esphome-docs/components/sensor/ct_clamp.rst
2019-06-01 16:25:14 +02:00

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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:
------------------------
- **name** (**Required**, string): The name of the sensor.
- **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``.
- **id** (*Optional*, :ref:`config-id`): Manually specify the ID used for code generation.
- 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.h`
- :ghedit:`Edit`