.MEAS / .MEASURE Statement

The .MEAS (or .MEASURE) statement extracts a single scalar number from simulation waveform data — for example, "how long does the output take to rise from 1 V to 9 V?", "what is the average voltage?", or "what is the RMS current?". Both .MEAS and .MEASURE are interchangeable.

General Syntax

.MEAS <analysis_type> <name> <measurement_spec>
.MEASURE <analysis_type> <name> <measurement_spec>

Field	Meaning	Values
`analysis_type`	Which simulation type to measure	`TRAN`, `AC`, `DC`, `OP`, `NOISE`
`name`	A label you choose — this is the key used to look up the result in C#	Any identifier (e.g. `rise_time`, `vmax`)
`measurement_spec`	What to measure and how (described in detail below)	One of the 12 measurement types

Quick Reference — All Measurement Types

Type	What It Returns	Read More
`TRIG … TARG`	Time (or sweep) difference between two threshold crossings	TRIG/TARG
`WHEN`	Time (or sweep value) at which a signal crosses a threshold	WHEN
`FIND … WHEN`	Value of signal A at the moment signal B crosses a threshold	FIND/WHEN
`FIND … AT`	Value of a signal at a specific point on the abscissa	FIND/AT
`MAX`	Maximum value of a signal	MAX
`MIN`	Minimum value of a signal	MIN
`AVG`	Time-weighted average (trapezoidal mean)	AVG
`RMS`	Root mean square	RMS
`PP`	Peak-to-peak (max − min)	PP
`INTEG`	Trapezoidal integral	INTEG
`DERIV`	Derivative at a single point	DERIV
`PARAM`	Evaluate an arithmetic expression using other measurement results	PARAM

Common Qualifiers

These qualifiers can be combined with most measurement types:

Qualifier	Meaning	Example
`VAL=<v>`	Threshold voltage/current value	`VAL=5.0`
`RISE=<n>`	Match the nth rising crossing	`RISE=1` (first rising edge)
`RISE=LAST`	Match the last rising crossing	`RISE=LAST`
`FALL=<n>`	Match the nth falling crossing	`FALL=2` (second falling edge)
`FALL=LAST`	Match the last falling crossing	`FALL=LAST`
`CROSS=<n>`	Match the nth crossing in either direction	`CROSS=3`
`CROSS=LAST`	Match the last crossing in either direction	`CROSS=LAST`
`TD=<time>`	Ignore data before this time (start searching later); works with TRIG/TARG and WHEN/FIND	`TD=5u`
`FROM=<x>`	Start of the measurement window	`FROM=2u`
`TO=<x>`	End of the measurement window	`TO=8u`
`AT=<x>`	Evaluate at a specific point (used in DERIV and FIND)	`AT=5u`

Measurement Types In Detail

TRIG/TARG — Timing Measurements

Purpose: Measure the elapsed time (or sweep distance) between two events — a trigger threshold crossing and a target threshold crossing. This is ideal for rise time, fall time, and propagation delay.

How it works:

The simulator scans the waveform for the point where the TRIG signal crosses its VAL (the "start" event).
Then it continues scanning for the point where the TARG signal crosses its VAL (the "end" event).
The result is time_of_target − time_of_trigger.

Syntax:

.MEAS <analysis> <name> TRIG <signal> VAL=<v> [RISE|FALL|CROSS=<n>|LAST] [TD=<t>]
+                       TARG <signal> VAL=<v> [RISE|FALL|CROSS=<n>|LAST] [TD=<t>]

Example 1 — Rise time of an RC circuit

An RC circuit charges from 0 V toward 10 V. We measure how long it takes to go from 1 V to 9 V:

* RC circuit rise time
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

* Measure: time from V(OUT)=1V (first rise) to V(OUT)=9V (first rise)
.MEAS TRAN rise_time TRIG V(OUT) VAL=1.0 RISE=1 TARG V(OUT) VAL=9.0 RISE=1
.END

Expected result: ~21.97 ms (RC time constant = 10 kΩ × 1 µF = 10 ms; analytically $\tau \ln(9/1) \approx 21.97$ ms).

