you know an accurate humidistat can cost as much as $700 if its digital and dewpoint makes things feel a lot more humid.you have relative humidity and absolute humidity .relative humidity is the ratio of partial pressure of water vapor in the mixture to saturated vapor pressure at a given temperature which is water content and temperature.absolute humidity is the total amount of water vapor in a given volume of air it does not take temperature into consideration.then we have specific humidity which is what most guys here are measuring .that is ratio of water mass to the airs total mass of dry air.its a mixing ratio .A hygrometer is a good way to measure humidity content.what you really want to measure is relative humidity because our pets also require heat.
- Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer and the difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. Relative humidity can also be determined by locating the intersection of the wet and dry-bulb temperatures on a psychrometric chart. as i am a licensed hvac and refrigeration technition i know about this. A hygrometer is a device used for measuring the humidity of air. Relative humidity (abbreviated RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at the same temperature. This is why my frogs can be left at a different humidity level and be comfortable .And griff if you are reading this i am a mechanical engineer , you can have 80 percent humidity in the winter .you have the metal paper type of hygrometer whose accuracy is very limited with variations of 10 percent or more and actual hair tension hygrometer like the one i use is much more accurate.a psychromter is the actual best thing to use along with a psychometric chart.So we want to measure relative humidity in the tank .I used a psychrometer and set a mark on my hair tension hygrometer and thus i get what i consider to be the proper humidity for my frogs.