GB2336685A

GB2336685A - Capacitance measuring system

Info

Publication number: GB2336685A
Application number: GB9808258A
Authority: GB
Inventors: Christopher Barnes
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-04-21
Filing date: 1998-04-21
Publication date: 1999-10-27
Anticipated expiration: 2018-04-21
Also published as: GB9808258D0; GB2336685B

Abstract

A method or means, suitable for measuring electrical capacitance, includes monitoring one or more changes in the output signal form a quartz crystal or piezoelectric oscillator 3. The changes in the oscillator output signal may relate to a change in the capacitance of a capacitive item Cx connected to the oscillator and/or changes in the interconnection of the capacitive item Cx to the said oscillator 3. The monitored signal changes are then processed to derive an output signal with a value which directly or indirectly relates to the capacitance of the capacitive item Cx. Temperature 25 and humidity 26 compensation techniques may be employed to improve the accuracy of the measuring system. The capacitance measuring system may be used in an arrangement to monitor or test the dielectric state or electric field changes occurring within various fluids.

Description

2336685 A Method and Device for the Measurement of Fixed or Time Varying

Capacitance There are several traditional methods for the measurement of electrical capacitance including, for example, a.c. impedance bridges, substitution methods and direct impedance methods with low frequency oscillator drive sources. None of these methods are, however, particularly suited to the determination of capacitance in the picofarad or sub-picofarad ranges, nor to the detection of small changes thereof, such as may be required in the determination of various properties of a sample via dielectric affects. Manufactured capacitors are not available with sufficiently accurate tolerances to make substitution wholly viable and direct impedance/attenuation methods are very prone to drift as oscillator amplitude and/or frequency varies. Also these latter methods are usually limited to low measurement frequencies of, typically, 1, 5 or 10 KHz. On the other hand, small value capacitors are generally employed in circuits operating at frequencies of several or many megahertz, where such peculiarities as component resonances can be manifest which are not discernible by low frequency methods.

It is established that the working output frequency of certain types of crystal oscillator can be altered, usually lowered, by the inclusion of trimmer capacitors or padders into their circuitry. This phenomenon has been used to correct and/or adjust the output frequency of crystal oscillators, crystal controlled clocks, radio transmitters, frequency synthesisers etc., with the padder capacitor being manually adjusted by means of a non-metallic trimming tool to bring the oscillator frequency to a nominal pre-requisite value. It is believed that the treatment of the present Inventor in redirecting this phenomenon as a methodology for capacitance measurement, is unique. It has further been enabled by private research of the present Inventor into the precise functionality of the output frequency response of certain types of crystal oscillator to the inclusion of a range of different values of shunt capacitance into their crystal circuits.

Page 1 It should be noted that series capacitances and shunt and series inductances with natural self or additional induced lump capacitance across their whole or part, also cause predictable affects in this output function. The present invention, therefore, advantageously provides a much more accurate method based around parallel mode quartz crystal oscillators or oscillators employing other piezoelectric devices, eg ceramics, for the measurement of static or time varying electrical capacitance, either directly from connection with the terminals of an electronic capacitor, or indirectly as a manifestation of the dielectric properties of a material sample in any phase or state, or of any component thereof based on monitoring the output frequency functionality of said oscillator in response to addition of said capacitance substantially in series or in parallel (shunt) with terminals of said crystal said oscillator or, if not wholly so, then at least such that some component of the aforesaid capacitance appears as being electronically traceable or analysable as being either in series or in parallel with the piezo-electric device or crystal dielectric or electrostatic capacitance. The methodology according to the present invention functions because a quartz crystal has a series-parallel equivalent circuit with the mechanical resonance of the vibrating shear mode plate being represented by the series arm of this circuit, and the dielectric or electrostatic capacitance of the quartz or other piezoelectric being represented by the parallel arm which also contains in parallel with itself the crystal package or housing capacitance, the electrical capacitance of the connecting leads and any external shunt capacitance in the circuit. In certain crystal oscillator circuits designed specifically to excite the parallel resonant frequency, the shunt capacitance, ie of connection leads etc., is highly significant. Any shunt capacitance causes a lowering of the output frequency towards the nominal series resonant point. Although mathematically speaking there ought to be a non-linear relationship between the degree of downward frequency shift at the oscillator output and the value of added parallel capacitance, the present Inventor has found that at least over small ranges in the region 0-30 picofarads linearity is, in fact, quite reasonable. Linearity of this function has been found by the present Inventor to be best for Pierce type oscillators and Meacharn Bridge type Page 2 oscillators where the linear regression factor R was in excess of 0.99 in the 0-30 picofarad capacitance range. With a Bruckenstein oscillator, this was not so good and R was only about 0.8, but this was improved by restricting the range of shunt capacitance to 0-7.5 picofarad. For a truly series mode crystal oscillator, there was no further shift of frequency when a shunt capacitor was applied across the crystal terminals as expected. Indeed, oscillation became quite unstable which was not a feature with parallel mode systems.