Example 2 — Propagation delay between input and output

A pulse drives an RC filter. We measure the delay between the input reaching 2.5 V and the output reaching 2.5 V:

* Propagation delay through RC filter
V1 IN 0 PULSE(0 5 0 1n 1n 100u 200u)
R1 IN MID 1k
C1 MID 0 10n
.IC V(MID)=0.0
.TRAN 1e-8 50e-6

* How long after V(IN) hits 2.5V does V(MID) hit 2.5V?
.MEAS TRAN tpd TRIG V(IN) VAL=2.5 RISE=1 TARG V(MID) VAL=2.5 RISE=1
.END

Example 3 — Fall time with FALL qualifier

Swap RISE for FALL to measure falling-edge timing:

* Fall time measurement
V1 IN 0 PULSE(10 0 10e-3 1n 1n 50e-3 100e-3)
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=10.0
.TRAN 1e-5 70e-3

* Time from V(OUT)=9V falling to V(OUT)=1V falling
.MEAS TRAN fall_time TRIG V(OUT) VAL=9.0 FALL=1 TARG V(OUT) VAL=1.0 FALL=1
.END

Example 4 — Using CROSS to match any edge direction

CROSS=n counts crossings regardless of direction (rising or falling). Useful for measuring a half-period of a repeating signal:

* Half-period of a square wave using CROSS
V1 OUT 0 PULSE(0 5 0 1n 1n 10e-6 20e-6)
R1 OUT 0 1k
.TRAN 1e-8 60e-6

* Time between the 2nd and 3rd crossing of 2.5V (= half the period)
.MEAS TRAN t_between TRIG V(OUT) VAL=2.5 CROSS=2 TARG V(OUT) VAL=2.5 CROSS=3
.END

Expected result: ~10 µs (half of the 20 µs period).

Example 5 — Using TD to delay the search start

TD (time delay) tells the simulator to skip early data. The TRIG event will only be found after TD has elapsed:

* Skip the first 5ms before searching for the trigger
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN delayed TRIG V(OUT) VAL=1.0 RISE=1 TD=5e-3 TARG V(OUT) VAL=9.0 RISE=1
.END

WHEN — Threshold Crossing Time

Purpose: Find the time (or frequency, or sweep value) at which a signal crosses a given threshold. Returns a single x-axis value.

How it works: The simulator scans the waveform looking for the point where the signal equals the threshold. Linear interpolation is used between data points for precision.

Syntax — two forms:

* Combined syntax: signal=value in one expression
.MEAS <analysis> <name> WHEN <signal>=<value> [RISE|FALL|CROSS=<n>|LAST] [TD=<t>]

* Separate syntax: signal and VAL as separate tokens
.MEAS <analysis> <name> WHEN <signal> VAL=<value> [RISE|FALL|CROSS=<n>|LAST] [TD=<t>]

Both forms produce the same result.

Example 1 — When does V(OUT) reach 5 V?

* Simple RC charge — find time to reach 50%
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN t50 WHEN V(OUT)=5.0
.END

Expected result: ~6.93 ms ($\tau \ln 2 = 10\text{ms} \times 0.693$).

Example 2 — Second rising crossing of a square wave

For periodic signals, RISE=2 skips the first rising crossing and returns the second:

* 20µs square wave — find the start of the 2nd rising edge
V1 OUT 0 PULSE(0 5 0 1n 1n 10e-6 20e-6)
R1 OUT 0 1k
.TRAN 1e-8 60e-6

.MEAS TRAN t_rise2 WHEN V(OUT)=2.5 RISE=2
.END

Expected result: ~20 µs (second period begins).

Example 3 — First falling crossing

* Find the time of the first falling edge
V1 OUT 0 PULSE(0 5 0 1n 1n 10e-6 20e-6)
R1 OUT 0 1k
.TRAN 1e-8 60e-6

.MEAS TRAN t_fall1 WHEN V(OUT)=2.5 FALL=1
.END

Expected result: ~10 µs.

Example 4 — Using TD to skip early crossings

TD (time delay) works with WHEN just as it does with TRIG/TARG. Only crossings after TD are counted:

* Sine wave crosses 0V many times. With TD=0.8ms, skip crossings before 0.8ms
V1 OUT 0 SIN(0 1 1e3)
R1 OUT 0 1k
.TRAN 1e-6 5e-3

.MEAS TRAN t_first WHEN V(OUT)=0 CROSS=1
.MEAS TRAN t_after_td WHEN V(OUT)=0 CROSS=1 TD=0.8m
.END

Result: t_first is the first crossing (~0.5 ms), while t_after_td is the first crossing after 0.8 ms (~1 ms).

