. If it's at the edge, I flag it. Edge-of-spec parts might pass today and fail tomorrow.
- Warm it up and measure again. Apply power for about 30 seconds, then re-measure. The resistance should be basically stable. Cheap resistors and relabeled parts tend to drift much more as they heat. You'll see the value wander in ways the datasheet doesn't explain.
- Check the temperature coefficient. Vishay publishes TCR (temperature coefficient of resistance) for every series. Military-rated parts like the RNR series are typically around ±25 ppm/°C. If you're measuring significantly more drift than the datasheet allows, something is off.
For SMD resistors—like the CRCW series—the process is identical, but I use four-wire Kelvin clips to eliminate test lead resistance. A standard pair of leads can add 0.1 Ω or more to a measurement. On a 10 Ω resistor, that's a full 1% error. You can't verify a 1% part with a sloppy measurement setup.
Testing Vishay NTC Thermistors Is Honestly Simple
Vishay NTC thermistors are everywhere—battery temperature sensing, inrush current limiting, HVAC controls. An NTC (negative temperature coefficient) thermistor drops its resistance as temperature goes up. That's the opposite of a normal resistor, and it makes testing pretty straightforward.
- Measure resistance at room temperature. Write it down.
- Warm it up. Hold it between your fingers for about ten seconds. The resistance should drop noticeably. If it barely moves, the part is damaged or it's not the right type.
- Do the two-point check. For a more thorough test, measure resistance at two known temperatures—room temperature and boiling water (about 100°C at sea level). The ratio of those readings should match what the datasheet's B-value predicts. If it doesn't, the thermistor isn't what the label claims.
One safety note: don't dunk a thermistor that's still soldered to a board into boiling water. Test it loose, let it cool, dry it completely. We've had engineers skip the drying step and then chase phantom measurement issues for hours.
Also, if you're buying thermistors for automotive or industrial use, look for the AEC-Q200 qualified versions. That's the automotive passive component standard, and it's a good shortcut for weeding out components that were never designed for harsh environments.
How to Use a Multimeter to Test Voltage (Without Breaking Something)
Most of the multimeter questions I get from our newer engineers are about voltage measurement—not because it's hard, but because the consequences of doing it wrong are immediate and dramatic.
Here's the short version:
- Black probe in the COM jack. Always. That's non-negotiable.
- Red probe in the VΩ jack for voltage and resistance. The high-current jack (usually labeled 10A) is only for measuring current—and only when the dial is set to current mode.
- DC vs AC: use the V with a straight line for DC voltage (batteries, power supplies), and the V with a wavy line for AC (wall outlets, transformers).
- Start high, work down. If the display reads zero on the 600 V range, try a lower range. That's usually a range issue, not a no-voltage issue.
If you've ever blown a multimeter fuse by leaving the probes in the wrong jacks and touching a live circuit—you know the feeling. It happens to everyone once. The trick is to make it happen exactly once.
One detail most guides miss: the multimeter's own battery affects readings, especially in resistance mode. A meter running low on battery will give you inaccurate resistance values. We keep spare 9V batteries in the inspection lab because, honestly, I've been fooled by a dying meter in the middle of a batch inspection. Boring detail. Huge impact.
Why DuraForce Pro 2 and Similar Rugged Devices Raise the Bar
Let me give you a concrete example of why component quality matters in ways your spec sheet won't show you. Take a rugged handheld device—something like the DuraForce Pro 2 that field workers carry. That device is expected to survive high heat, freezing temperatures, drops, and years of rough use.
One of the least glamorous components inside it is the NTC thermistor on the battery pack. Its job is to tell the charging circuit how hot the battery is. If that thermistor drifts even a few percent off spec, the device will either charge too slowly (annoying in the field) or charge the battery hot (dangerous in any setting).
That's the argument I make to our procurement team every time we talk about component costs: a $0.30 thermistor with a 5% failure rate can create a $3,000 warranty claim or worse. In a medical device, that same thermistor could create a much bigger problem than a warranty claim. Context matters.
When Vishay Doesn't Make Sense
To be fair, there are situations where paying the Vishay premium is hard to justify. If you're building a prototype, tinkering on a hobby project, or working on a product where a few percent of drift doesn't matter, buy the cheaper parts. I do it myself when I'm working on weekend projects. A precision foil resistor in an LED blinker circuit is overkill, pure and simple.
I also get why procurement pushes back on premium components. Budgets are real. And during the worst of the chip shortage, certain Vishay lines had lead times past 30 weeks. That's a legitimate constraint, not an excuse.
But the lesson I can't unlearn is that the total cost of a failed batch includes the testing, the downtime, the revalidation, and the lost trust. The $22,000 we lost on that March 2023 batch taught me to think in total cost, not unit price. The cheaper parts weren't cheaper. They were just priced lower.
So maybe the better question isn't "Is Vishay worth it?" It's "What happens if this specific component fails in my specific product?" Your answer to that tells you which components deserve the premium—and which ones are fine to buy on price.