query_value
Retrieve a signal's value at a specific time or frequency point from LTspice simulation results, returning the nearest raw data point without interpolation.
Instructions
Look up the value of a signal at a specific time point (transient) or frequency (AC). Returns the nearest data point without interpolation.
To pick a step of a .step/.DC sweep by its axis VALUE (rather than a raw step index), pass step_axis + step_value (e.g. step_axis='temp', step_value='27'); at then selects the inner-axis point within that step (optional). AC samples also return magnitude_linear alongside magnitude_db/phase_deg.
To query a run of a completed sweep/MC job, pass job_id + run_index instead of raw_file — the run is analyzed like any standalone raw.
This is one signal at one point (signal=). For many signals, or a whole waveform over a window, use export_waveform (signals=).
If the run hit a run-level solve failure (singular matrix / non-convergence), that simulator line is relayed into warnings — the value is still returned, but the whole solve is suspect, so read it.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| at | No | Time or frequency to query in SPICE notation (e.g., '1m', '100u', '1G', '2.5k'). Required unless ``step_axis`` is given (then it picks the inner-axis point within the chosen step; optional). | |
| step | No | Step index for .step directives (ignored when ``step_axis`` is used). | |
| format | No | Response format: 'json' for structured data, 'text' for human-readable | |
| job_id | No | Analyze a specific run of a completed sweep/MC (or single) job instead of a raw_file path; pair with ``run_index``. Lets you query a sweep run the same way you'd query a standalone raw. | |
| signal | Yes | Signal/trace name (e.g., 'V(out)', 'I(R1)'), or a device operating-point shorthand for an ngspice .save'd parameter: 'm1.gm' / 'm1.vth' (resolves to '@m1[gm]', incl. subcircuit paths like 'x1.m1.gm'). | |
| raw_file | No | Path to .raw result file. Pass this OR ``job_id`` (a job run), not both. | |
| run_index | No | 0-based run to analyze when ``job_id`` is given (default 0). | |
| step_axis | No | Select the step by a .step/.DC sweep-axis VALUE instead of an index: the parameter name (e.g. 'temp', 'Rval'). Pair with ``step_value``. The nearest step is chosen and flagged with ``exact_match``. | |
| step_value | No | Target value of ``step_axis`` in SPICE notation (e.g. '27', '1k'). Required when ``step_axis`` is given. |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
| axis | No | ||
| unit | No | ||
| value | No | ||
| signal | No | ||
| actual_x | No | ||
| warnings | No | ||
| actual_at | No | ||
| phase_deg | No | ||
| step_index | No | ||
| exact_match | No | ||
| requested_x | No | ||
| actual_value | No | ||
| magnitude_db | No | ||
| requested_at | No | ||
| requested_value | No | ||
| magnitude_linear | No |