Stability: Bondable Resistance Temperature Sensors

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Stability
In common with most other organic resin systems, the matrix of TG sensors will slowly sublimate and lose strength when aged at elevated temperatures. When properly installed, life will be essentially infinite below +250° F (+120° C), and will be approximately 10 000 hours at +400° F (+205° C). At +500° F (+260° C), life can be estimated at 1000 hours in the presence of air, and will be considerably extended if an inert atmosphere is used.

The sensing grids are quite stable under the aging conditions described above. If exposed to temperatures above +500° F (+260° C), however, a slight shift in resistivity will occur, together with a small change in temperature coefficient. For example, if the WTG-Series sensor is exposed to a temperature of +600° F (+315° C) for one hour, the +75.0° F (+23.9° C) resistance will shift from 50 ohms to approximately 50.6 ohms. On a normalized basis, the resistance increase from +75.0° to +450° F (+23.9° to +232° C) will become 140% instead of the previous 143%. Operation at temperatures below +550° F (+290° C) will thereafter be stable and repeatable.

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