Further, within the scope of the present invention, the Inventor has also explored the relationship between shunt capacitance across the crystal or such other piezoelectrical device, terminals and oscillator output amplitude, which has the strongest functionality for oscillators such as Pierce types employing specifically variable transconductance devices which tend to exhibit a large self-reactance swing as a function of supply voltage. A linear relationship between added parallel capacitance and change in output amplitude has been established by the present Inventor over limited ranges of capacitance as for the frequency response methodology above.

The present Inventor has further made the observation that both the abovementioned frequency and amplitude responses and their attendant mathematical relationships, may be used to measure the value of additional capacitance shunted directly across the terminals of the quartz crystal in certain types of parallel mode crystal oscillators, either as a direct result of the electrical connection of an electronic capacitor, or when shunt or series capacitance is introduced to the crystal more indirectly, say when it is connected to electrodes or an inductor disposed of on the outside of an electrically insulating measuring cell, into which may be introduced material samples whose molecular, dielectric or bulk properties may manifest a capacitance (or change therein) at the crystal, because of perturbation of the electric field through the measuring cell, giving a resultant change in capacitance across the said electrodes or a change in lump capacitance associated with the said inductor and appearing across all or any of

Page 3 its turns. Thus, the measurement of such manifest capacitance or change therein may be a valuable pointer to an absolute property of the sample or one of its components or changes therein, and indeed the said manifest capacitance (or its change) may be directly correlatable with (linearly or otherwise) or proportional to (directly or otherwise) the said sample property thus in such a case, the said manifest capacitance thereby effectively being employed as a means of measurement of the said sample property.

With some liquid materials, it is better to measure their capacitance by way of changes in the induced lump capacitance of the inductor based measuring cell and by using single frequencies in the region of 19 MHz.

According to the present invention, there is provided a method for measuring static or time varying electrical capacitance, either directly as is required for an unknown electronic capacitor, or indirectly as manifest by dielectric, molecular, bulk or other properties of a sample of any material or component thereof comprising the steps of connecting the capacitor or sample substantially in series or in parallel with the electrical terminals of an oscillating quartz crystal or other oscillating piezo-electric device, or by allowing the sample to produce manifest capacitance or capacitance change by means of the perturbation of electric fields in an electrically insulating measuring cell with external electrodes or inductor with natural and additional lump capacitance, substantially connected in parallel or in series with the quartz crystal or piezo-electric device terminals, but allowing any stray capacitances to couple to earth and comprising the further steps of monitoring the output frequency and/or amplitude of the oscillations of the said oscillator with and without the said electronic capacitor or sample in situ or monitoring the same during any said cycle of change with the said sample in situ, and storing or recording the said frequency or frequency changes and/or voltages, or voltage changes and applying mathematical algorithms thereto, in the form of hardware or software, such that the numeric or voltage output from the said algorithms is/has either the numeric value of the said electrical capacitor in

Page 4 picofards or is/has a value either directly equal to or proportional thereto or correlateable therefrom the said molecular, dielectric, bulk or other property of the said sample or component thereof, giving rise to the said indirect manifestation of electrical capacitance or said change thereof.