Example 5 — Finding the LAST crossing

Use CROSS=LAST, RISE=LAST, or FALL=LAST to find the final matching crossing in the simulation data:

* Find the last time V(OUT) crosses 0V
V1 OUT 0 SIN(0 1 1e3)
R1 OUT 0 1k
.TRAN 1e-6 5e-3

.MEAS TRAN t_last WHEN V(OUT)=0 CROSS=LAST
.END

Result: t_last is near 5 ms (the last zero crossing before end of simulation).

Example 6 — What happens when the signal never crosses the threshold?

If the threshold is never reached, the measurement result has Success = false and Value = NaN:

* V(OUT) is constant at 5V — it never reaches 10V
V1 OUT 0 5.0
R1 OUT 0 1k
.TRAN 1e-7 10e-6

.MEAS TRAN impossible WHEN V(OUT)=10.0
.END

Result: Success = false, Value = NaN.

FIND/WHEN — Value at a Threshold Crossing

Purpose: Find the value of signal A at the exact moment signal B crosses a threshold. This combines FIND (what to measure) with WHEN (the triggering condition).

How it works:

Scan for the time when the WHEN signal crosses its threshold (same as a regular WHEN measurement).
At that time, read the value of the FIND signal using linear interpolation.
Return that value.

Syntax:

.MEAS <analysis> <name> FIND <signal_A> WHEN <signal_B>=<value> [RISE|FALL|CROSS=<n>|LAST] [TD=<t>]

Example 1 — Output voltage when input crosses 2.5 V

A pulse drives an RC filter. We want to know V(OUT) at the moment V(IN) crosses 2.5 V:

* What is V(OUT) when V(IN) first crosses 2.5V?
V1 IN 0 PULSE(0 5 0 1e-6 1e-6 10e-6 20e-6)
R1 IN OUT 1k
C1 OUT 0 10n
.IC V(OUT)=0.0
.TRAN 1e-8 30e-6

.MEAS TRAN vout_at_cross FIND V(OUT) WHEN V(IN)=2.5
.END

Expected result: A value between 0 V and 5 V (V(OUT) lags V(IN) due to the RC filter).

Example 2 — Find current through a resistor when voltage reaches a threshold

* What is I(R1) when V(OUT) reaches 5V?
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN i_at_5v FIND I(R1) WHEN V(OUT)=5.0
.END

Example 3 — Using RISE=2 to pick a specific crossing

* Find V(OUT) at the 2nd rising crossing of V(IN)
V1 IN 0 PULSE(0 5 0 1n 1n 10e-6 20e-6)
R1 IN OUT 1k
C1 OUT 0 10n
.IC V(OUT)=0.0
.TRAN 1e-8 60e-6

.MEAS TRAN v_at_rise2 FIND V(OUT) WHEN V(IN)=2.5 RISE=2
.END

FIND/AT — Value at a Specific Point

Purpose: Find the value of a signal at a specific point on the abscissa (e.g., a specific time in a transient analysis, or a specific frequency in an AC analysis). The signal value is computed via linear interpolation between data points.

Syntax:

.MEAS <analysis> <name> FIND <signal> AT=<value>

Example 1 — Voltage at a specific time

* RC charge — what is V(OUT) at t=5ms?
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN v_at_5ms FIND V(OUT) AT=5m
.END

Expected result: ~3.935 V ($10 \times (1 - e^{-5/10}) \approx 3.935$).

Example 2 — Constant voltage check

* Constant 5V — FIND AT any time returns 5V
V1 OUT 0 5.0
R1 OUT 0 1k
.TRAN 1e-4 10e-3

.MEAS TRAN v_check FIND V(OUT) AT=5m
.END

Expected result: 5.0 V.

MAX — Maximum Value

Purpose: Find the largest value a signal reaches during the simulation (or within a FROM/TO window).

* RC charge toward 10V — MAX should approach 10V
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN vmax MAX V(OUT)
.END

Expected result: > 9.9 V (the capacitor nearly fully charges in 50 ms = 5τ).

With a window — only consider data between 5 µs and 15 µs:

.MEAS TRAN vmax_window MAX V(OUT) FROM=5e-6 TO=15e-6

MIN — Minimum Value

Purpose: Find the smallest value a signal reaches.

* RC charge from 0V — MIN is the starting value
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN vmin MIN V(OUT)
.END

Expected result: < 0.1 V (the initial voltage near 0 V).

