pymeasure Tools

These 4 tools are only available when pymeasure is installed:

pip install mcpyvisa[pymeasure]

They complement the raw SCPI tools documented in Universal Tools. Use the pymeasure tools when a driver exists for your instrument — they provide property validation, type conversion, and high-level methods that encode multi-step SCPI sequences. Fall back to instrument_query and instrument_write for instruments without a pymeasure driver, or for operations not covered by the driver.

Currently supported instruments: HP 33120A, HP 34401A, HP 3478A, HP 8657B, Agilent 4284A, Keithley 2000, Keithley 2400, Keithley 6517B.

Instruments are addressed by VISA resource string ("GPIB0::24::INSTR") or by a configured alias ("smu").

---

instrument_inspect

Discover a pymeasure driver’s validated properties and methods for an instrument. This is the starting point — run it first to see what operations are available before calling instrument_get, instrument_set, or instrument_call.

If no pymeasure driver is found for the instrument, returns a message suggesting raw SCPI access instead.

Parameters

Name	Type	Required	Description
instrument	string	Yes	VISA resource string or configured alias

Example

result = await client.call_tool("instrument_inspect", {
    "instrument": "smu"
})

Returns

For an instrument with a matching driver (e.g., a Keithley 2400):

pymeasure driver: keithley-2400 (Keithley2400)
Instrument: smu (GPIB0::24::INSTR)

Use instrument_get/instrument_set/instrument_call for validated access.

# Keithley2400

Represents the Keithley 2400 SourceMeter and provides a high-level
interface for interacting with the instrument.

## Measurements (read-only -- triggers a measurement)
  - `current`  (SCPI: :MEAS:CURR?) -- Reads the current in Amps
  - `resistance`  (SCPI: :MEAS:RES?) -- Reads the resistance in Ohms
  - `voltage`  (SCPI: :MEAS:VOLT?) -- Reads the voltage in Volts

## Controls (read + write -- get/set with validation)
  - `compliance_current` (SCPI: :SENS:CURR:PROT? / :SENS:CURR:PROT %g) -- Current compliance value in Amps
    Valid: [0, 1.05]
    Validator: truncated_range
  - `compliance_voltage` (SCPI: :SENS:VOLT:PROT? / :SENS:VOLT:PROT %g) -- Voltage compliance value in Volts
    Valid: [0, 210]
    Validator: truncated_range
  - `source_current` (SCPI: :SOUR:CURR? / :SOUR:CURR:LEV %g) -- Source current in Amps
    Valid: [-1.05, 1.05]
    Validator: truncated_range
  - `source_mode` (SCPI: :SOUR:FUNC:MODE? / :SOUR:FUNC:MODE %s) -- Source mode
    Valid: ['current', 'voltage']
    Validator: strict_discrete_set
  - `source_voltage` (SCPI: :SOUR:VOLT? / :SOUR:VOLT:LEV %g) -- Source voltage in Volts
    Valid: [-210, 210]
    Validator: truncated_range

## Methods (high-level operations)
  - `apply_current(current_range, compliance_voltage)` -- Configure and apply a source current
  - `apply_voltage(voltage_range, compliance_current)` -- Configure and apply a source voltage
  - `enable_source()` -- Enable the source output
  - `disable_source()` -- Disable the source output
  - `shutdown()` -- Safely shut down the instrument, disabling the source output

When no driver is found:

No pymeasure driver available for instrument GPIB0::7::INSTR.

Use instrument_query() and instrument_write() for raw SCPI access.

Supported instruments with pymeasure drivers:
  - hp-33120a: pymeasure.instruments.hp.HP33120A
  - hp-34401a: pymeasure.instruments.hp.HP34401A
  - hp-3478a: pymeasure.instruments.hp.HP3478A
  - hp-8657b: pymeasure.instruments.hp.HP8657B
  - agilent-4284a: pymeasure.instruments.agilent.Agilent4284A
  - keithley-2000: pymeasure.instruments.keithley.Keithley2000
  - keithley-2400: pymeasure.instruments.keithley.Keithley2400
  - keithley-6517b: pymeasure.instruments.keithley.Keithley6517B

Note

The inspect result is generated from the pymeasure driver class at runtime. It reflects the actual properties and methods available — not a static list.