Further, advantageously, according to the present invention, measurements can be made sequentially over a range of frequencies, either by manually changing the crystal, or device, switching a bank of crystals or piezoelectric devices or by switching the capacitor or capacitance due to sample under test between a bank of such oscillators. This is desirable because in some cases, resonant behaviour or selective dielectric absorption means than an electronic capacitor or physical sample will behave differently at one particular frequency or within a particular frequency group than another. In the case of a physical sample, this can mean that some properties are best correlated at one frequency region than another.

Likewise, according to the present invention, there is provided apparatus for the measurement of electrical capacitance or changes thereof for use either to directly measure the electrical capacitance of an electronic capacitor, or as a means of obtaining measurement therefrom said capacitance or said changes thereof a molecular, dielectric, bulk or other property or change thereof in a material sample or component thereof, by means of correlation or proportionality with manifest capacitance therefrom, as a result of either direct electrical connection thereto said apparatus, or by means of perturbations of electrical fields in measurement cells of said apparatus, with said apparatus comprising means for providing electrical connection of said electrical capacitor, said sample or said measuring cell substantially in series or parallel with the electrical connections of an oscillating quartz crystal or other oscillating peizoelectric device, either directly or by means of switch, and providing appropriate means to cause said quartz crystal or said other piezo-electric device to oscillate close to its natural parallel mode resonant frequency, and providing means to monitor the output frequency of said oscillator and/or output voltage amplitude of said oscillator and

Page 5 providing means to mathematically correlate by hardware or software said frequencies or/and voltages or changes therein with said capacitance or said manifest capacitance or said sample properties or changes therein, finally providing appropriate means of numeric output or display device.

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawing in which:

Figure 1 shows the method of connecting and switching the electronic capacitor or sample (substantially also an additional capacitor Cx) in this example, substantially in parallel with the quartz crystal of a parallel mode crystal oscillator, and also shown path of stray capacitance to earth and also showing that frequency output has some functionality of Cx.

Figure 2 shows similar method as in Figure 1 but using oscillator based around a device with high mutual transconductance such that large reactive swing enables output amplitude to map or mirror frequency response and that thus output amplitude response has same or similar functionality with Cx.

Figure 3 shows alternative method for providing output amplitude or voltage proportional to Cx.

Figure 4 shows typical output frequency response as a function of additional substantially parallel capacitance Cx, from invention configured as in Figure 1.

Figure 5 shows typical voltage plot from invention configured according to Figure 2.

Figure 6 shows method of inserting sample to give a manifestation of capacitance Cx across electrodes of measuring cell by means of perturbation of electrical field within cell, cell has substantially circumferential electrodes.

Page 6 Figure 7 shows method similar to that shown in Figure 6 according to present invention but with substantially parallel electrodes.

Figure 8 shows block diagram of apparatus according to present invention with either analog or digital display; also included are optional corrections for ambient temperature and humidity.

Figure 9 shows block diagram of apparatus according to present invention operated in a differential mode, in order to minimise electronic system drifts.

Figure 10 shows how present invention may be used to follow a time varying physical system, which gives rise to a time independent capacitance change, eg glycerol, a viscous liquid running down the inside of a sealed glass container of approximately 12mrn internal diameter until it reaches positional equilibrium.

Figure 11 shows an example of how the present invention can be used to monitor the aggregation of solid particles within a liquid.

Referring then to the drawings: Figure 1 shows the general principle of capacitance measurement according to the present invention where 1 is the unknown capacitor or sample capacitance Cx, 2 is any stray capacitance to earth, 3 is a quartz crystal, 4 is a parallel mode crystal oscillator designed to nominally excite the crystal at or close to parallel resonance. The frequency output of 4 falls when additional parallel capacitance is added across 3 by closing switch SW. The degree of frequency fall in f (Cx) is a measure of Cx.

