# Revision history [back]

Or is the best way to define each chemical sensor separately?

Well, what are you actually measuring with these sensors? I believe that should be what determines the naming of the message. The fact that a specific message on a specific topic then encodes "ppm CO2 in a certain location" could come from the (standardised) topic name and information in the header (similar to sensor_msgs/Image: if you subscribe to image_raw it's an unprocessed frame, if it's on a left topic (in a stereo setup) it's from the left camera, we don't give those different msg types).

If this would be similar to the Range message however, you'd use an enum for each measured quantity.

From your description it sounds like this message would encode a concentration. Perhaps that would be a good name? Or more specific: what type of concentration?

Or is the best way to define each chemical sensor separately?

Well, what are you actually measuring with these sensors? I believe that should be what determines the naming of the message. The fact that a specific message on a specific topic then encodes "ppm CO2 in a certain location" could come from the (standardised) topic name and information in the header (similar to sensor_msgs/Image: if you subscribe to image_raw it's an unprocessed frame, if it's on a left topic (in a stereo setup) it's from the left camera, we don't give those different msg types).

If this would be similar to the Range message however, you'd use an enum for each measured quantity.

From your description it sounds like this message would encode a concentration. Perhaps that would be a good name? Or more specific: what type of concentration?

Edit: gas concentration? For liquids it would be molarity apparently.