AVG — Average Value

Purpose: Compute the time-weighted average of a signal using trapezoidal integration:

$$\text{AVG} = \frac{1}{t_{\text{end}} - t_{\text{start}}} \int_{t_{\text{start}}}^{t_{\text{end}}} V(t) , dt$$

Example 1 — DC voltage across a resistor divider

A voltage divider creates a steady 5 V at node MID. The average should equal 5 V:

* Resistor divider: V(MID) = 10V * 10k / (10k + 10k) = 5V
V1 IN 0 10.0
R1 IN MID 10k
R2 MID 0 10k
.TRAN 1e-7 10e-6

.MEAS TRAN vavg_dc AVG V(MID)
.END

Expected result: 5.0 V.

Example 2 — Average over a window

* Constant 5V source — average over 2µs to 8µs is still 5V
V1 OUT 0 5.0
R1 OUT 0 1k
.TRAN 1e-8 10e-6

.MEAS TRAN vavg_win AVG V(OUT) FROM=2e-6 TO=8e-6
.END

RMS — Root Mean Square

Purpose: Compute the RMS value of a signal using trapezoidal integration:

$$\text{RMS} = \sqrt{\frac{1}{t_{\text{end}} - t_{\text{start}}} \int_{t_{\text{start}}}^{t_{\text{end}}} V(t)^2 , dt}$$

Example — RMS of a sine wave

For a sine wave with amplitude $A$, the RMS value is $A / \sqrt{2}$:

* 5V amplitude sine at 1MHz — RMS should be ~3.536V
V1 OUT 0 SIN(0 5 1MEG)
R1 OUT 0 1k
.TRAN 1e-9 10e-6

* Skip the first/last partial cycle for a clean measurement
.MEAS TRAN vrms RMS V(OUT) FROM=1e-6 TO=9e-6
.END

Expected result: ~3.536 V ($5 / \sqrt{2} \approx 3.536$).

PP — Peak-to-Peak

Purpose: Compute MAX − MIN in a single measurement. Useful for measuring the full swing of a signal.

* 5V square wave — PP should be 5V
V1 OUT 0 PULSE(0 5 0 1n 1n 5e-6 10e-6)
R1 OUT 0 1k
.TRAN 1e-8 30e-6

.MEAS TRAN vpp PP V(OUT)
.END

Expected result: 5.0 V (max = 5 V, min = 0 V).

INTEG — Integration

Purpose: Compute the trapezoidal integral of a signal over time:

$$\text{INTEG} = \int_{t_{\text{start}}}^{t_{\text{end}}} V(t) , dt$$

The result has units of (signal unit × time unit). For example, integrating a voltage in volts over seconds gives volt-seconds.

Example 1 — Integral of a constant voltage

* 5V for 10µs → integral = 5V × 10µs = 50µV·s
V1 OUT 0 5.0
R1 OUT 0 1k
.TRAN 1e-8 10e-6

.MEAS TRAN vt_integral INTEG V(OUT) FROM=0 TO=10e-6
.END

Expected result: 50 × 10⁻⁶ V·s.

Example 2 — Integral over a sub-window

* Only integrate from 2µs to 8µs → 5V × 6µs = 30µV·s
.MEAS TRAN vt_win INTEG V(OUT) FROM=2e-6 TO=8e-6

DERIV — Derivative at a Point

Purpose: Compute the instantaneous derivative (slope) of a signal at a specific point, using central-difference interpolation.

Syntax — two forms:

* At a specific point
.MEAS <analysis> <name> DERIV <signal> AT=<time>

* At the point where a condition is met
.MEAS <analysis> <name> DERIV <signal> WHEN <condition_signal>=<value> [RISE|FALL|CROSS=<n>|LAST] [TD=<t>]

Example 1 — Slope of a linear ramp

A PWL source ramps from 0 V to 10 V over 10 µs. The slope is constant at $10 / 10 \times 10^{-6} = 10^{6}$ V/s:

* Linear ramp: 0V at t=0, 10V at t=10µs → slope = 1MV/s
V1 OUT 0 PWL(0 0 10e-6 10)
R1 OUT 0 1k
.TRAN 1e-8 10e-6

.MEAS TRAN slope DERIV V(OUT) AT=5e-6
.END

Expected result: 1 × 10⁶ V/s.

