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Full changelogEngine 1.18.3

Preferred-Value Synthesiser

Fundamentals

The closest single part, series pair and parallel pair from an E-series, ranked by error.

Inputs

Ω
3.83 kΩ
Ω
Ω
1 MΩ

Results

Best combination

Not judged: E24 parts are only as accurate as their ±5 % tolerance. The error shown is from nominal values.

= 3.832 kΩ, 0.054 % from target
3.9kΩ ∥ 220 kΩ
Nearest single (E24)

1.83 % error
3.9kΩ
All results (1)
Target
3.83kΩ

E24 parts are ±5 %. For better absolute accuracy, use a tighter series rather than a pair.

Ranked candidates
TopologyRaRbResultError
Single3.9 kΩ—3.9 kΩ1.828 %
Series220 Ω3.6 kΩ3.82 kΩ-0.261 %
Series240 Ω3.6 kΩ3.84 kΩ0.261 %
Series820 Ω3 kΩ3.82 kΩ-0.261 %
Series510 Ω3.3 kΩ3.81 kΩ-0.522 %
Parallel3.9 kΩ220 kΩ3.832 kΩ0.054 %
Parallel6.2 kΩ10 kΩ3.827 kΩ-0.074 %
Parallel3.9 kΩ200 kΩ3.825 kΩ-0.120 %
Parallel3.9 kΩ240 kΩ3.838 kΩ0.199 %

Parameter sweep

Vary one input over a range and see the answer and verdict at each step, as a table and a curve.Pro

Worst-case corners

Put a tolerance on each input and get the worst-case band around the answer.Pro

Parts that track move together.Inputs in the same group move together, like a matched pair or parts from one reel. Leave independent parts ungrouped: that is the safe choice.

Give at least one input a tolerance above zero.

Circuit

The principle

Preferred values form a geometric series: each decade of En has n steps of equal ratio, and each series carries a tolerance of roughly half its step. E24 steps about 10 % (±5 %); E96 about 2.4 % (±1 %).

k-th value of series En
Rk=10 k/nk=0,1,…,n−1R_k = 10^{\,k/n} \qquad k = 0,1,\dots ,n-1
Rounded to 2 or 3 significant figures; a few E24 values depart from the formula.
Step ratio
Rk+1Rk=101/n  ⇒  E24: 1.10E96: 1.024\frac{R_{k+1}}{R_k} = 10^{1/n} \;\Rightarrow\; \t{E24: 1.10}\quad \t{E96: 1.024}
Synthesis
Rser=Ra+RbRpar=RaRbRa+RbR_{ser} = R_a + R_b \qquad R_{par} = \frac{R_a R_b}{R_a + R_b}
More detail

When a pair is worth it

  • Worth it where a ratio matters (feedback dividers, gain, timing) and the two parts track: same type, same reel, placed side by side.
  • Not worth it for absolute accuracy: two ±5 % parts still make ±5 %. An E96 1 % part usually costs about the same.
Stocking rule. E24 for non-critical work, E96 1 % thin film for feedback paths. Every extra part is another placement and another joint.
Reference: IEC 60063, preferred number series for resistors and capacitors.

Engine version ⁨1.18.3⁩