How to adjust the bimetallic thermometer indicator deviation?

Bimetallic thermometer as a kind of measuring instrument, in our life more and more used in the field. After using for a long time, we may find its temperature values indicate deviation, so how to adjust the deviation? In fact to find the problem, we have to in two ways. 1. Bimetallic thermometer is no problem. Specifically, we have just bought two the same specifications of the bimetallic thermometer, sometimes, we are curious or for other reasons, we will put them in a container (at the same time Such as bucket) And then to see whether it measured temperature is the same. Normally, we think they should be the same. Actual situation is not because the container is not normally a constant temperature, so when we put the two thermometer at the same time in measurement, the temperature in different parts of the would is actually not the same. 2. Bimetallic thermometer itself has a problem. When we take two new bimetallic thermometer, directly at room temperature, observe it, if shows large difference of reading, is one of the only changed. Normally, we will send the bad repair, rather than adjust themselves. Because after repair to check job need professional personnel through professional equipment complete.