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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.

#wheatstone #bridge #strain-gauge #instrumentation #electronics #developer-tools
api.oanor.com/wheatstone-api
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/api/wheatstone-api/openapi.json
/api/wheatstone-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
90 ms
Server probes · 24h
Subscribers
3,762
active
Total calls
32
last 7 days
status Full status page → · 24 probes/24h

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
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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
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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
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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
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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

Load Cell API

Load-cell (weighing-transducer) maths as an API, computed locally and deterministically. The output endpoint computes the bridge output voltage a strain-gauge load cell produces under a given load, Vout = (load/capacity)·sensitivity·excitation, where the full-scale output FSO = sensitivity(mV/V)·excitation(V) is reached at the rated capacity — it returns the output in millivolts, the equivalent mV/V at that load and the capacity utilization, and flags overload. The load endpoint inverts this to recover the applied load from a measured bridge output, load = (Vout/FSO)·capacity. The array endpoint sizes a multi-cell weighing platform: from the number of identical cells, the per-cell capacity and the live and dead (tare) load it returns the evenly distributed per-cell load, its output and utilization and the total system capacity, so cells can be chosen to stay under capacity in the worst case. Sensitivity is in mV/V, excitation in volts (default 10), output in millivolts; load and capacity share any consistent unit. Everything is computed locally and deterministically, so it is instant and private. Ideal for industrial-weighing, scale, force-measurement, silo and process-control app developers, load-cell sizing and calibration tools, and instrumentation education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is load-cell transducer output; for the underlying Wheatstone-bridge and strain maths use a Wheatstone-bridge API.

api.oanor.com/loadcell-api

Voltage Divider API

Resistive voltage-divider circuit design as an API, computed locally and deterministically. The divide endpoint takes an input voltage and two resistors and returns the output voltage Vout = Vin·R2/(R1+R2), the current I = Vin/(R1+R2) that flows through the chain, and the power dissipated in each resistor and in total — a 12 V source with R1 = 1 kΩ and R2 = 2 kΩ gives 8 V at 4 mA. The loaded endpoint adds a load resistor across R2, computes the parallel combination R2′ = R2·RL/(R2+RL) and the loaded output Vout = Vin·R2′/(R1+R2′), and reports the droop in volts and percent against the unloaded value, the classic mistake when a divider feeds a real load. The resistor endpoint sizes the missing resistor for a target output — R2 = R1·Vout/(Vin−Vout) or R1 = R2·(Vin−Vout)/Vout — so you can pick parts for a reference or sensor-bias point. All quantities are volts, ohms, amps and watts. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, embedded, hardware, sensor-interfacing and EE-education app developers, reference-voltage and bias-network tools, and maker software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the resistive divider; for a single Ohm’s-law relationship use an Ohm’s-law API and for RC/RL filters an RC-filter API.

api.oanor.com/voltagedivider-api

RC Filter API

First-order RC and RL passive-filter design as an API, computed locally and deterministically. The lowpass and highpass endpoints take a resistor and capacitor (RC) or a resistor and inductor (RL) and return the −3 dB cutoff frequency (fc = 1/(2πRC) for RC, R/(2πL) for RL), the time constant (τ = RC or L/R) and the angular cutoff; pass a frequency as well and they add the magnitude response as a linear gain and in decibels and the phase shift in degrees — a 1 kΩ / 1 µF low-pass has fc ≈ 159.15 Hz, and right at the cutoff the gain is −3.01 dB with −45° phase for a low-pass or +45° for a high-pass. The component endpoint solves the missing one of fc, R and C from the other two (fc = 1/(2πRC)), so you can size a resistor or capacitor for a target cutoff. All quantities are SI: ohms, farads, henries and hertz. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, audio, embedded, signal-processing and EE-education app developers, filter-design and circuit-sizing tools, and maker software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is first-order single-pole filter design; for full RLC impedance and resonance use an impedance API and for stored capacitor energy a capacitor API.

api.oanor.com/rcfilter-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.

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Code snippets

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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())

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