Figure 2 shows an extension of the principle explained by Figure 1 and above in Figure 2, items 1-3 are as previously described. However, in this case the oscillator, 5, employs a device with a very high mutual conductance and capable of a large reactive swing for small changes in supply voltage. Such devices as the HEF 4049BP high performance CMOS family are ideal in this role when Page 7 i configured as Pierce type quartz crystal oscillators. Due to its own self- reactance the oscillator acts rather like it has a built in reactance modulator such that its output amplitude is proportional or almost proportional to changes in working frequency when SW is closed. Thus, the output amplitude also has a strong functionality of Cx, see also Figure 5.

Figure 3 shows yet another aspect of the present invention. Here, the configuration is rather similar to that in Figure 1, except in that there are additional electronic components present in the output circuit. A half-wave rectifier assembly 9-11 is connected to the oscillator output by means of a series filter component which may either be a crystal filter 8 or simple single crystal 7 working at a frequency very close to 3 and having an optional phasing control 6. The purpose of the assembly 6- 11 is to provide a voltage Vaf (Cx) by means of a slope detection technique. Thus the voltage V across 11 is then a direct function of Cx. Figures 6 and 7 show ways of using the present invention to measure the electrical capacitance manifest by the insertion of a sample into measuring cell 12.

In these cases, the sample is interrogated without direct electrical contact due to the way in which the sample perturbs the electrical field(s) within 12. In more detail, Cx and 3-5 operate as described earlier. In Figure 6, Cx is manifest and developed between nominally circumferential electrodes 13 and 14 wrapped around the outer circumference of, or disposed within wall of, insulating container 12, but alternatively 13 and 14 may be supported in mid air, being held at a minimum number of points. 15 is an optional earthed guard ring to carry away stray capacitance to earth and 16 is any material sample of appropriate size which may even be liquid or gas if held within or passing through its own separate electrically insulating container. Dielectric induction perturbs the electric field within 12 and between 13, 14 and (15) from the empty condition to a different set of conditions when the sample is introduced. Alternatively, the sample may already be present and undergoing time dependent change in its

Page 8 dielectric or molecular properties. The modus operandi of the set up shown in Figure 7 is very similar to that of Figure 6, except that substantially parallel vertically mounted electrodes generate the field within 12. The arrangement of Figure 6 is more suitable for the detection of gravity dependent change such as might be encountered from moving viscous liquids or in fluids within a sedimenting component(s).

Figure 8 shows a block diagram of an apparatus according to the present invention where 1 is the unknown capacitor or sample with unknown capacitance, 3 is the quartz crystal, 4 is a parallel mode crystal oscillator with either analog or digital signal processing employed at its output. When analog processing is being employed, this is normally (although not limited exclusively by the scope of the claims herein) along the lines of 19-21, where 19 is a frequency to voltage converter, 20 is an analog processing circuit generating an appropriate algorithm and 1 is an analog display device, which may be replaced by or used in conjunction with a chart recorder or similar device if a time dependent sample property is giving rise to manifest capacitance change. Optionally temperature and humidity correction may also be employed by feeding outputs of sensors 25 and 26 into 20. Alternatively in the case of digital signal processing, the signal from 4 is routed via 22-24 where 22 is a frequency counter, 23 is a digital algorithm which may be held in hardware or entered through software and where the whole digital operation may be CPU or SIMM card controlled and where 24 is a digital display. In the digital case, the optional environmental correction is applied from sensors via Analog to Digital converters 27 and 28. If the sample parameter is time varying, a data logging system may be employed.

Figure 9 shows an alternative block diagram according to the present invention, the advantage of which is differential operation which tends to cancel electronic and environmental drift. The circuit can be arranged to operate with a pair of oscillators 4, configured according to either Figures 1 or 3 or with a pair of oscillators 5 operating as their individual counterparts in Figure 2 with either Page 9 their frequency or voltage outputs being connected to an appropriate mixer or difference circuit 20. An analog or digital processing circuit 30 provides an appropriate algorithm for measuring the sample parameter of interest. Again optional and additional environmental correction is provided by 25 and 26.

