[_benj]

There’s also part of, good designs don’t depend on high precision components. I think TAoE emphasized that. For high precision one can use trim potentiometers or maybe even digital potentiometer with an ADC at the other side to measure and get as close as possible, but otherwise depending on resistors for high precision is kinda rough (I’m think like an RC circuit that need a very specific resistance to meet some specific timing requirements)

[picture]

High precision resistors are often necessary for metrology applications like very precise and low drift voltage sources. Often parts like Vishay's same-substrate thin film resistor networks [0] are used, as the temperature of each resistor leg are kept the closely relative to each other, resulting in the ratio between them being stable against temperature changes. Even if you use some adjustable/tunable circuit, you usually still require some sort of precision resistor network as an original standard.

In general, however, it's much better to measure/sense physical phenomenon by first converting it into frequency, because it is much easier to measure frequency precisely. Using something like a TCXO from Seiko Epson with 1 ppm tolerance, and measuring over time, you can easily achieve 0.00001% precision and beyond. I know that strain gauges used in civil engineering often utilize this concept, where a metal string is "plucked" electronically and the frequency is then measured.

[0] https://www.vishay.com/docs/61010/ccc.pdf and https://foilresistors.com/docs/63120/hzseries.pdf

[SAI_Peregrinus]

On the frequency note, the primary standards for voltage are superconducting quantum Josephson junction arrays; basically fancy frequenvy-to-voltage converters.

[contingencies]

Neat. Next time I see resistors in a splayed or star configuration with one leg in shared proximity I will think of this comment.

[segfaultbuserr]

> There’s also part of, good designs don’t depend on high precision components. I think TAoE emphasized that.

If I call correctly, TAoE said engineering calculations should never keep too many significant digits, since no real-world components are that accurate, and all good designs should keep component tolerance in mind - they should not have an unrealistic expectation of precision. It also mentioned that designing a circuit for absolute worst-case tolerance is often a waste of time.

But I don't think TAoE told you to "avoid precision components in your design, use trimmers instead" (Do you have a page number?) when the application calls for it. For example, 0.1% feedback resistors in precision voltage references are often reasonable.

> For high precision one can use trim potentiometers

From what I've read (from other sources), mechanical trimmer used to be extremely popular, but they went out of favor in recent decades because tuning could not be automated and that increased assembly cost. Using a 0.1% resistor is favorable if it allows trim-free production.

> or maybe even digital potentiometer with an ADC at the other side to measure and get as close as possible

Yes, digital trimming and calibrations is today's go-to solution.

[gnramires]

It's not always possible to design avoiding precision components though (although as you mentioned trim components could fit the bill). If you want to precisely measure current with a shunt resistor for example, you need high precision (although you can also calibrate it digitally). More than precision, which can sometimes be calibrated against, there are also various kinds of environmental stabilities that may be more important: temperature stability, pressure stability, etc. -- you'd need other forms of calibration, measurement and compensation.

Also, component-level precision has limits because eventually trace impedance starts to be significant (hence the use of trim components you mentioned!).

Youtuber Marco Reps goes through various high precision equipment that often have precision resistors and such, recommended if interested!