Source: https://guthlabs.ai/docs/instruments/shot-noise-calculator/mechanism/

instrument mechanism / verified-clean

# Shot Noise Calculator mechanism

The inspectable method record for Shot Noise Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

Formula verification passes under the explicit assumptions of ideal Poisson shot noise, positive current magnitude, q in coulombs, current in amperes, bandwidth in hertz, and one-sided equivalent noise bandwidth. NEEDS_REVIEW is required because the spec does not define the current-sign handling or the one-sided versus two-sided bandwidth convention.

- In = sqrt(2qIΔf) is the standard ideal-Poisson shot-noise RMS formula when I is the nonnegative current magnitude and Δf is a one-sided equivalent noise bandwidth.

- The spec does not state whether a signed DC current is accepted; using a negative I makes the square-root argument invalid. The implementation must either use abs(I) or reject negative input.

- The bandwidth convention is unspecified. The factor 2 corresponds to the usual one-sided shot-noise spectral density; a two-sided bandwidth convention can introduce a factor-of-two ambiguity.

- The formula describes ideal shot noise only, not total junction noise; practical junctions may require a Fano factor or additional noise terms.

## Units and conventions

- q = 1.602176634e-19 C exactly (elementary charge).

- I must be converted to amperes (A).

- Δf must be converted to hertz (Hz), interpreted as one-sided equivalent noise bandwidth.

- The output In is RMS current in amperes (A rms).

- The input current magnitude and bandwidth must both be nonnegative.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "DC_current": "1 mA",
    "bandwidth": "1 kHz",
    "q_C": 1.602176634e-19
  },
  "expected_outputs": {
    "In_rms_A": 5.6607007e-10
  },
  "working": "Convert units: I = 1e-3 A and Δf = 1e3 Hz. Compute 2qIΔf = 2 × 1.602176634e-19 × 1e-3 × 1e3 = 3.204353268e-19 A². Therefore In = sqrt(3.204353268e-19) = 5.6607007e-10 A rms."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification does not define validation behavior for negative current or bandwidth, and it does not state whether a signed reverse current should be rejected or converted to its magnitude. Without those rules, invalid inputs can produce undefined square roots or convention-dependent results.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/shot-noise-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/shot-noise-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/shot-noise-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`