Figures 10 and 11 are provided as examples of how various types of sample property may be studied via the present technique because of the time dependent capacitance change which they manifest.

It should be remembered that use of the present invention is not simply limited to these systems described above, nor are these meant to present a limitation on the scope of the present claims herein below. The aspects of the invention described above have dealt with quantitative evaluation, but it should be remembered that qualitative change is easier to detect and manifest qualitative capacitive change may occur if apparatus according to the invention is operating close to detection limits, such as for instance might be the case in various forms of medical specimen testing.

In cases of use of antibody, antigen type reaction or enzyme amplified interactions, all that is often necessary is a detector of quantitative change and as such, the present invention can also have application. In these types of reaction, chemical or biochemical reagent(s) is/are often added to blood, urine or other body fluids or vice versa, such reagent tubes can easily be inserted into the tube 12 of the present apparatus.

In many electronic systems, frequency and phase measurement are synonymous, similar, or at least performed for similar reasons or to yield similar information. Thus with the present invention it is also possible to measure the phase of the emergent oscillator signal(s) and extract the capacitance or manifest capacitance information referred to in the aforegoing methods and apparatus. Phase measurement lends itself best (although not exclusively) to the differential Page 10 arrangement of the present invention (Figure 9) and in such a case, the mixer or difference circuit 20 is replaced with a phase sensitive detector. Similarly, some crystal oscillator systems lend themselves to the possibility of closed or open loop control of frequency, phase and amplitude, either separately or together, and oscillators employing such control systems also have uses within the scope of the present invention, whereby arrangements can be configured according to the present in which measurement of the control voltage required in a frequency and/or phase loop controlled system linked to at least one oscillator, having the aforesaid fixed or time varying capacitance or manifest capacitance substantially in parallel with its crystal would yield by mathematical proportion or algorithm a measure of this aforesaid capacitance, or a measure of the aforesaid property(ies) which may give rise to manifest capacitance via electric field perturbation from a sample. In these cases, the aforesaid control voltage is in itself a proportionate measure of the aforesaid amplitude, frequency or phase or changes therein, according to the present invention.

The present invention, method and apparatus may also be used to follow the growth of biological cells, the movement of cells or cellular components, including for instance protein and DNA fragments as these phenomena all give rise to small time dependent capacitance changes. Other uses, including monitoring component contents of liquids, emulsions, colloids, solutions and suspensions, rates of dissolution, rates of. charge evolution etc.

Page 11

Claims

Claims

A method for measuring static or time varying electrical capacitance, either directly as is required for an unknown electronic capacitor, or indirectly, as when the said electrical capacitance is manifest by the molecular, dielectric o other bulk properties of a sample of any material in any state or phase or by any component thereof, comprising the steps of connecting the said capacitor or sample substantially in parallel with the electric terminals of an oscillating quartz crystal or piezo-electric device or by allowing the sample to produce manifest capacitance or a manifest capacitance change by means of its,perturbation of electric fields set up in an electrically insulating measuring cell, having electrodes connected substantially in parallel with the aforesaid,quartz crystal connections, but allowdstray capacitance to couple to earth, method further comprising the steps oF monitoring the output frequency and/or amplitude and/or phase of the oscillations of the said oscillator with and without the said sample in situ and storing or recording the said frequency changes and/or voltages and/or phase changes and further applying algorithms thereto in the form of hardware or from software, such that the numeric or voltage output form said algorithms has either numeric value of said capacitor in picofarads or is/has a value directly equal to proportional to, or correlatable from one of the said properties of the sample or component thereof or said change therein said property having given rise to initial manifestation of capacitance or change thereof.

A method exactly as in Claim 1, except where the capacitance and/or electrodes of the measuring cell appear substantially in series with the quartz crystal or piezo-electric device.

