# VirtualELoad

## class VirtualELoad( source_voltage: float = 12.0, source_resistance: float = 0.5, )[source]

Bases: [`ELoadDriverBase`](https://dev.nominal.io/instro/ref/instruments/instro.eload.ELoadDriverBase.md#instro.eload.ELoadDriverBase "instro.eload.eload.ELoadDriverBase")

Single-channel E-Load simulated in-process: no transport, server, or hardware.

The load sinks from a simulated source: a fixed voltage behind an internal resistance. With the
input off the terminals read the open-circuit voltage at 0 A; with it on, the readings are the
operating point the active mode and level set on that source, plus noise (0.5%). As on the
`BK85XXB`, `short_output` also switches the input: a short pulls the terminals to 0 V at the
source’s short-circuit current, and ending it turns the input off. Range and slew-rate settings
are accepted and have no effect on readings, so any `InstroELoad` call works.

Levels the source cannot reach are not errors: CC and CR stop at the short-circuit current, and
CP stops at the source’s maximum power (half its open-circuit voltage), where a real load would
lose regulation. There are no ratings, protections, or time dynamics.

Create a virtual E-Load.

Parameters:
:   - **source_voltage** ([*float*](https://docs.python.org/3/builtins/functions.html#float "(in Python v3.15)"))

      Open-circuit voltage of the simulated source, in volts. Must not
      be negative.
    - **source_resistance** ([*float*](https://docs.python.org/3/builtins/functions.html#float "(in Python v3.15)"))

      Internal resistance of the simulated source, in ohms. Must be
      positive; it sets how far the voltage sags as the load draws current.

Both stay settable as attributes, e.g. to sag the source mid-run, and are validated on
every set.

Raises:
:   [**ValueError**](https://docs.python.org/3/builtins/exceptions.html#ValueError "(in Python v3.15)") – If `source_voltage` is negative or `source_resistance` is not positive.

Example:

```
from instro.eload import InstroELoad, LoadMode
from instro.eload.drivers import VirtualELoad

eload = InstroELoad(name="eload", driver=VirtualELoad(source_voltage=12.0, source_resistance=0.5))
with eload:
    eload.set_mode(LoadMode.CC)
    eload.set_level(2.0)
    eload.output_enable(True)
    print(eload.get_current().latest)  # about 2.0
    print(eload.get_voltage().latest)  # about 11.0
```

Attributes

| [`source_resistance`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.source_resistance "instro.eload.drivers.virtual.VirtualELoad.source_resistance") | Internal resistance of the simulated source, in ohms. |
| --- | --- |
| [`source_voltage`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.source_voltage "instro.eload.drivers.virtual.VirtualELoad.source_voltage") | Open-circuit voltage of the simulated source, in volts. |

Methods

| [`close`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.close "instro.eload.drivers.virtual.VirtualELoad.close") | Nothing to disconnect. |
| --- | --- |
| [`get_current`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.get_current "instro.eload.drivers.virtual.VirtualELoad.get_current") | Measure the current the load is sinking on `channel` (amperes). |
| [`get_voltage`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.get_voltage "instro.eload.drivers.virtual.VirtualELoad.get_voltage") | Measure the voltage at `channel`'s terminals (volts). |
| [`open`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.open "instro.eload.drivers.virtual.VirtualELoad.open") | Nothing to connect to. |
| [`output_enable`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.output_enable "instro.eload.drivers.virtual.VirtualELoad.output_enable") | Turn the input on or off; a short set by [`short_output`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.short_output "instro.eload.drivers.virtual.VirtualELoad.short_output") stays set. |
| [`set_level`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.set_level "instro.eload.drivers.virtual.VirtualELoad.set_level") | Set `mode`'s level; each mode keeps its own. |
| [`set_mode`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.set_mode "instro.eload.drivers.virtual.VirtualELoad.set_mode") | Set the operating mode on `channel`: CC, CV, CP, or CR. |
| [`set_range`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.set_range "instro.eload.drivers.virtual.VirtualELoad.set_range") | Accepted; no effect on readings. |
| [`set_slewrate`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.set_slewrate "instro.eload.drivers.virtual.VirtualELoad.set_slewrate") | Accepted; no effect on readings, which settle instantly. |
| [`short_output`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.short_output "instro.eload.drivers.virtual.VirtualELoad.short_output") | Start or end a short; like the `BK85XXB`, this also turns the input on or off. |

### property source_voltage: float

Open-circuit voltage of the simulated source, in volts.

### property source_resistance: float

Internal resistance of the simulated source, in ohms.

### open() → None[source]

Nothing to connect to.

### close() → None[source]

Nothing to disconnect.

### short_output(enable: bool, channel: int) → None[source]

Start or end a short; like the `BK85XXB`, this also turns the input on or off.

The short stays set until `short_output(False)`: turning the input off and on again with
`output_enable` leaves it shorted, as `INPut` alone leaves `INPut:SHORt` on the BK85XXB.

### set_mode( mode: LoadMode, channel: int, ) → None[source]

Set the operating mode on `channel`: CC, CV, CP, or CR.

Not every model supports every mode; drivers should raise
`NotImplementedError` for unsupported combinations.

### set_level( mode: LoadMode, value: float, channel: int, curr_limit: float | None, ) → None[source]

Set `mode`’s level; each mode keeps its own. `curr_limit` caps the current in CV mode.

### set_range( mode: LoadMode, value: float, channel: int, ) → None[source]

Accepted; no effect on readings.

### set_slewrate( direction: SlewRateDirection, rate: float, channel: int, ) → None[source]

Accepted; no effect on readings, which settle instantly.

### output_enable(enable: bool, channel: int) → None[source]

Turn the input on or off; a short set by [`short_output`](https://dev.nominal.io/instro/ref/instruments/instro.eload.drivers.virtual.VirtualELoad.md#instro.eload.drivers.virtual.VirtualELoad.short_output "instro.eload.drivers.virtual.VirtualELoad.short_output") stays set.

### get_current(channel: int) → float[source]

Measure the current the load is sinking on `channel` (amperes).

### get_voltage(channel: int) → float[source]

Measure the voltage at `channel`’s terminals (volts).