referring first to fig2 x and γ are position parameters respectively representing the translation and rotation of the weight in relation to its neutral or nominal controlled position , i . e . that position in which the weight is centered with respect to the electrodes and its faces are respectively parallel to said electrodes . the voltages applied to the four electrodes of surface area s and to the weight impart to the latter , when x and y are zero : a force along axis x of ## equ1 ## and a torque having a moment normal to the plane of the figure ## equ2 ## where 2d is the distance between the centers of two electrodes relative to the coordinate axis . this force and torque are directly proportional to the translation and rotational control voltages v x and v . sub . γ . this configuration accordingly makes it possible to achieve linear position control of the weight in relation to the electrodes . as shown in fig3 such control is realized with two capacitive sensors or detectors d 1 and d 2 , used to measure the translation x and the rotation γ of the weight ; the four electrodes are identical and the sensitivities of the detectors are the same . the sum of the outputs of the detectors thus solely reflects translation distance x , whereas the difference between the detector outputs reflects rotation angle γ . based on the position data so obtained , two servo loops of the &# 34 ; proportional plus integral plus derivative &# 34 ; ( pid ) type determine the appropriate control voltages v x and v . sub . γ to keep the weight centered and stable in relation to the electrodes . the control voltage combinations ± v x , ± v . sub . γ are applied to the four electrodes 11 , 12 , 21 , 22 via four high - voltage amplifiers 111 , 112 , 121 , 122 . these amplifiers are shown in fig3 as differential amplifier 111 , summing amplifier 112 and inverters 121 and 122 . in fig4 is shown how the dc control voltages are applied to the same electrodes used to detect position through the coils of a differential transformer . capacitances c 21 and c 11 , the difference whereof must be measured by the capacitive detectors , are connected in a bridge circuit driven by sinewave voltage vd , having an angular frequency ω d , that is also applied to weight 1 via lead 7 . the detector output signal v s is obtained in response to bridge unbalance signal being fed through amplifier 18 and synchronous demodulator 19 . referring now to fig5 the six silica plates 1 - 6 making up the test weight are metallized to provide two sets of mutually electrically insulated plates 1 - 3 and 4 - 6 ( three plates are included in each set ). electrical continuity subsists through the three plates of each set . each three - plate set is respectively driven to a pair of potentials (+ v p + v d ) and (- v p - v d ) that are symmetrical with respect to the frame potential . to this end sources (+ v p + v d ) and (- v p - v d ) are respectively connected to the two sets by two very flexible lead wires 7 and 8 . along each of the three axes of the accelerometer , the two pairs of electrodes are connected to the inputs of two capacitive detectors d 1 and d 2 . compared with the prior art just reviewed herein , and referring to fig6 the dc voltage differences ( due to the control and biasing voltages ) are identical to those obtained in fig2 . the new configuration of fig6 thus provides the same electrostatic force and torque , both of which are linear functions of the position control voltages . in fig7 are illustrated the servocontrols according to the invention ; they are based on the same principle as those of fig3 except that the controls in fig7 are simpler since each pair of opposite electrodes is supplied from a single control amplifier 30 or 31 . for example , the output of amplifier 30 is connected to both electrodes 11 and 21 . in fig8 is shown the operating principle of the invention as a capacitive detector and for applying dc control voltages to electrodes used for position sensing . the oppositely phased detection signals + v d derived very low internal impedance generators 32 , 33 are applied to opposite faces of the weight via flexible leads 7 and 8 and capacitors 36 , 37 having very high values ξ . rc networks 36 - 38 and 37 - 39 for coupling the dc bias voltages + v p and - v p and the ac voltages of sources 32 and 33 as well as the dc detection voltages provide further filtering of the bias voltage . in fig9 is illustrated the equivalent circuit for the operation of the circuit diagrammed in fig8 when the detection signals are at angular frequency ω d . the unbalance signal obtained at detection signal angular frequency ω d when the two capacitors c 11 and c 21 are unequal is amplified selectively by amplifier 40 having a feedback impedance z that is highest at angular frequency ω d . the stray or parasitic capacitance c p of the link between the electrodes and the detector input capacitor c d , taken together with resistors r , r &# 39 ;, capacitor c and the output impedance of control amplifier 41 , constitutes an impedance z p ( fig9 ) which does not disturb the detector balance and in practice has little effect on sensitivity . the dc control signal voltage ( v 11 - v 21 ) is applied to the electrodes by a circuit including resistors r , ra &# 39 ;, capacitances c , c p , c d , c 11 and c 21 , and amplifier 40 that is sufficiently selective to ensure that changes in v 11 ( or v 21 ) do not affect the measurement voltage v s delivered by the detector . the invention as just described , especially in its principle of operation illustrated by fig8 and 9 , applies to the realization of a single - axis accelerometer which can be one of the elements of a two - or three - axis system . in an alternative embodiment illustrated in fig1 , the cross - shaped test weight is replaced by a pendular insulating test weight 54 articulated about a hinge ( including for example a necked portion 56 ) fixed on end 55 that is integral with the accelerometer frame . the test weight includes metallized , opposite planar faces connected to the ± v d signal generators 51 and 52 in fig8 ; electrodes c 11 - c 21 of the test weight are connected to the capacitive detector 53 of the same figure . it is possible to use a metallic test weight in the inventive accelerometer , in which case the weight is connected to the capacitive detector of fig8 and the electrodes are respectively connected to the ± v d signal generators 51 and 52 in fig8 . the test weight of such an embodiment is thereby easier to manufacture , since no metallization step is required .