A method as in either of Claims 1 or 2 wherein the said substantially in series or in parallel capacitance arise from or appears as natural or additional lump capacitance of an inductor connected substantially in series or in parallel with said crystal or piezo-electric device and wherein said lump capacitance or changes therein may appear across all or any of turns of said inductor.

4. A method as in any of Claims 1-3, but where multiple quartz crystals or piezo-electric devices or their oscillators are individually selected by manual or automatic sequential switching or scanning.

ti- 5. A method as in Claim 4 wherein the act of frequency selection results in better correlation or proportionality being attained between the manifest capacitance and the measurement parameter.

6. A method as in any of Claims 1-5 wherein the output amplitude of the oscillations has functionality with the additional or additional manifest capacitance Cx because of the use of an oscillator device with a high mutual conductance and large self-reactive swing.

A method as in any of Claims 1-6 wherein additional series filter components are employed at the oscillator output in conjunction with a rectifer assembly to provide a voltage output by slope detection.

8. A method as in any of Claims 1 -6 wherein measurement of the manifest capacitance or sample property is made without direct electrical contact between the sample and the crystal connecting wires because the manifest capacitance is via perturbation of electric fields.

9. A method as in Claim 8 wherein circumferential electrodes are employed.

lo. A method as in Claim 8 wherein substantially parallel electrodes are employed.

A method as in Claim 8 wherein an inductor is employed to convey manifest capacitance to the crystal/piezo- electric oscillating circuit by means of its own lump capacitance.

12. A method as in any of Claims 8-11 wherein the sample is inserted into an insulating container.

13. A method as in any of Claims g- 12 wherein the electrodes are disposed of on or in the wall of the container or in air with minimal support, 14. A method as in any of Claims 8-13 wherein the sample is a liquid or gas contained within or moving through its own glass or polymeric container.

15. A method as in any of Claims 8-12 wherein the property of the sample correlatable with or proportional to the manifest capacitance is the viscosity of a liquid.

R.

16. A method as in any of Claims 8-14 wherein the. process of aggregation of solid particles in a liquid detected because this being the process giving rise to manifest time varying capacitance, said liquid may be an emulsion, colloid or suspension.

17. A method as in any of Claims 1-14 for measuring or monitoring specific component contents of a liquid, said liquid may be an emulsion, colloid, suspension or solution.

18. A method as in any of Claims 15 - 17 wherein quantitative or qualitative change in the manifest capacitance being monitored is brought about by external influence, such as for instance the bringing together of the two or more components required for a chemical or biochemical reaction, eg antibody antigen, enzyme substrate and enzyme amplified reactions.

ig. A method as in Claim 18 wherein pathological disease states are detectable, as a result of manifest capacitance change.

20. A method as in any of Claims 1-19 wherein the frequency or phase or amplitude is obtained indirectly as a function of a loop control voltage.

21. Method as in any of Claims 1-20 wherein said capacitance or manifest capacitance appears if not directly in shunt with crystal terminals, at least in a manner that some component of it is electronically traceable or analysable as appearing in parallel with dielectric or electrostatic capacitance of said crystal.

22. Apparatus for the measurement of static or time varying electrical capacitance, either directly from an electronic capacitor, or indirectly from capacitance manifest by a molecular, dielectric or bulk property of a sample thus to yield numeric output either of capacitor value in picofarads, or numeric value of sample property, because it is correlatable with or proportional thereto said manifest capacitance comprising means for connecting said capacitor or said manifest capacitance substantially in series or in parallel with the terminals of an oscillating quartz crystal or similar piezo-electric device at or near parallel resonance, with means for stray capacitance to be permitted to leak to earth, said connection being made either directly or by means of a switch and appropriate means being provided to oscillate said crystal or other similar piezo-electric device and appropriate means provided within said apparatus to measure output frequency of said oscillator and/or output voltage amplitude and/or output phase of said oscillator, where said phase or frequency may be obtained by measurement of i - a loop control voltage if said means to provide loop is included and also providing means for said frequency being measured by means of frequency counter or to frequency/voltage convertor and means being provided for digital and/or analog processing of information contained in frequency or voltage function emergent from said oscillator means being provided for application of algorithm thereto and finally having means of providing display device for display of numeric or graphical output therefrom.

