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Table 1 Signal frequencies leading to the highest scores for electrical variable depending on the chosen terminal configuration

From: Benchmarking electrical methods for rapid estimation of root biomass

Electrical variable Terminal configuration Sensitivity score r 2 max f max (Hz)
Cp 2T 0.71 0.771*** 78
  3T 0.72 0.787*** 116
  4T 0.45 0.560 566
Cs 2T 0.48 0.520** 3
  3T 0.69 0.754*** 6094
  4T 0.28 0.353 20,000
Rp 2T 0.44 0.657*** 78
  3T 0.53 0.797*** 841
  4T 0.00 0.377 9056
Rs 2T 0.45 0.642** 9056
  3T 0.54 0.791*** 4101
  4T 0.00 0.348 20,000
G 2T 0.52 0.585** 78
  3T 0.68 0.751*** 4101
  4T 0.31 0.398 20,000
Z 2T 0.43 0.645*** 78
  3T 0.53 0.795*** 1857
  4T 0.00 0.357 1,3458
X 2T 0.46 0.653** 20,000
  3T 0.55 0.794*** 6094
  4T 0.00 0.330 20,000
θ 2T 0.05 0.331 20,000
  3T 0.10 0.752*** 20,000
  4T 0.26 0.374 0.5
  1. The sensitivity scores, the maximum of the coefficient of determination with root dry mass (r 2 max ) and the maximum determination frequency (f max , in Hz), for parallel capacitance (Cp), serial capacitance (Cs), parallel resistance (Rp), serial resistance (Rs), conductance magnitude (G), impedance magnitude (Z), reactance (X) and phase angle (θ), in 2T, 3T and 4T configurations averaged for the three soil types studied
  2. *** Linear regression is significant at the 0.01 level
  3. ** Linear regression is significant at the 0.05 level