The temperature rating of a strain gage type load cell is primarily dependent upon the materials selected for its construction. While the load bearing element is normally good for a relatively wide temperature range, the non-metallic materials in a load cell are quite sensitive to temperature extremes and must be properly selected. This includes strain gage materials, adhesives, and insulations. Most Interface load cell models are rated for an upper operating temperature limit of 200°F. Special models can be made to operate as high as 500°F.
With any set of materials, performance at temperature extremes is nearly always compromised to some extent, relative to performance at nominal temperatures. There are four parameters of interest in examining temperature performance of high temperature cells.
A) Temperature Effect on Zero
The change in zero balance that is due to a change in ambient temperature. It is normally expressed as the slope of a chord spanning the compensated temperature range.
B) Temperature Effect on Output
The change in output that is due to a change in ambient temperature. It is normally expressed as the slope of a chord spanning the compensated temperature range. Note that output is defined as a net value, as the zero load signal is always subtracted from the loaded signal.
The change in load cell signal that occurs with time while under load, and with all environmental conditions and other variables remaining constant. It is normally expressed in units of % of applied load over a specified time interval.
D) Zero Return
The degree to which the initial zero balance is maintained after application and release of a load, while environmental conditions and other variables remain constant.