# InstroDMM

## class InstroDMM( name: str | None = None, driver: DMMDriverBase | None = None, publishers: list[Publisher] | None = None, config: DMMConfig | dict | Path | str | None = None, autostart: bool = False, **kwargs, )[source]

Bases: [`Instrument`](https://dev.nominal.io/instro/ref/library/instro.lib.instrument.Instrument.md#instro.lib.instrument.Instrument "instro.lib.instrument.Instrument")

Digital multimeter instrument. Call `set_measurement_function` then `read`, or a single `read_<function>`.

Initialize an InstroDMM.

Provide either `config` or `driver`, not both.

Parameters:
:   - **name**

      Channel-name prefix for published data. Falls back to
      `config.device.name` when `config` is given.
    - **driver**

      Concrete DMM driver; owns its own transport:

      ```
      dmm = InstroDMM(
          "main",
          driver=Agilent34401A("ASRL3::INSTR"),
      )
      ```
    - **publishers**

      Publishers that receive emitted Measurement/Command data.
      Combined with any publishers declared in `config`.
    - **config**

      A `DMMConfig`, a dict, or a path to a JSON config file. Its
      `measurement` block is applied through the public setters on `open()`.
    - **autostart**

      When True, open the connection and start background polling.
      Requires `config` with a `measurement` block, since polling cannot
      start without a measurement function.
    - ****kwargs**

      Default tags applied to every emitted Measurement/Command.
      Pass `dataset_rid="<rid>"` to auto-create a NominalCorePublisher
      (uses the on-disk ‘default’ Nominal credential).

Attributes

| [`background_interval`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.background_interval "instro.dmm.InstroDMM.background_interval") | Seconds between background daemon iterations (0 = no wait). |
| --- | --- |
| [`channel_names`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.channel_names "instro.dmm.InstroDMM.channel_names") | Return an insertion-ordered snapshot of all published channel names. |

Methods

| [`add_background_daemon_function`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.add_background_daemon_function "instro.dmm.InstroDMM.add_background_daemon_function") | Append `method` to the daemon's call list. |
| --- | --- |
| [`add_publisher`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.add_publisher "instro.dmm.InstroDMM.add_publisher") | Register a publisher to receive this instrument's Measurement/Command data. |
| [`close`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.close "instro.dmm.InstroDMM.close") | Close the underlying driver and stop the daemon. |
| [`define_background_daemon`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.define_background_daemon "instro.dmm.InstroDMM.define_background_daemon") | Replace all daemon functions with a single `method` (called with the given args). |
| [`get_channel`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.get_channel "instro.dmm.InstroDMM.get_channel") | Return the most recent `length` samples for `channel_name` from the in-memory buffer. |
| [`get_single_channel_value`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.get_single_channel_value "instro.dmm.InstroDMM.get_single_channel_value") | Return the most recent sample for `channel_name` from the in-memory buffer. |
| [`open`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.open "instro.dmm.InstroDMM.open") | Open the underlying driver and apply any configured measurement state. |
| [`publish`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.publish "instro.dmm.InstroDMM.publish") | Fan `data` out to every configured publisher; `kwargs` pass through. |
| [`read`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read "instro.dmm.InstroDMM.read") | Trigger a measurement under the configured function and return it. |
| [`read_ac_current`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read_ac_current "instro.dmm.InstroDMM.read_ac_current") | Read AC current (amperes), selecting the function first if needed. |
| [`read_ac_voltage`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read_ac_voltage "instro.dmm.InstroDMM.read_ac_voltage") | Read AC voltage (volts), selecting the function first if needed. |
| [`read_dc_current`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read_dc_current "instro.dmm.InstroDMM.read_dc_current") | Read DC current (amperes), selecting the function first if needed. |
| [`read_dc_voltage`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read_dc_voltage "instro.dmm.InstroDMM.read_dc_voltage") | Read DC voltage (volts), selecting the function first if needed. |
| [`read_four_wire_resistance`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read_four_wire_resistance "instro.dmm.InstroDMM.read_four_wire_resistance") | Read 4-wire resistance (ohms), selecting the function first if needed. |
| [`read_resistance`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.read_resistance "instro.dmm.InstroDMM.read_resistance") | Read 2-wire resistance (ohms), selecting the function first if needed. |
| [`set_aperture_nplc`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.set_aperture_nplc "instro.dmm.InstroDMM.set_aperture_nplc") | Set integration time as a number of power-line cycles. |
| [`set_aperture_seconds`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.set_aperture_seconds "instro.dmm.InstroDMM.set_aperture_seconds") | Set integration time (aperture) in seconds. |
| [`set_digits`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.set_digits "instro.dmm.InstroDMM.set_digits") | Set resolution in digits. |
| [`set_measurement_function`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.set_measurement_function "instro.dmm.InstroDMM.set_measurement_function") | Configure the DMM for `function` (DC voltage, resistance, etc.). |
| [`set_range`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.set_range "instro.dmm.InstroDMM.set_range") | Set manual range; `None` selects auto-range. |
| [`start`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.start "instro.dmm.InstroDMM.start") | Start the background daemon thread. |
| [`stop`](https://dev.nominal.io/instro/ref/instruments/instro.dmm.InstroDMM.md#instro.dmm.InstroDMM.stop "instro.dmm.InstroDMM.stop") | Signal the background daemon to stop and join it. |

### property background_interval

Seconds between background daemon iterations (0 = no wait).

