Copy/Paste error iqrf.sensor.STD_SENSOR_TYPE_MAINS_FREQUENCY
https://gitlab.iqrfsdk.org/open-source/iqrf-repository/drivers/blob/master/5E_IqrfStandardSensor.js#L243
https://gitlab.iqrfsdk.org/open-source/iqrf-repository/drivers/blob/master/5E_IqrfStandardSensor.js#L250