![](https://static.wixstatic.com/media/356d0cee84164a4cb8304d44630a7ea6.png/v1/fill/w_1920,h_1080,al_c,q_95,usm_0.66_1.00_0.01,enc_auto/356d0cee84164a4cb8304d44630a7ea6.png)
HD37… CO2, CO2 and Temperature Transmitters
![HD37… CO2, CO2 and Temperature Transmitters](https://static.wixstatic.com/media/94e8db_3a155f79599d45c0ad33ca1fa34a4644~mv2.jpeg/v1/fill/w_704,h_561,al_c,q_85,usm_0.66_1.00_0.01,enc_auto/Image-empty-state.jpeg)
The HD37BT… and HD37VBT… series transmitters are used mainly in air quality control by measuring CO2(Carbon Dioxide) in the ventilation systems.
This allows you to vary the number of air change per hour according to ASHRAE and IMC norms.
The purpose is twofold: to have a good air quality in the presence of people and to save energy, increasing or decreasing parts of air per hour, depending on the air quality set. The use is for environments where there is overcrowding of people, discontinuous crowding, cafeterias, auditoriums, schools, hospitals, greenhouses, livestock breeding, etc.
The HD377BT… and HD37V7BT… models measure, in addition to CO2, also the temperature.
The analog outputs, current 4…20mA or voltage 0…10Vdc, should be specified when ordering. All transmitters have an alarm digital output suitable to control, for example, an external relay coil.