esphome-docs/components/sensor/ct_clamp.rst

CT Clamp Current Sensor
=======================

.. seo::
    :description: Instructions for setting up ct clamp sensors.
    :image: ct_clamp.jpg

The Current Transformer Clamp (``ct_clamp``) sensor allows you to hook up a CT Clamp to an analog
voltage sensor (like the :doc:`ADC sensor <adc>`) and convert the readings to measured single phase AC current.

First, you need to set up a voltage sensor source (:doc:`ADC sensor <adc>`, but for example also
:doc:`ADS1115 <ads1115>`) and pass it to the CT clamp sensor with the ``sensor`` option.

Please also see `this guide <https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/introduction>`__
as an introduction to the working principle of CT clamp sensors and how to hook them up to your device.

.. figure:: images/ct_clamp-ui.png
    :align: center
    :width: 80.0%

.. code-block:: yaml

    # Example configuration entry
    sensor:
      - platform: ct_clamp
        sensor: adc_sensor
        name: "Measured Current"
        update_interval: 60s

      # Example source sensor
      - platform: adc
        pin: A0
        id: adc_sensor

Configuration variables:
------------------------

- **sensor** (**Required**, :ref:`config-id`): The source sensor to measure voltage values from.
- **sample_duration** (*Optional*, :ref:`config-time`): The time duration to sample the current clamp
  with. Higher values can increase accuracy. Defaults to ``200ms`` which would be 10 whole cycles on a 50Hz system.
- **update_interval** (*Optional*, :ref:`config-time`): The interval
  to check the sensor. Defaults to ``60s``. The **update_interval** for ``ct_clamp`` has to be greater than **sample_duration**.
- All other options from :ref:`Sensor <config-sensor>`.

Calibration
-----------

This sensor needs calibration to show correct values, for this you can use the
:ref:`calibrate_linear <sensor-filter-calibrate_linear>` sensor filter. First, hook up a known
current load like a lamp that uses a known amount of current.

Then switch it on and see what value the CT clamp sensor reports. For example in the configuration below
a 4.0 A device is showing a value of 0.1333 in the logs. Now go into your configuration file

.. code-block:: yaml

    # Example configuration entry
    sensor:
      - platform: ct_clamp
        sensor: adc_sensor
        name: "Measured Current"
        update_interval: 60s
        filters:
          - calibrate_linear:
              # Measured value of 0 maps to 0A
              - 0 -> 0
              # Known load: 4.0A
              # Value shown in logs: 0.1333A
              - 0.1333 -> 4.0

Recompile and upload, now your CT clamp sensor is calibrated!

See Also
--------

- `EMonLib <https://github.com/openenergymonitor/EmonLib>`__
- `CT Clamp Guide <https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/introduction>`__
- :doc:`adc`
- :doc:`ads1115`
- :apiref:`sensor/ct_clamp_sensor.h`
- :ghedit:`Edit`