Example 2 — Derivative at a threshold crossing (DERIV with WHEN)

Compute the slope of V(OUT) at the moment it crosses 5 V:

* RC charge — derivative when V(OUT) reaches 5V
V1 IN 0 10.0
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

.MEAS TRAN slope_at_5v DERIV V(OUT) WHEN V(OUT)=5
.END

Expected result: ~500 V/s (at $t = \tau \ln 2$, the slope is $\frac{10}{\tau} \cdot e^{-\ln 2} = \frac{10}{0.01} \cdot 0.5 = 500$).

PARAM — Computed Expression

Purpose: Evaluate an arbitrary arithmetic expression that references the results of previously defined measurements. This lets you compute derived quantities like ratios, differences, or more complex formulas.

Syntax:

.MEAS <analysis> <name> PARAM='<expression>'

Important: PARAM measurements must appear after the measurements they reference, because results are computed in order.

Example 1 — Ratio of max to min

* Square wave between 2V and 8V
V1 OUT 0 PULSE(2 8 0 1n 1n 5e-6 10e-6)
R1 OUT 0 1k
.TRAN 1e-8 30e-6

* First, measure max and min
.MEAS TRAN vmax MAX V(OUT)
.MEAS TRAN vmin MIN V(OUT)

* Then compute derived quantities using their names
.MEAS TRAN ratio PARAM='vmax/vmin'
.MEAS TRAN span PARAM='vmax-vmin'
.END

Expected results: ratio = 8/2 = 4.0, span = 8 − 2 = 6.0.

Example 2 — More complex expressions

.MEAS TRAN vmax MAX V(OUT)
.MEAS TRAN vmin MIN V(OUT)

* You can use standard math operators
.MEAS TRAN midpoint PARAM='(vmax+vmin)/2'
.MEAS TRAN pct_swing PARAM='100*(vmax-vmin)/vmax'

FROM/TO Windowing

Any measurement type that scans waveform data (MAX, MIN, AVG, RMS, PP, INTEG, WHEN, FIND/WHEN) supports FROM and TO to restrict the x-axis range:

.MEAS TRAN vmax_win MAX V(OUT) FROM=5u TO=15u
.MEAS TRAN vavg_win AVG V(OUT) FROM=2u TO=8u
.MEAS TRAN t_in_window WHEN V(OUT)=2.5 RISE=1 FROM=0 TO=30e-6

If only FROM is given, measurement runs from FROM to the end of the simulation.
If only TO is given, measurement runs from the start to TO.
If neither is given, the entire simulation range is used.

AC Measurements

For AC analysis, standard V(node) is a complex number, so you need specific export functions:

Export	Description	Example Use
`VM(node)`	Voltage magnitude	Detecting the −3 dB point
`VDB(node)`	Voltage in decibels (20 log₁₀)	Gain in dB
`VP(node)`	Voltage phase (degrees)	Phase margin
`VR(node)`	Real part of complex voltage
`VI(node)`	Imaginary part of complex voltage

Example — Measuring bandwidth from a frequency sweep

.MEAS AC bw_point WHEN VM(out)=0.707
.MEAS AC max_gain MAX VM(out)
.MEAS AC bw_db WHEN VDB(out)=-3

Both the prefix syntax and nested function syntax are supported:

Prefix Syntax	Nested Syntax	Description
`VM(out)`	`mag(V(out))`	Voltage magnitude
`VDB(out)`	`db(V(out))`	Voltage in decibels
`VP(out)`	`phase(V(out))` or `ph(V(out))`	Voltage phase
`VR(out)`	`real(V(out))` or `re(V(out))`	Voltage real part
`VI(out)`	`imag(V(out))` or `im(V(out))`	Voltage imaginary part
`IM(R1)`	`mag(I(R1))`	Current magnitude
`IDB(R1)`	`db(I(R1))`	Current in decibels
`IP(R1)`	`phase(I(R1))`	Current phase

The nested syntax also works in .PRINT, .PLOT, .SAVE, and .WAVE statements.

