Abstract: A mass determination device includes a combination of an elastic element connected with a mass holder. The combination has a normalized temperature coefficient of frequency substantially equal to zero over a temperature range of intended use for the mass determination device, whereby mass determination accuracy of the device during temperature change in the range is enhanced. The elastic element has a first normalized temperature coefficient of frequency over the temperature range. A second normalized temperature coefficient of frequency over the temperature range attributable to the mass holder is determined. The first normalized temperature coefficient and the second normalized temperature coefficient are substantially counterbalanced over the temperature range, for example, through material selection and/or heat treatment of the elastic element and/or material or geometry variation of the mass holder.

Abstract: A micromechanical oscillating mass balance and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers. The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.

Abstract: A weighing apparatus includes a base supporting a cantilevered elastic member bearing a load platform. The interior of the elastic member is hollowed and is provided with first and second piezoelectric transducers mounted on respective opposed posts. The transducers are arranged substantially parallel to each other with a small gap between them and are coupled to an amplifier to form a "delay line" and a positive feedback loop, i.e. a natural oscillator.

Abstract: A method for measuring the masses of objects in any gravity environment, including microgravity or zero gravity. An object is placed on or attached to a platform that is movable back and forth along a single axis of motion. An actuator is used to oscillate the platform and is controlled to provide a variable spring force. Instantaneous displacement values are obtained and used to calculate the period of oscillation. Values representing the period, the tare mass of the platform, and the spring constant are then used to calculate the mass of the object. The method may use active damping, and may be varied so that the oscillations are angular rather than linear.

Abstract: A load sensing system inexpensively monitors the weight and temperature of stored nuclear material for long periods of time in widely variable environments. The system can include an electrostatic load cell that encodes weight and temperature into a digital signal which is sent to a remote monitor via a coaxial cable. The same cable is used to supply the load cell with power. When multiple load cells are used, vast inventories of stored nuclear material can be continuously monitored and inventoried of minimal cost.

Abstract: A system for determining the weight of a vehicle includes a first axle subject to a relatively fixed axle weight. Typically, this axle is a front steering axle for a tractor-trailer combination vehicle. The load on this axle is considered known as the load does not vary significantly during the operation of the vehicle. A first accelerometer is supported on the first axle and measures the vertical acceleration of the first axle producing a first signal. Each additional axle on the vehicle, including any single rear or tandem drive axles and any trailer axles, also supports an accelerometer. The accelerometers on each of these additional axles measure the vertical acceleration of its respective axle. Each of these additional accelerometers produces a signal representative of its respective axle accelerations and these signals are combined to produce a second signal. A processor determines the vehicle weight by comparing the second signal to the first signal.

Abstract: A quartz crystal resonator is excited in two different modes at the same time such that the mass change and the temperature change can be measured independently. In using such a quartz crystal the change in mass can be calculated accurately and in real time, independent of temperature effects.

Abstract: A micromechanical oscillating mass balance and method adapted for measuring minute quantities of material deposited at a selected location, such as during a vapor deposition process. The invention comprises a vibratory composite beam which includes a dielectric layer sandwiched between two conductive layers. The beam is positioned in a magnetic field. An alternating current passes through one conductive layers, the beam oscillates, inducing an output current in the second conductive layer, which is analyzed to determine the resonant frequency of the beam. As material is deposited on the beam, the mass of the beam increases and the resonant frequency of the beam shifts, and the mass added is determined.

Abstract: An electronic weighing apparatus includes a base which supports a cantilevered elastic member upon which a load platform is mounted. The free end of the elastic member is provided with a first piezoelectric transducer and a second piezoelectric transducer is supported by the base. Each transducer includes a substantially rectangular piezoelectric substrate and a pair of electrodes imprinted on the substrate at one end thereof. The transducers are arranged with their substrates substantially parallel to each other with a small gap between them and with their respective electrodes in relatively opposite positions. The electrodes of the second transducer are coupled to the input of an amplifier and the output of the amplifier is coupled to the electrodes of the first transducer. The resulting circuit is a positive feedback loop with a "delay line" in which a surface acoustic wave in one substrate is effectively induced into the other.

Abstract: The oscillation of an oscillator is automatically stopped during gas sampling, and the gas sampling is automatically stopped during the measurement of the frequency of the oscillator before and after the gas sampling, thereby making it possible to avoid the measurement error due to a change in resonance frequency by the effect of dynamic and static pressures applied to a filter paper holder mounted at the free end of the oscillator in the gas sampling, and to prevent the dislodgement and reentrainment of suspended particulates collected in the filter paper due to the oscillation acceleration. Accordingly, it is possible to accurately measure the mass of suspended particulates deposited on a filter paper compared with the conventional method in which the gas sampling and the measurement of the frequency are simultaneously and continuously performed while oscillating an oscillator.

Abstract: An electronic scale is disclosed having a device for recalibrating the scale from time to time after the scale is moved from the factory to a site of installation in order to adjust the scale for physical and/or environmental operating conditions which are different from those which prevailed at the factory when the scale was originally calibrated after the completion of manufacture and which have an adverse effect on the accuracy of the scale if the scale is not recalibrated under these conditions. The scale is provded with a device which adds a predetermined fixed weight to the load cell of the scale at any desired time or interval of time, and an electronic count indicative of this weight at the site of installation is compared with an electronic count of the same weight taken at the factory and stored in a memory, and the digital readout of the scale is then adjusted by an amount which is the same as the ratio of the original count of the weight and the count thereof taken at the site of installation.

