Table 1.

QCM electronic characterization systems qualitative comparison.

Characterization Technique			Advantages	Limitations
Impedance Analysis	Conventional Impedance Analyzers		Highest accuracy. Supports complete sensor characterization and harmonic overtones analysis. Isolated QCM measurements. Adequate for all mediums, provided that appropriate resolution is supported.	Highest setup cost. Large physical size. Some models require time consuming processing/data fitting for accurate parameters extraction.
	Compact Circuitry	VD Based	Significantly cheaper than conventional analyzers with more compact sizing. Provides essential characterization parameters for different applications (e.g., BVD parameters from [4,80]).	Less accurate compared to conventional analyzers. Sensor is not measured in isolation (part of a circuit). Requires time consuming processing algorithms. Some circuits provide limited characterization [38].
		Compact Analyzers	Maintains most conventional impedance analyzers advantages. Rapid and high-resolution measurements capability [72]. Low cost and high integration capability (handheld size).	Less accurate compared to conventional impedance analyzers.
Oscillator Circuits	QCM Oscillators		Highly integrated low cost circuitry. Good accuracy. Direct frequency measurement. Dissipation monitoring capability for some designs.	Sensor response is influenced by circuit components. Inadequate for overtones study. Requires high components stability. $f_{osc}\ne MSRF$ without $C_o^{*}$ compensation in-liquid.
	PLL Based	0-Phase Tracking	Maintains QCM oscillators advantages. Locks in to MSRF. Supports simultaneous interrogation by different overtones for extended results. Provides dissipation monitoring capability through signals indicating $R_m$ variations.	Requires $C_o^{*}$ compensation for MSRF tracking. Circuit components influence may affect the tracking accuracy.
		$G_{max}$ Tracking		Requires high-resolution VCO for flat conductance peaks. Circuit components influence may affect the tracking accuracy.
Exponential Decay (QCM-D)	Conventional		Accurately measures series and parallel resonance. Simultaneous $f$ and $D$ tracking capability and overtones excitation.	Fairly expensive due to its high-quality components. Mainly suitable for lab-based applications (i.e., low portability).
	Contactless		Maintains most conventional QCM-D advantages. Extends the applications spectrum to closed volumes (i.e., no QCM wiring). Electrodeless setup increases the measuring sensitivity.	Contactless setup in [114] is limited for lightly-loaded applications. The wireless interrogation distance is still fairly low for various applications.
Phase-Mass Characterization			Achieves higher sensitivity and resolution compared to conventional circuitry. Supports high-frequency crystals characterization with minimized signals noise and interference. Highly integrated setup, supporting sensing arrays.	Current setup provides partial sensor characterization (e.g., limited dissipation monitoring). Limiting the applications spectrum.