There is one IEC guideline, number is IEC 599,
Statement of guideline is that "If the ratio of carbon dioxide and Carbon monoxide in Dissolve gas analysis test result is more than 11, it is predict that the condition of paper insulation inside the transformer is poor."
For healthy condition this ratio will be between 4 to 11.
Thermistors are ideal when measuring a single point temperature that is within 50°C of ambient.
If the temperatures are excessively high or low, a thermistor will not work.
Most thermistors work best in the range between -55°C and +114°C.
Sensitivity of thermistor is high.
Span value of thermistor is low.
The V-curves of a synchronous motor show relationship between Armature current (Ia) and Excitation current (If).
The Inverted V-curves of a synchronous motor show relationship between power factor (pf) and field excitation (If).