Thoughts from construction and structural engineering background:
1: Usually the placing of concrete is a rough procedure, and nothing is 
immune from impact damage!
2: It's not said what the concrete purpose or configuration is, but many 
times the concrete area gets congested with reinforcing bar, pipes, and 
conduit. The structural engineer should be consulted, he is the 
coordinating body for items in the concrete. The structural integrity 
will dictate where items may not be, to insure strength where needed.
3: It is preferred only to embed one metal in the concrete to minimize 
corrosion (think a battery with 2 dissimilar metals).
4: I like the idea of using a conduit, and install the sensor later, 
then the sensor and cable material is not that critical. Think a 
thermometer well use in piping installations. These work very well. A 
pipe coupling is welded to the pipe, the well (a blind end short pipe) 
is threaded on and then the thermometer is inserted. The conduit or well 
should be sealed tight for concrete casting, end preferably on a wall or 
column vertical surface, protected from damage and water infiltration.
5: Probably no necessary, but if a greater heat transfer to the sensor 
is desired, the conduit could be filled partially with an oil or other 
substance.

Volker Soffel wrote:
> I'm looking at a cheap way of embedding temperature sensors (thermistor)
> into a concrete slab. The sensors will be placed before the concrete is poured.
> I'm wondering how to best protect the sensor and the leads going to the sensor
> from chemical reactions with the concrete & moisture?
> I would welcome any suggestions & first hand experiences.
> What type of encasing would you suggest for the sensor. Sensor leads, 
> what type of cable,
> cable mantel material? Should the cable be run in a conduit/ can it 
> be buried directly in the concrete....
> 
> best regards
> Volker
> MicroController Pros Corporation
> microcontrollershop.com
> The World's Largest Embedded Tool Selection
> +1-408-776-7992 Phone
> +1-215-243-6071 Fax  
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