23. Apparatus as in Claim 22 wherein a differential circuit or difference method is employed.

24. Apparatus as in Claim 22 or 23 wherein environmental correction is employed.

25. Apparatus as in any of Claims 22-24 wherein said oscillator is arranged to oscillate a series of crystals or similar piezo-electric devices sequentially by manual or automatic switching and where sequential scanning is used advantageously to home in on a frequency region of interest when the sample is dielectrically dispersive.

26. Apparatus as in Claim 25 but wherein actual oscillators are successively scanned or switched rather than just crystals or piezoelectric devices alone.

27. Apparatus as in any of Claims 22-26 wherein said capacitance is manifest from a liquid sample of any component thereof, said liquid being either a solution, suspension, colloid or emulsion.

I.:) Amendments to the claims have been filed as follows A method for measuring static or time varying electrical capacitance either directly as is required to ascertain the static capacitance of an unknown electronic capacitor, or indirectly as when the said static or time varying electrical capacitance is manifest by the molecular, dielectric or other bulk properties of a sample of any material in any state or phase or by any component thereof, comprising a first step of connecting the said capacitor or sample substantially in series with the electrical terminals of an oscillating quartz crystal, or by allowing the sample to produce a manifest capacitance or a manifest capacitance change by means of its perturbation of electric fields set up in an electrically insulating measuring cell, making substantially series connection with the aforesaid quartz crystal connections, but allowing stray capacitance to couple to earth, method further comprising the second step of monitoring the output amplitude of the said oscillator with and without the said sample in situ, and storing or recording the said amplitude voltage changes and further applying algorithms thereto in the form of hardware or from software, such that the numeric or voltage output from said algorithms has either numeric value of said capacitor in picofarads, or is/has a value directly equal to, proportional to or correlatable from one of the said properties of the sample or component thereof, or said change therein, said property having given rise to initial mInifestation of capacitance or change thereof.

2. A method as in Claim 1, but where multiple quartz crystals or oscillators are individually selected by manual or automatic sequential switching or scanning.

3. A method as in Claim 2 wherein the act of frequency selection results in better correlation or proportionality being attained between the manifest capacitance and the measurement parameter.

Page 14 4. A method as in any of Claims 1-3, wherein the output amplitude of the oscillations has functionality with the additional or additional manifest capacitance, because of the use of an oscillator device with a high mutual conductance and large self-reactive swing.

5. A method as in any of Claims 1 -5, wherein measurement of the manifest capacitance or sample property is made without direct electrical contact between the sample and the oscillating piezoelectric device connecting wires, because the manifest capacitance is via perturbation of electric fields.

6. A method as in Claim 5, wherein electrodes are employed.

7. A method as in Claim 5 wherein substantially parallel electrodes are employed.

8. A method as in Claims 6 or 7, wherein an additional electrode assists in coupling of stray capacitance to earth.

9. A method as in any of Claims 6-8, wherein the sample is insulating container.

inserted into an 10. A method as in any of Claims 6-9, wherein the electrodes are disposed of on or in the wall of the container, or in air, with minimal support.

11. A method as in any of Claims 6-10, wherein the sample is a liquid or gas contained within or moving through its own glass or polymeric container.

92. A method as in any of Claims 1 - 11, wherein the property of the sample correlatable with or proportional to the manifest capacitance, is the viscosity of a liquid.

13. A method as in any of Claims 1 - 12 above, used for various forms of medical specimen testing.

M 14. A method as in any of Claims 1-13, wherein quantitative or qualitative change in the manifest capacitance, hence process being monitored is brought about by external influence, such as for instance the bringing together of the two or more components required for a chemical or biochemical reaction, eg antibody antigen, enzyme substrate and enzyme amplified reactions.

