one year ago
#155 Quote
The sensor mounting screws for the S-1, S-10, S-11, S-16, and S-160 sensors are the 2 pins of a pin type moisture meter.  The S-2 has a plug in port for a cable with ring terminals that are used to connect to two screws which are screwed to the material under test.  The screws create an electric circuit with the material they are screwed into and are used to measure the electrical conductivity of that material.  The wetter the material the greater its conductivity.  So the choice in screws is important to making reliable WME readings.

1 - Always use stainless steel screws and washers.  Its critical they are all made from the same stainless steel alloy, be it 18-8, 304, 316 etc.  Use of "dissimilar metals" will create a battery, i.e. there will be a galvanic potential created which will cause incorrect WME readings.

2 - The screw length is entirely dependent on your application.  The screws will report the wettest material along their length.  #12 x 2" 18-8 Stainless screws and split washers are typically used to mount to 5/8" exterior sheathing.  #10 x 2.5" 18-8 Stainless screws and split washers are typically used to mount to studs and sill plates.

3 - The distance between screws is fixed by the sensor and/or cable to 1.25" but that distance is not critical.

4 - The mounting screws for the S-1, S-10, S-11, S-16, and S-160 go directly through a circuit board.  Circuit boards are tough but bear in mind they are 1/16" thick fiberglass with a very thin layer of copper that will take the load of the screw.  Screws should be "hand tight".  Use of impact or drill drivers for driving screws requires skill to get to "hand tight" with a power tool.  The most common form of sensor damage we see is caused by use of power tools to drive screws through the sensor.

5 - while the S-1, S-10, S-11, S-16, and S-160 are designed for "direct attach" to building materials you have the option of using wires as well.  In other words, use machine screws to connect wires to the sensor and then you can connect the other end of the wires to the material under test.
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