Resistor Standard

{
  "above": 4700,
  "asOf": "2026-10-11T08:33:13.043Z",
  "below": 3900,
  "closest": 3900,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "errorPct": 9.30233,
  "isStandard": false,
  "notChecked": [
    "tolerance matching: E12 parts are 10% typically, E24 5% and E96 1%",
    "series availability for a given power rating or package",
    "…1 more"
  ],
  "otherSeries": [
    {
      "closest": 4700,
      "errorPct": 9.302,
      "series": "E6"
    },
    {
      "closest": 4300,
      "errorPct": 0,
      "series": "E24"
    }
  ],
  "reasons": [
    "E12 has 12 values per decade.",
    "Tighter series (E48 and up) are 2% or better parts and cost more."
  ],
  "series": "E12",
  "source": "computed locally",
  "summary": "4.3 kohm in E12: closest 3.9 kohm (9.3% off); below 3.9 kohm, above 4.7 kohm.",
  "target": 4300,
  "verdict": "NEAREST_FOUND"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://electronics-calc.x402tookit.com/resistor-standard?series=E12&target=4.3k'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://electronics-calc.x402tookit.com/resistor-standard?series=E12&target=4.3k' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Felectronics-calc.x402tookit.com%2Fresistor-standard
const res = await pay("https://electronics-calc.x402tookit.com/resistor-standard?series=E12&target=4.3k");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://electronics-calc.x402tookit.com/resistor-standard?series=E12&target=4.3k")
    print(res.status_code, res.text)