I have seen many humidity sensors past few days, for air and soil owever I want to measure humidity (or moisture) of bricks or concrete - automatically, every minute or so Does anyone have a suggestion about what sensor to use? I assume it must be dielectric (hence te title), cause a hole (in bricks) causes measuring difficulties Thanks! Camiel
CamielWijffels: I have seen many humidity sensors past few days, for air and soil owever I want to measure humidity (or moisture) of bricks or concrete - automatically, every minute or so Does anyone have a suggestion about what sensor to use? I assume it must be dielectric (hence te title), cause a hole (in bricks) causes measuring difficulties Thanks! Camiel
The relative moisture in concrete can be determined by the resistivity of the concrete. You will need to calibrate your measurements with a proper device.
At one time in the past I researched that to determine the ESD conductivity of the concrete floor of my plant. Neither cheap nor easy. Basically takes two identically sized metal plates set on the smooth concrete a specific distance apart. The resistance is measured. Takes a rather high voltage.
Probably not a good project for an Arduino.
The moisture content of concrete floors is of great interest to engineers, contractors, and owners, especially for floors that will be covered by relatively impermeable coverings (such as vinyl flooring).
The OP may learn something pertinent to his/her problem by studying how the MC of concrete floors is determined, such as described in this document:
- Polyethylene sheet
- test strip
- moisture (electrical resistance or impedance) meter
- nuclear density & radio freq
- anhydrous calcium chloride
- relative humidity probe
Note that "dielectric" testing is not mentioned.
Also, the linked document describes the limitations of moisture meters: they're ok for comparative measurements but do not provide a quantitative measurement of concrete moisture content.
But, depending on the OP's (unstated) reason for needing moisture content, comparative measurements via moisture meter may be sufficient. Or not.
I already have the LaserLiner MoistureFinder (something like this product: https://www.umarex-laserliner.de/en/product-oversight/100-moisturefinder-compact.html). It is a manual device with a 9V battery, with two rubber pads on the back, which allows me to measure the moisture of bricks and concrete, sold for only 30 euros or so.
By accident (!) I drilled a hole in my brick wall this morning, and it seems that the bricks are dry on the surface (it hasnt been raining for a few days) but they are thoroughly moist! This means 1. I can use some pin-system, which measures the moisture inside the bricks, by means of a small drilled hole - however this wont be very accurate, the bricks are very moist inside! 2. The need to measure every few minutes or hours dissapears, because the moisture inside the bricks wont vaporate within a few days - or even weeks - so measuring once a day will be enough by far, and this can quit easily be done manually
So thanks for the fast and accurate answers