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SEARC OSOTF Design and Operations Manual

2,496 bytes added, 15:21, 11 October 2011
Regular maintenance of the system should be performed to ensure that all connections in the box are secure, and should be checked every time wiring is modified inside the box. In addition, at times of high humidity, desiccant should be utilized to limit the humidity inside the measurement enclosure.
 
== Panel Thermal Measurement ==
All panels were monitored for back sheet temperature at a minimum of one point. If channels were available, two points at the top and bottom of the panel were measured, as there have been recorded differences in temperature over the length of a panel. In order to translate from back sheet temperature to cell temperature, a correlation is available from [Sandia Laboratories http://photovoltaics.sandia.gov/docs/PDF/King%20SAND.pdf] (eq.12).
 
===Thermocouples===
The temperature of the back sheet of each panel was measured utilizing site-fabricated thermocouples. The thermocouples were created by purchasing outdoor compatible duplex insulated SLE (Special limits of error) thermocouple wire. The wires were run from the data acquisition box to each panel, and cut to length. It is critical to label both ends of the wire with a durable label to ensure proper hook-up. Both ends were then stripped and a portable [thermocouple welder http://dcccorporation.thomasnet.com/item/thermocouple-welders/hotspot-i-ii-thermocouple-welders/item-1112?&plpver=10&origin=compare&filter=0&CTypeID=2] was used to create a solid junction at the panel side. For future designs, however, it would be recommended to utilize [shielded thermocouple wires http://www.omega.com/ppt/pptsc.asp?ref=TT-J-TWSH&Nav=temh06] to protect against electrical interference over the long spans of wire required.
 
===Thermocouple mounting===
The thermocouples were mounted to the rear face of each panel using alumized tape. In addition, a thermally conductive paste was used to ensure full thermal contact of the thermocouple with the back face of the panel. The typical installation procedure was to cut a piece of tape approximately 1.5"X1.5", place a pea-sized amount of thermal paste in the center of the tape, and seat the thermocouple junction in this paste. The entire unit was then affixed to the rear of the panel. In terms of placement, the thermocouple was placed at the absolute center of amorphous panels, or in the case of crystalline panels at the center of an individual cell which was closest to the center of the panel, in order to ensure a proper reading of cell temperature.
 
===Multiplexer attachment===
The thermocouples were wired into AM 25T multiplexers. These multiplexers are solid state devices and include integrated cold-point calibration and should be used for all thermocouple measurements. For a wiring schematic of the AM 25T see the wiring diagrams section.
== Panel Electrical Measurement ==
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