Circuit arrangement for compensating for the influence of temperature on coil quality
First Claim
1. A circuit arrangement comprising:
- a first coil having N1 turns, which includes a first inductor and a first variable ohmic resistor; and
a second coil magnetically coupled with the first coil and having N2 turns, which includes a second inductor and a second variable ohmic resistor, wherein the number of turns N2 of the second coil deviates from the number of turns N1 of the first coil at the most by 10%; and
an NTC thermistor, which is connected in series with the second coil so that the second coil and the NTC thermistor are connected in parallel with the first coil, the NTC thermistor being selected so that, in conjunction with the two variable ohmic resistors, said circuit arrangement has a specified total ohmic resistance value Rg which is substantially independent of temperature.
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Accused Products
Abstract
To compensate for the temperature dependence of a resonant circuit, it is known to use an a.c. current source, with which the resonant circuit is excited in dependence upon the ohmic resistance of the coil conductor material. The task of compensating for temperature may to be solved without a costly closed-loop control process and with few losses. A magnetically coupled second coil is connected in parallel with the first coil to be compensated, and an NTC thermistor is connected in series with one of the two coils so that the series connection is connected in parallel with the other of the two coils. The NTC thermistor is selected so that, in conjunction with the two variable sized ohmic resistors of the two coils, the circuit arrangement has a specified total ohmic resistance, which is substantially independent of temperature.
17 Citations
9 Claims
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1. A circuit arrangement comprising:
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a first coil having N1 turns, which includes a first inductor and a first variable ohmic resistor; and a second coil magnetically coupled with the first coil and having N2 turns, which includes a second inductor and a second variable ohmic resistor, wherein the number of turns N2 of the second coil deviates from the number of turns N1 of the first coil at the most by 10%; and an NTC thermistor, which is connected in series with the second coil so that the second coil and the NTC thermistor are connected in parallel with the first coil, the NTC thermistor being selected so that, in conjunction with the two variable ohmic resistors, said circuit arrangement has a specified total ohmic resistance value Rg which is substantially independent of temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification