Usually, waffle thermostat frames are made of metal, but there are manufacturers that make waffle thermostat frames using plastic molds. This is a fatal error because the plastic has a large deflection/flexibility that increases the temperature fluctuation, not to mention over time, the plastic gets brittle and breaks easily. On the other hand, you may also need to visit http://thermostatonline.com/ when you need to buy thermostats online.
Another type of thermostat commonly used is a type of coiled thermostat (it contains mercury). But considering this type of thermostat is the application for refrigerator/refrigerator, it usually also has a large temperature fluctuation, which can reach 3-4 degrees Celsius.
The most modern thermostats are electronic and digital. However, since the majority of these types of thermostats are applications for refrigeration, the temperature fluctuations are also large. Exceptions to a specially-set thermostat with the temperature approaching hatching temperature and adjustable hysteresis up to +/- 0.1-degree Celsius. This type of thermostat is rarely applied to small semi-automatic hatching capacities because it is so expensive that it is more suitable for full automatic hatching machines / large capacity, as it will be worth the price. However, be careful not to use hysteresis that is too small because it can cause damage problems due to the breaker components will work much harder.