LTspice .MEASURE SQLite Database Reference

Structure and usage of the .db file generated by .MEAS statements.

Overview

When a simulation includes .MEAS statements, LTspice saves the results to an SQLite database file with a .db extension (same base name as the schematic/netlist). This database is particularly useful when combined with .STEP parameter sweeps, as it captures measurement results across all sweep values in a queryable format.

If there are no .STEP parameters being swept, the Parameters and Steps tables will be empty.

Database Schema

The database contains five tables: schema, Parameters, Steps, Measurements, and Results.

Table Relationships

Parameters (1) ──── (many) Steps
     │                        │
     │                        │ Step
     │                        ▼
Measurements (1) ──── (many) Results

Each parameter has multiple step values (one per sweep point)
Each measurement has multiple results (one per step)
Results are linked to Steps via the Step column
Results are linked to Measurements via the ID column

schema

Column	Type	Description
version	TEXT	Database schema version (e.g., “1.0”)

Parameters

Column	Type	Description
Key	INTEGER (PK)	Unique identifier for each stepped parameter
Name	TEXT	The `.step` item name (e.g., “css”, “r1”). Stored in lowercase (casefolded).

Steps

Column	Type	Description
Step	INTEGER (PK)	Step number (1-based)
Key	INTEGER (PK)	FK → Parameters.Key
Value	REAL	The parameter value for this step

Measurements

Column	Type	Description
ID	INTEGER (PK)	Unique identifier for each `.MEAS` statement
Name	TEXT	The measurement name from `.meas <name>`. Stored in lowercase (casefolded).
Expression	TEXT	The measurement expression from `.meas <expr>`
Type	INTEGER	Measurement type (see below)
Complex	INTEGER	`0` = real result, `1` = complex result
Format	INTEGER	Complex data representation: `1` = Polar, `2` = Cartesian, `3` = Bode
Digits	INTEGER	Currently not used

Measurements.Type values:

Type	Meaning	Example
0	Parameter calculation	`.meas PARAM res PARAM 3*val1/val2`
1	Point measurement (FIND)	`.meas TRAN res FIND V(out) AT=5m`
2	Range measurement	`.meas TRAN res AVG V(out) TRIG ... TARG ...`
3	WHEN measurement (abscissa)	`.meas TRAN res WHEN V(out)=4.8`

Results

IMPORTANT: The Results table does NOT have a Value column. The measured result is stored in different columns depending on the measurement type.

Column	Type	Description
ID	INTEGER	FK → Measurements.ID
Step	INTEGER	FK → Steps.Step
Re	REAL	Real part of the measured ordinate value (used by FIND, AVG, MAX, MIN, PP, RMS, INTEG, PARAM)
Im	REAL	Imaginary part of the measured ordinate value (non-NULL only when Measurements.Complex = 1)
FROM	REAL	Range measurement abscissa starting point (TRIG value)
TO	REAL	Range measurement abscissa ending point (TARG value)
AT	REAL	Point/WHEN measurement abscissa value — the value on the horizontal axis (e.g., time or frequency) where a condition is met
Success	INTEGER	`0` = measurement failed (condition never met), `1` = measurement succeeded

Which Results Column Contains the Answer?

Measurement type	Result column(s)	Explanation
`WHEN V(out)=4.8` (no FIND)	AT	Returns the abscissa value (e.g., time) when the condition is met
`FIND V(out) WHEN ...`	Re (and Im if complex)	Returns the ordinate value at the condition point
`FIND V(out) AT=5m`	Re (and Im if complex)	Returns the ordinate value at the specified point
`AVG`, `MAX`, `MIN`, `PP`, `RMS`, `INTEG`	Re (and Im if complex); FROM and TO for the range	Returns the computed value over the interval
`PARAM expr`	Re	Returns the computed parameter expression value
TRIG/TARG (no operation keyword)	Re	Returns the abscissa distance between TRIG and TARG

Querying the Database

View Results with Step Values

To display step values alongside results, use an INNER JOIN:

SELECT Results.*, Steps.Value AS Step_value
FROM Steps
INNER JOIN Results ON Results.Step = Steps.Step

Create a Temporary View for Plotting

CREATE TEMP VIEW Resultswsteps AS
SELECT Results.*, Steps.Value AS Step_value
FROM Steps
INNER JOIN Results ON Results.Step = Steps.Step

Accessing the Database

The .db file can be opened with any SQLite-compatible tool:

DB Browser for SQLite
Python (sqlite3 module)
Command-line sqlite3

Python Example

import sqlite3

conn = sqlite3.connect("my_circuit.db")
cursor = conn.cursor()

# Get all measurement results with step values
cursor.execute("""
    SELECT Results.*, Steps.Value AS Step_value
    FROM Steps
    INNER JOIN Results ON Results.Step = Steps.Step
""")

for row in cursor.fetchall():
    print(row)

conn.close()

Extracting Values by Measurement Type

The correct Results column to use depends on the .MEAS type. Check the Measurements table to determine which column holds the result.

import sqlite3

conn = sqlite3.connect("my_circuit.db")
cursor = conn.cursor()

# 1. Check what measurements exist and their types
cursor.execute("SELECT ID, Name, Type FROM Measurements")
for m in cursor.fetchall():
    print(f"  ID={m[0]}, Name={m[1]}, Type={m[2]}")
    # Type 0 = PARAM, 1 = FIND, 2 = Range, 3 = WHEN

# 2. For a WHEN measurement (Type=3), the result is in the AT column:
#    .meas TRAN Trise WHEN V(OUT)=4.8
cursor.execute("""
    SELECT Steps.Value AS step_val, Results.AT AS meas_result
    FROM Steps
    INNER JOIN Results ON Results.Step = Steps.Step
    WHERE Results.ID = 1 AND Results.Success = 1
""")

# 3. For a FIND or range measurement (Type=1 or 2), use Re (and Im if complex):
#    .meas TRAN res FIND V(out) AT=5m
#    .meas TRAN res AVG V(out)
cursor.execute("""
    SELECT Steps.Value AS step_val, Results.Re AS meas_result
    FROM Steps
    INNER JOIN Results ON Results.Step = Steps.Step
    WHERE Results.ID = 1 AND Results.Success = 1
""")

conn.close()