Solve the balancing arm
API · /wheatstone-api
Wheatstone Bridge API
healthy
3,762 Subscribers
Wheatstone-bridge and strain-gauge maths as an API, computed locally and deterministically. The bridge endpoint takes the four arm resistances R1–R4 and an excitation voltage and returns the bridge output voltage between the two midpoints, Vout = Vin·(R2/(R1+R2) − R4/(R3+R4)), in volts and millivolts, the voltage at each midpoint, and whether the bridge is balanced (Vout = 0 when R1·R4 = R2·R3). The balance endpoint inverts it: give any three arms and it solves the fourth resistance that balances the bridge, the classic way a Wheatstone bridge measures an unknown resistance. The strain endpoint models a strain-gauge bridge — quarter, half or full — and converts in both directions between mechanical strain and electrical output: from a gauge factor and a strain (given directly, as microstrain or as a relative resistance change ΔR/R = GF·ε) it returns the output ratio and voltage Vout/Vin = (k/4)·GF·ε where k is the number of active arms, and from an output voltage and excitation it returns the strain and microstrain. Everything is computed locally and deterministically, so it is instant and private. Ideal for instrumentation and sensor tools, load-cell, pressure-sensor and RTD measurement design, strain-gauge and data-acquisition apps, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is bridge and strain-gauge measurement; for Ohm's law, voltage dividers and series/parallel resistor combinations use an Ohm's-law API.
api.oanor.com/wheatstone-api
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 75 ms
- Server probes · 24h
- Subscribers
- 3,762
- active
- Total calls
- 80
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 2,000 calls / month
- 2 requests / second
- Hard cap (429 above quota, no overage)
- Bridge output voltage from R1-R4 + excitation
- Balanced-bridge detection
- JSON in/out, no key for first 2k calls
Starter
€9.00 /month
- 25,000 calls / month
- 8 requests / second
- Hard cap (429 above quota, no overage)
- Quarter/half/full-bridge strain-gauge maths
- Gauge-factor + microstrain conversion
- Deterministic, sub-millisecond responses
- Email support
Pro
€24.00 /month
- 150,000 calls / month
- 25 requests / second
- Hard cap (429 above quota, no overage)
- Bulk arm-resistance sweeps
- Temperature-compensation terms
- Bridge sensitivity + linearity output
- Priority support, 99.9% uptime
Mega
€74.00 /month
- 769,000 calls / month
- 80 requests / second
- Hard cap (429 above quota, no overage)
- High-throughput instrumentation pipelines
- Full strain + Wheatstone suite, all bridge configs
- Highest rate limits for sensor data streams
- Dedicated SLA + priority engineering support
Built by
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api.oanor.com/wormhole-api
Across Bridge API
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api.oanor.com/across-api
RTD Pt100 Sensor API
RTD (resistance-temperature-detector) sensor maths as an API, computed locally and deterministically with the IEC 60751 Callendar–Van Dusen equation — the resistance, temperature and tolerance numbers an instrumentation or controls engineer reads a Pt100 or Pt1000 with. The resistance endpoint gives the sensor resistance from temperature: above 0 °C, R = R₀·(1 + A·T + B·T²) with A = 3.9083×10⁻³ and B = −5.775×10⁻⁷; below 0 °C a third term adds C·(T−100)·T³ — a standard Pt100 (100 Ω at 0 °C) reads 138.51 Ω at 100 °C and 80.31 Ω at −50 °C, and a Pt1000 is ten times that. The temperature endpoint inverts it to turn a measured resistance back into temperature — analytically above 0 °C, iteratively below — exactly what a transmitter does with the bridge reading, and a reminder that a 3- or 4-wire connection cancels the lead-wire resistance so it does not read as extra degrees. The tolerance endpoint gives the IEC 60751 accuracy band in both °C and Ω by class — AA ±(0.10 + 0.0017·|T|), A ±(0.15 + 0.002·|T|), B ±(0.30 + 0.005·|T|), C ±(0.60 + 0.010·|T|) — the error growing with distance from 0 °C. Everything is computed locally and deterministically, so it is instant and private. Ideal for instrumentation and controls software, data-logger and transmitter firmware, calibration and industrial-IoT tools. Pure local computation — no key, no third-party service, instant. 3 compute endpoints. For NTC thermistors use a thermistor API; for thermocouples a thermocouple API.
api.oanor.com/rtd-api
Thermocouple API
Type-K thermocouple temperature/voltage conversion as an API, computed locally and deterministically from the official NIST ITS-90 reference functions. The voltage endpoint converts a junction temperature in °C to the thermo-electromotive force in millivolts using the NIST type-K direct polynomial (with its Gaussian correction term above 0 °C), and performs cold-junction compensation by subtracting the reference-junction EMF, so a hot junction at 200 °C against a 25 °C terminal block gives the EMF your meter actually reads; a type-K junction produces 4.096 mV at 100 °C and 41.276 mV at 1000 °C against a 0 °C reference. The temperature endpoint does the inverse: it takes the measured EMF in millivolts and the reference-junction temperature, refers the reading back to 0 °C by adding the cold-junction EMF, and returns the hot-junction temperature in °C and K — obtained by numerically inverting the same monotonic forward polynomial, so it is exactly consistent with the forward conversion. Type K (chromel–alumel) covers −270 to 1372 °C. Everything is computed locally and deterministically, so it is instant and private. Ideal for industrial-automation, process-control, data-acquisition, IoT-sensor, furnace and lab-instrument app developers, sensor-linearization and cold-junction-compensation tools, and embedded firmware. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 2 endpoints. This is the type-K thermocouple; for resistance-temperature detectors use an RTD/PT100 API.
api.oanor.com/thermocouple-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for Wheatstone Bridge API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Wheatstone Bridge API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Wheatstone Bridge API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Wheatstone Bridge API cost?
Wheatstone Bridge API has a free tier with 100 calls / month. Paid plans start at €9.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Wheatstone Bridge API GDPR-compliant?
All requests to Wheatstone Bridge API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.
Pick an endpoint from the list on the left to see its details and try it.
Code snippets
Sign up to get an API key, then call any path under your slug.
curl https://api.oanor.com/wheatstone-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."const res = await fetch("https://api.oanor.com/wheatstone-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();$ch = curl_init("https://api.oanor.com/wheatstone-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);import requests
r = requests.get(
"https://api.oanor.com/wheatstone-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())Ratings
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