15. A method as in Claims 13 or 14, wherein pathological disease states are detectable.

16. A method as in any of Claims 1 - 15, wherein the phase or amplitude is obtained indirectly as a function of a loop control voltage.

17. A method as in any of Claims 1-16, wherein the said substantially in series 1 capacitance arises from or appears as the natural or -additional lump capacitance of an inductor connected substantially in series with the said crystal or piezoelectric device.

w A method as in Claim 17, wherein the said lump capacitance appears across all of the turns of the said indicator.

ig. A method as in Claim 17, wherein the said lump capacitance appears across any of the turns of the said inductor.

20. A method as in any of Claims 1-19, wherein differential techniques are employed.

21. A method as in any of Claims 1-20, wherein the frequency(ies) of oscillator(s) are measured.

22. A method as in any of Claims 1-20, wherein the capacitance or manifest capacitance appears in parallel with the said piezoelectric device instead of in series.

Is 23. A method as in Claim 22, wherein said capacitance or manifest capacitance appears if not directly in shunt with crystal terminals, at least in a manner that some component of it is electronically traceable or analysable in parallel with dielectric or electrostatic capacitance of said crystal.

24. Method as in any of Claims 1-23, wherein phase is measured instead of amplitude or frequency.

25. Apparatus for carrying out any of the methods of Claims- 1-20, ic for the measurement of static or time varying electrical capacitance, either directly from an electronic capacitor, or indirectly from capacitance manifest by said molecular or dielectric sample property, thus to yield numeric output either of capacitor value in picofarads, or numeric value of sample property, because it is correlatable with or proportional thereto said manifest capacitance, comprising means for connecting said capacitor, or said manifest capacitance in series with the terminals of an oscillating quartz crystal, said connection substantially in series although stray capacitance is permitted to leak to earth, said connection being made either directly or by means of a switch and appropriate means being provided to oscillate said crystal, and appropriate means provided within said apparatus to measure output voltage amplitude from oscillator, and means being provided for digital and/or analog processing of information contained in said amplitude voltage function emergent from said oscillator, means being provided for application of algorithm thereto and finally having means of providing display device for display of numeric or graphical output therefrom.

26. Apparatus as in Claim 25, wherein a differential circuit or difference method is employed.

27. Apparatus as in Claims 25 or 26, wherein said environmental correction is employed.

lq 28. Apparatus as in any of Claims 25-27, wherein said oscillator is arranged to oscillate a series of crystals sequentially by manual or automatic switching, and where sequential scanning is used advantageously to home in on a frequency region of interest when the sample is dielectrically dispersive.

29. Apparatus as in Claim 28, wherein said actual oscillators are successively scanned or switched, rather than just their crystals alone.

30. Apparatus as in any of Claims 25-30, wherein said capacitance is manifest from a liquid sample and any component thereof, said liquid being a solution, colloid, suspension or emulsion.

39. Apparatus as in any of Claims 25-30, wherein said capacitance or manifest capacitance appears in parillel or substantially in parallel with said piezoelectric device, instead of in series, ie for carrying out method according to any of Claims 22-24 above.

32. Apparatus as in any of Claims 25-30 above, wherein phase instead of amplitude is measured, ie for carrying out Claims 16 or 24 above.

33. Apparatus as in any of Claims 25-30 above, wherein series capacitance is employed, but wherein frequency instead of or in addition to amplitude is measured, ie for carrying out Claim 21 above.

34. Apparatus as in Claim 31, wherein phase instead of amplitude is measured.

35. Apparatus as in any of Claims 25-30, wherein additional series filter components are employed at the oscillator output to provide an amplitude voltage output.

36. Apparatus as in Claim 35, wherein said voltage output arises from slope detection.

2- o 37. Apparatus as in Claim 31, but with same additional components as apparatus of Claim 35 or 36.

38. Apparatus as in Claim 33, but with same additional components as apparatus in Claims 35 or 36.

f- 1