10kΩ NTC Thermistor (Beta 3435)
An older, still widely-stocked NTC thermistor standard whose shallower beta-3435 curve makes it common in legacy industrial and HVAC thermostat designs, distinct from the steeper beta-3950 parts favored in newer 3D-printer firmware.
How this component works
A thermistor is a special type of resistor whose electrical resistance changes significantly with temperature. They come in two primary types: NTC (Negative Temperature Coefficient), where resistance drops as it gets hotter, and PTC (Positive Temperature Coefficient), where resistance rises as it gets hotter.
NTC thermistors are incredibly common as cheap, robust temperature sensors in 3D printers, digital thermostats, and battery charging circuits. They are highly non-linear, so converting their resistance into a precise Celsius temperature reading requires solving a complex logarithmic equation (the Steinhart-Hart equation) in software.
Deep Dive: 10kΩ NTC (B3435)
Running the same beta-equation approximation used for the B3950 sibling entry, but with B = 3435 instead: at 100°C (373.15K), the exponent term B×(1/T − 1/T0) works out to roughly −2.32, and exp(−2.32) ≈ 0.099, giving R(100°C) ≈ 990Ω — noticeably higher than the B3950 part's roughly 700Ω at the same real temperature, despite both parts sharing the identical 10kΩ nominal rating at 25°C. That gentler slope means less resistance change per degree of temperature rise, translating to lower resolution if the same measurement circuit and ADC are used for both.
Despite the resolution disadvantage, beta 3435 remains extremely common because it predates the newer 3950 standard's popularity and is deeply embedded in HVAC thermostats, older industrial temperature-control equipment, and the replacement-parts ecosystems built around them. A designer maintaining or repairing an existing product line built around a B3435 sensor generally has strong reasons to keep using that same beta value — component sourcing, calibration tables, and firmware already assume it — even in a case where a fresh, ground-up design targeting maximum sensitivity (like a 3D-printer hotend) would likely choose the steeper B3950 curve instead.
Common Use Cases
- HVAC thermostat temperature sensing where the sensor operates mostly within a narrower room-temperature-adjacent range
- Legacy appliance and industrial control designs standardized around this widely-available beta value
- General-purpose temperature sensing where a gentler resistance curve across a moderate range is acceptable
Frequently Asked Questions
How does this thermistor's curve compare numerically to the beta-3950 entry in this category?
At 100°C, this B3435 part's resistance works out to roughly 990Ω (about a 10x drop from its 10kΩ nominal value at 25°C), compared to roughly 700Ω (a 14x drop) for the B3950 part — a meaningfully shallower curve at the same nominal 25°C resistance.
If beta 3950 gives more temperature resolution, why is beta 3435 still commonly used?
It remains a long-established industry standard, especially in HVAC and older industrial equipment, where existing lookup tables, replacement-part stocking, and design libraries are already built around it — switching an established product line to a different beta value has its own cost even where 3950 might technically offer sharper resolution.
Is a shallower beta curve ever actually preferable?
It can behave more predictably across a wider or more moderate range in some designs, and because it is such a long-established standard, replacement parts and reference data are broadly available — useful when designing for compatibility with an existing installed base rather than maximizing sensitivity in a narrow range.
Comparison Notes
Compared to the B3950 entry in this category, this part's lower beta value gives a gentler resistance-vs-temperature slope — less sensitive per degree, but consistent with a long-established industrial and HVAC standard that many existing designs and lookup tables already assume.