dave-in-nj:
need more data.unfortunately, the content of honey is not pure so the resistance per mm will not be constant.
the two nail probe used for soil moisture, or wood moisture is a possibility, but the base resistance would need to be known.a humidity sensor used to detect the moisture in air could be used if you have a closed environment for your honey. say inside of the hive
do you need an instant (more or less) you would need to use a refractometer. I have not seen one for use with an arduino.
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Thanks for the advice guys! 
Yes, I can use a honey moisture refractometer, there is a digital one, but I don't know how to utilize it in Arduino. Plus it is very expensive.
I need the arduino to process the data of the moisture content into our system. Has anyone know how a digital refrac can somehow be used in Arduino?
Your replies would be a great help Thank you!