Theory:
Certain measurements made at an ECIMOS station vary with ambient air temperature. Therefore, the limits of an acceptable measurement should change as temperature changes. ECIMOS stores the equation of the variance, which represents the optimal running condition at a given ambient temperature. Then allowable tolerances above and below the optimal measurement are assigned.

Determining the Variance:
To determine how much, if any, a given measurement varies, ECI provides an office utility called “Ambient Temperature Analysis”. This analysis is run for a group of like models, or for a single model. The tool will analyze stored data, based on user criteria such as date range and line number, and return an equation of the best-fit line. Correlation coefficient and quantity of data points will be displayed to the user, who can use this information to determine if this measurement should be temperature compensated. If it should, the slope and y-intercept are stored along with a user defined name and description of this analysis. Therefore, the system will eventually contain stored equations for each model group and measurement.

Adding to the Test Procedure:
Once the equation of the variance is in the system, the test procedure must be directed to use the equation. Typically, the test to check the measurement will already be in the test procedure, with the low and high parameters set. By right clicking on the low parameter and the high parameter, you can assign the properly named equation to each parameter independently. The numbers in the high and low parameter fields will determine the allowable tolerance. The difference of the parameters will be halved, and this number will be subtracted from the optimum measurement to derive the low parameter, and added to the optimum measurement to derive the high parameter.

At Test Time:
While the test is running, the system will continuously read the ambient temperature and determine the optimum measurement. The compensated low and high parameters will be calculated, and the actual reading will be checked.