The limit of Constant humidity control accuracy, +/- 3% or better?

[jackywschen]

Does anyone know the limit of humidity control accuracy? is it +/- 3%, +/- 1% or even better? Where can find such accurate humidity sensor & controller? Thanks for your comments.

Best regard,

JackywsChen

 

[fredb]

Hello jackywschen

My experience has been that 1 % is easily attainable. There are a number of different ways to generate and control moisture and probably as many different humidity controllers. You could use steam from a small electric boiler, or if you did not want to add heat to your system you could use a mechanical device (sonic) to atomize the water. If you search the web you will probably find a number of different humidity control systems.

Depending on your requirements you might want to be sure that you will have humidity control over your complete temp. range. Also that your air distribution spreads the water vapor over every part of your conditioned space.

One important point. Water vapor behaves like heat in that it always wants to go from a higher to a lower state. You will have difficulty controlling humidity very closely in any conditioned space unless that space is made moisture-tight.

 

[ChasBean1]

Jackiewschen, more important in this application is fine tune temperature control. If you have a constant amount of moisture in the air, a plus or minus one degree temperature swing will vary the room's relative humidity reading in about a 3.4 %RH band.

Ex: You maintain a room 71°F ± 1°F, with a target RH of 50% at 71°. With no change in the air's moisture content, your RH will be 51.6% at 70° and 48.2% at 72°. This temperature control band will vary RH ± 1.7%.

For a 1% humidity control band you would need a very tight room temperature control band and a humidity control scheme that is finely tuned.