Humidifiers for respiratory gases

A method of determining the state of a humidification chamber in a respiratory gas humidifier, the method comprising:

• emitting a first electromagnetic radiation signal having a first intensity from a transmitter, and receiving the first electromagnetic radiation signal at a receiver having a first gain setting, such that the receiver provides a first output signal to a controller, the first output signal indicative of the amount of electromagnetic radiation received at the receiver;
• emitting a second electromagnetic radiation signal having a second intensity from a transmitter, and receiving the second electromagnetic radiation signal at a receiver having a second gain setting, such that the receiver provides a second output signal to a controller, the second output signal indicative of the amount of electromagnetic radiation received at the receiver;
• and
• comparing the first output signal with a first threshold value, and determining that the humidification chamber is in either i) a first state, or ii) one of two further states;
• and
• when it is determined that the humidification chamber is in ii) one of two further states, comparing the second output signal with a second threshold value to determine whether the humidification chamber is in a second state or a third state,
• wherein the first intensity is different from the second intensity, and/or the first gain setting is different from the second gain setting.

A humidifier comprising:

• a humidification chamber;
• and
• a sensor comprising:
• a transmitter for emitting an electromagnetic radiation signal;
• a receiver for receiving the electromagnetic radiation signal and providing an output signal indicative of a received amount of electromagnetic radiation at the receiver, the transmitter and the receiver positioned at opposing walls of the humidification chamber;
• and
• a controller configured to:
• vary an intensity of the electromagnetic radiation signal emitted by the transmitter and/or a gain setting of the receiver;
• receive the output signal from the receiver;
• and
• compare a value of the output signal with one or more threshold values, the controller having:
• a first sensor configuration in which the controller causes the transmitter to emit a first electromagnetic radiation signal having a first intensity and the receiver to have a first gain setting, the output signal provided to the controller by the receiver being a first output signal indicative of the amount of the electromagnetic radiation received at the receiver;
• and
• a second sensor configuration in which the controller causes the transmitter to emit a second electromagnetic radiation signal having a second intensity and the receiver to have a second gain setting, the output signal provided to the controller by the receiver when in the second sensor configuration being a second output signal indicative of the amount of electromagnetic radiation received at the receiver, wherein the first intensity is different from the second intensity, and/or the first gain setting is different from the second gain setting, and the controller compares the first output signal with a first threshold value, and determines that the humidification chamber is in either i) a first state, or ii) a one of two further states, and when it is determined that the humidification chamber is in ii) one of two further states, the controller compares the second output signal with a second threshold value to determine whether the humidification chamber is in a second state or a third state.