---

instrument_get

Read a property value from an instrument using its pymeasure driver. For measurement properties, this triggers an actual measurement on the instrument. For control properties, it queries the current setting. pymeasure handles response parsing, type conversion, and unit handling internally.

Run instrument_inspect first to see available properties.

Parameters

Name	Type	Required	Description
instrument	string	Yes	VISA resource string or configured alias
property	string	Yes	Name of the property to read (from instrument_inspect output)

Example

# Read a measurement property (triggers a real voltage measurement)
result = await client.call_tool("instrument_get", {
    "instrument": "smu",
    "property": "voltage"
})

# Read a control property (queries the current source mode setting)
result = await client.call_tool("instrument_get", {
    "instrument": "smu",
    "property": "source_mode"
})

Returns

For a measurement property:

voltage = 4.99823

For a control property:

source_mode = 'voltage'

Tip

For bulk reads, call instrument_get multiple times. Each measurement property read triggers a fresh measurement on the instrument.

---

instrument_set

Set a control property on an instrument. The pymeasure driver validates the value before sending the SCPI command — out-of-range or invalid values are rejected without reaching the instrument, protecting expensive equipment from bad parameters.

Run instrument_inspect first to see available properties and their valid ranges.

Parameters

Name	Type	Required	Description
instrument	string	Yes	VISA resource string or configured alias
property	string	Yes	Name of the control property to set
value	string	Yes	Value to set (automatically converted to the correct type)

Example

# Set a numeric control property
result = await client.call_tool("instrument_set", {
    "instrument": "smu",
    "property": "source_voltage",
    "value": "5.0"
})

# Set a discrete control property
result = await client.call_tool("instrument_set", {
    "instrument": "smu",
    "property": "source_mode",
    "value": "voltage"
})

Returns

Successful set:

Set source_voltage = 5.0

Validation failure (value out of range):

Validation error for 'source_voltage' = '999': 999 is not in range [-210, 210]

Validation failure (invalid discrete value):

Validation error for 'source_mode' = 'plasma': 'plasma' is not in the discrete set ['current', 'voltage']

Attempting to set a read-only measurement property:

Property 'voltage' is read-only (measurement)

Caution

You can only set control properties (read/write). Attempting to set a measurement property (read-only) or call a non-existent property returns an error.

---

instrument_call

Call a high-level method on an instrument. Methods often encode multi-step SCPI sequences — for example, apply_voltage on a Keithley 2400 might configure source mode, voltage level, and compliance current in a single call.

Run instrument_inspect first to see available methods and their parameters.

Parameters

Name	Type	Required	Description
instrument	string	Yes	VISA resource string or configured alias
method	string	Yes	Name of the method to call (from instrument_inspect output)
kwargs_json	string	No	JSON object of keyword arguments (default: "{}")

Example

# Call a method with keyword arguments
result = await client.call_tool("instrument_call", {
    "instrument": "smu",
    "method": "apply_voltage",
    "kwargs_json": '{"voltage_range": 5.0, "compliance_current": 0.1}'
})

# Call a method with no arguments
result = await client.call_tool("instrument_call", {
    "instrument": "smu",
    "method": "shutdown"
})

# Call enable_source before taking measurements
result = await client.call_tool("instrument_call", {
    "instrument": "smu",
    "method": "enable_source"
})

Returns

For a void method:

Called apply_voltage(voltage_range=5.0, compliance_current=0.1)

For a method with no arguments:

Called shutdown()

For a method that returns a value:

measure_current() returned: 0.04723

Note

The kwargs_json parameter accepts a JSON string, not a Python dict. For example: '{"voltage": 5.0}' not {"voltage": 5.0}. The tool parses the JSON and passes the resulting keyword arguments to the pymeasure method.