Accessing Results in C#

Measurement results are automatically collected during simulation and stored in SpiceSharpModel.Measurements, a ConcurrentDictionary<string, List<MeasurementResult>>:

var model = reader.Read(netlist);

// Run all simulations — measurements are computed automatically
foreach (var sim in model.Simulations)
{
    sim.Execute(model.Circuit);
}

// Look up a measurement by its name
if (model.Measurements.TryGetValue("rise_time", out var results))
{
    foreach (var result in results)
    {
        Console.WriteLine($"Rise time = {result.Value} ({result.SimulationName})");
        Console.WriteLine($"Success = {result.Success}");
    }
}

Each MeasurementResult contains:

Property	Type	Description
`Name`	`string`	The measurement name from your `.MEAS` statement
`Value`	`double`	The numeric result (`double.NaN` if the measurement failed)
`Success`	`bool`	`true` if the measurement found a valid result
`MeasurementType`	`string`	One of: `TRIG_TARG`, `WHEN`, `FIND_WHEN`, `FIND_AT`, `MIN`, `MAX`, `AVG`, `RMS`, `PP`, `INTEG`, `DERIV`, `PARAM`
`SimulationName`	`string`	Identifies which simulation produced this result

Interaction with .STEP

When .STEP is used, each sweep point runs as a separate simulation. Each one produces its own measurement, so the result list contains one entry per sweep point:

* Three sweep points → three measurement results
.STEP PARAM V_val LIST 2 5 10
.MEAS TRAN vmax MAX V(out)

This produces 3 entries in model.Measurements["vmax"]. Use the SimulationName property to identify which sweep point produced each result.

Complete Example — Multiple Measurements in One Netlist

This example demonstrates several measurement types together on a single RC circuit:

* RC circuit with pulse input — comprehensive measurements
V1 IN 0 PULSE(0 10 0 1n 1n 25e-3 50e-3)
R1 IN OUT 10k
C1 OUT 0 1u
.IC V(OUT)=0.0
.TRAN 1e-5 50e-3

* Timing: how long from 1V to 9V?
.MEAS TRAN rise_time TRIG V(OUT) VAL=1.0 RISE=1 TARG V(OUT) VAL=9.0 RISE=1

* When does V(OUT) first reach 5V?
.MEAS TRAN t_half WHEN V(OUT)=5.0

* Statistics
.MEAS TRAN vmax MAX V(OUT)
.MEAS TRAN vmin MIN V(OUT)
.MEAS TRAN vavg AVG V(OUT)
.MEAS TRAN vpp PP V(OUT)

* Derived
.MEAS TRAN ratio PARAM='vmax/vmin'
.END

Known Limitations

PARAM measurements must be declared after the measurements they reference (results are computed in declaration order, not via dependency resolution)
When a threshold crossing is not found in the data, the measurement returns Success = false and Value = NaN rather than raising an error

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.MEAS / .MEASURE Statement

General Syntax

Quick Reference — All Measurement Types

Common Qualifiers

Measurement Types In Detail

TRIG/TARG — Timing Measurements

Example 1 — Rise time of an RC circuit

Example 2 — Propagation delay between input and output

Example 3 — Fall time with FALL qualifier

Example 4 — Using CROSS to match any edge direction

Example 5 — Using TD to delay the search start

WHEN — Threshold Crossing Time

Example 1 — When does V(OUT) reach 5 V?

Example 2 — Second rising crossing of a square wave

Example 3 — First falling crossing

Example 4 — Using TD to skip early crossings

Example 5 — Finding the LAST crossing

Example 6 — What happens when the signal never crosses the threshold?

FIND/WHEN — Value at a Threshold Crossing

Example 1 — Output voltage when input crosses 2.5 V

Example 2 — Find current through a resistor when voltage reaches a threshold

Example 3 — Using RISE=2 to pick a specific crossing

FIND/AT — Value at a Specific Point

Example 1 — Voltage at a specific time

Example 2 — Constant voltage check

MAX — Maximum Value

MIN — Minimum Value

AVG — Average Value

Example 1 — DC voltage across a resistor divider

Example 2 — Average over a window

RMS — Root Mean Square

Example — RMS of a sine wave

PP — Peak-to-Peak

INTEG — Integration

Example 1 — Integral of a constant voltage

Example 2 — Integral over a sub-window

DERIV — Derivative at a Point

Example 1 — Slope of a linear ramp

Example 2 — Derivative at a threshold crossing (DERIV with WHEN)

PARAM — Computed Expression

Example 1 — Ratio of max to min

Example 2 — More complex expressions

FROM/TO Windowing

AC Measurements

Example — Measuring bandwidth from a frequency sweep

Accessing Results in C#

Interaction with .STEP

Complete Example — Multiple Measurements in One Netlist

Known Limitations