Datasheet

C
Oscillator
L(d) Rp(d)
C
Oscillator
L(d)
Rs(d)
LDC1000
www.ti.com SNOSCX2 –SEPTEMBER 2013
Generating an alternating magnetic field with just an inductor will consume a large amount of power. This power
consumption can be reduced by adding a parallel capacitor, turning it into a resonator as shown in Figure 9 . In
this manner the power consumption is reduced to the eddy and inductor losses Rs+R(d) only.
Figure 9. LC Tank Connected to Oscillator
The LDC1000 doesn’t measure the series resistance directly; instead it measures the equivalent parallel
resonance impedance Rp (see Figure 10). This representation is equivalent to the one shown in Figure 10 ,
where the parallel resonance impedance Rp(d) is given by: Rp(d)=(1⁄([Rs+R(d)])*([Ls+L(d)])⁄C.
Figure 10. Equivalent Resistance of R
s
in Parallel with LC Tank
Rp = (1/Rs)*(L/C).
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