### start() → None[source]

Start the background daemon thread.

Raises:
:   [**ValueError**](https://docs.python.org/3/builtins/exceptions.html#ValueError "(in Python v3.15)") – `set_measurement_function` has not been called.

### open() → None[source]

Open the underlying driver and apply any configured measurement state.

### close() → None[source]

Close the underlying driver and stop the daemon.

### set_measurement_function( function: MeasurementFunction, **kwargs, ) → Command[source]

Configure the DMM for `function` (DC voltage, resistance, etc.).

### set_digits(n: int, **kwargs) → Command[source]

Set resolution in digits. Requires set_measurement_function() to have been called.

### set_aperture_seconds( seconds: float, **kwargs, ) → Command[source]

Set integration time (aperture) in seconds. Requires set_measurement_function() first.

### set_aperture_nplc( nplc: float, **kwargs, ) → Command[source]

Set integration time as a number of power-line cycles.

Higher NPLC integrates over more AC noise (better DC/DCI/resistance
accuracy) at the cost of measurement rate. NPLC=100 is the typical
highest-accuracy setting. Requires `set_measurement_function` first.

### set_range( value: float | None, **kwargs, ) → Command[source]

Set manual range; `None` selects auto-range. Requires `set_measurement_function` first.

Publishes `range_mode.cmd` (`"AUTO"`/`"MANUAL"`) on every call and
`range.cmd` (float) only when a manual range is supplied — splitting them
keeps each channel single-typed, which the Nominal streaming backend requires.

### read(**kwargs) → Measurement[source]

Trigger a measurement under the configured function and return it. Requires `set_measurement_function` first.

### read_dc_voltage(**kwargs) → Measurement[source]

Read DC voltage (volts), selecting the function first if needed.

### read_ac_voltage(**kwargs) → Measurement[source]

Read AC voltage (volts), selecting the function first if needed.

### read_dc_current(**kwargs) → Measurement[source]

Read DC current (amperes), selecting the function first if needed.

### read_ac_current(**kwargs) → Measurement[source]

Read AC current (amperes), selecting the function first if needed.

### read_resistance(**kwargs) → Measurement[source]

Read 2-wire resistance (ohms), selecting the function first if needed.

### read_four_wire_resistance( **kwargs, ) → Measurement[source]

Read 4-wire resistance (ohms), selecting the function first if needed.

### add_background_daemon_function( method: Callable, *args, **kwargs, )

Append `method` to the daemon’s call list. Use `define_background_daemon` to replace instead.

### add_publisher( publisher: Publisher, )

Register a publisher to receive this instrument’s Measurement/Command data.

### property channel_names: tuple[str, ...]

Return an insertion-ordered snapshot of all published channel names.

Names are complete after one full daemon iteration: {name}.loop_time publishes
every iteration, so call get_channel(“loop_time”, wait_for_new_samples=True)
then read channel_names to ensure the complete set has arrived.

Raises:
:   [**RuntimeError**](https://docs.python.org/3/builtins/exceptions.html#RuntimeError "(in Python v3.15)") – No background buffer; `start()` was not called.

### define_background_daemon( method: Callable, *args, **kwargs, )

Replace all daemon functions with a single `method` (called with the given args).

### get_channel( channel_name: str, length: int = 1, wait_for_new_samples: bool = False, timeout: float = 10.0, ) → Measurement

Return the most recent `length` samples for `channel_name` from the in-memory buffer.

If the channel does not exist yet, or no sample is available, the code will always block until `timeout` expires.

Parameters:
:   - **channel_name**

      Name of the channel to retrieve.
    - **length**

      Number of trailing samples to return.
    - **wait_for_new_samples**

      Block until at least `length` new values arrive.
    - **timeout**

      Seconds to wait when insufficient data exists or `wait_for_new_samples=True`.

Raises:
:   - [**RuntimeError**](https://docs.python.org/3/builtins/exceptions.html#RuntimeError "(in Python v3.15)") – No background buffer; `start()` was not called.
    - [**ChannelNotFoundError**](https://dev.nominal.io/instro/ref/library/instro.lib.publishers.channel_buffer.ChannelNotFoundError.md#instro.lib.publishers.channel_buffer.ChannelNotFoundError "instro.lib.publishers.channel_buffer.ChannelNotFoundError") – channel had no values and no data appeared before `timeout`.
      `wait_for_new_samples=True` and channel did not appear within `timeout`.
    - [**ChannelValueTimeoutError**](https://dev.nominal.io/instro/ref/library/instro.lib.publishers.channel_buffer.ChannelValueTimeoutError.md#instro.lib.publishers.channel_buffer.ChannelValueTimeoutError "instro.lib.publishers.channel_buffer.ChannelValueTimeoutError") – `wait_for_new_samples=True` and values did not arrive within `timeout`.

### get_single_channel_value( channel_name: str, ) → float | str | None

Return the most recent sample for `channel_name` from the in-memory buffer.

This will not wait, if data is not available then `None` is returned.

Parameters:
:   **channel_name**

    Name of the channel to retrieve.

Raises:
:   [**RuntimeError**](https://docs.python.org/3/builtins/exceptions.html#RuntimeError "(in Python v3.15)") – No background buffer; `start()` was not called.

### publish( data: Measurement | Command, **kwargs, )

Fan `data` out to every configured publisher; `kwargs` pass through.

### stop()

Signal the background daemon to stop and join it. No-op if not running.