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On the Temperature Compensation of Magnetic Variometer by means of Magnetic Shunt Alloy
The temperature compensation of the magnetic variometer has been investigated from various point of views, which is usually of the order of 10γ - 15γ/℃.
The writer succeeded in keeping the temperature coefficient as small as 0.0γ/℃ by means of a magnetic shunt alloy of Fe-Ni-Cr system specially made in the laboratory (Metal Matter) of the Tohoku University. This alloy has many following characters.
1. The magnetic Curie point A３ is 100°- 150°C.
2. The temperature coefficient of permeability is very large.
3. This is no Curie point except A３.
4. The characters are not changed by cold work, cooling, heating etc.
5. There is a linear relation between permeability and temperature in interval of 10 - 600℃.
The simple bar magnet is considered to be best fit for the magnetic variometer. In this case, the condition to make the temperature-coefficient to zero is as follows:
Q１：Temperature coefficient of magnetic moment.
Q２：Temperature coefficient of quartz fibers rigidity.
N ：Demagnetization factor.
V０：Volume of the magnet.
V ：Volume of the shunt alloy.
α ：Temperature coefficient of permeability of shunt alloy.
Recently he has also succeeded in making a new portable variometer by using the shunt alloy mentioned above. It can be used in field where the change of temperature is 10°- 20℃, and its stability is very high (accuracy is about 0.5γ).
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