Abstract: Disclosed is a balance with a first parallel guide (3, 3') which resiliently connector a load receiver (2) to an area (5, 5') fixed to the housing and which is resiliently deformed under the influence of the weight to be measured, and with a second, softer parallel guide (8) which is connected by its one end to the load receiver (2) and by its other (11) end via a force receiver which is at least approximately without displacement to the area (5, 5') fixed to the housing and which transfers as a result thereof a fraction of the force of the weight onto the force measuring receiver that both parallel guides (3, 3', 8) exhibit at least approximately the same height and the same length and are arranged close to one another laterally. The second parallel guide is advantageously locate between two partial areas (3, 5, and 3', 5') of the first parallel guide.

Abstract: In an inertial mass measurement instrument, an active force compensator compensates for inertial forces transmitted by an oscillating elastic element to a primary support of the instrument. The compensator applies equal and opposite compensating forces to the primary support along an effective line of action of the oscillating element. Application of the compensating forces result in a substantially zero net acceleration of the primary support and avoids measurement inaccuracies attributable to changes in properties of secondary support elements.

Abstract: A load cell, one end of the cell being mounted on a base and the other end of the cell being arranged for connection to a force applicator so that in operation applied loads are transmitted vertically to said other end to distort the cell, and wherein the cell houses a vibrating beam force sensor lying in a plane parallel to the base, the cell being so arranged that the vertical force produced by an applied load to the force applicator is translated into a horizontal force applied to the vibrating beam force sensor.

Abstract: In a load cell for a weighing machine, the load cell includes a vibrating beam force sensor clamped at its two ends to respective support parts of the load cell, and wherein each end of the sensor is clamped by a bolt having a head which traps the associated end of the sensor against a support part, the bolt having remote from its head a threaded portion engaged with a nut which tensions the bolt, and a portion of non-circular cross section having at least one cross sectional dimension which is greater than that of the threaded portion, the non-circular cross section portion of the bolt having been drawn through a hole in the support part which had a diameter less than said one cross sectional dimension. This reduces the production of forces parallel to the plane in which clamping is required.

Abstract: The invention is directed to a counting scale which implements a load cell assembly for the measurement of weight used in counting calculations. A load cell in such an assembly has a beam structure with beams positioned parallel to each other in at least one plane. Generally, these parallel beams are attached to a stationary base and have sensing means attached between the two beams and the base. These sensing means are preferably resonators which have resonant frequencies that vary in response to an applied force on the load cell. A controller is included in the assembly to drive these resonators, convert their frequency outputs to digital values, and correct for various environmental effects, to obtain an accurate weight measurement for use in the counting scale.

Abstract: An apparatus for measuring a force or load comprising a vibratory beam which vibrates back and forth at a resonant frequency. The beam has first and second end nodal points and first and second ends adjacent to the first and second nodal points. The first end of the vibratory beam is coupled to the load for applying a stress to the vibratory beam that determines the resonant frequency at which the beam vibrates. In addition, masses are coupled to the beam intermediate of the first and second ends. The masses are arranged symmetrically on opposite sides of the beam and reciprocate at the resonant frequency. The reciprocatory masses are located at a position along the beam at which the greatest back and forth vibration of the beam at the resonant frequency occurs. Alternatively, a pair of vibratory beams are provided. The beams are coupled together at opposite ends to form a tuning fork, each beam having a portion which vibrates back and forth at a resonant frequency.

Abstract: An apparatus measures the mass of a tube and liquid contained in the tube. A stiff beam is fixed at one end and connected to the tube with a magnet thereon. An electric circuit generates a current pulse which vibrates the beam and tube and induces a natural response therein. Movement of the magnet on the beam induces a current in the circuit with the induced current having a frequency of oscillation equivalent to the natural frequency of vibration of the tube and liquid in the tube. The electric circuit includes a comparator and a counter, with the comparator receiving the current induced by movement of the magnet and supplying a pulse signal to the counter having a period equal to the period of oscillation of the beam and the tube. The counter triggers the generation of an additional current pulse after a predetermined number of cycles of the induced current are counted. The current pulses are generated at a frequency lower than the frequency of the natural vibratory response of the beam and the tube.

Abstract: The invention is a load cell for the measurement of force, independent of displacement, created by means such as weight, acceleration, pressure, and the like. The load cell has a beam structure with beams positioned parallel to each other in at least one plane. Generally, these parallel beams are attached to a stationary base and have sensing means attached between the two beams. In operation, deflection of one beam creates a response in the sensing means due to the relative action or deflection in the second beam.

Abstract: A weight measuring device includes two piezoelectric elements. The first piezoelectric element induces vibration in an object to be measured, and the second one detects the reaction force of the object generated by the vibration. This force is detected by a voltage monitor circuit as an output voltage from the second piezoelectric element. From the voltage which has been detected, the weight of object is determined. The device further includes an absorbing element to absorb unnecessary piezoelectric strain in reaction force generated when the object vibrates. The invention provides a compact weight sensor which can be produced at low cost, and which can measure weight with high accuracy.

Abstract: A system and method for measuring particulate concentrations. The system includes a substantially planar, peripherally supported filter for capturing the particulates, an oscillator for oscillating the filter substantially perpendicular to its planar surface, and a sensor for measuring the frequency of oscillation.

Abstract: A load cell device includes a load cell structure formed of a suitable metal and including vertically spaced apart, generally parallel horizontal elements integrally formed with longitudinally spaced apart, generally parallel vertical elements. Flexures interconnect each horizontal element with the vertical elements. A bending beam extends between and is interconnected with the horizontal or vertical elements. When a load is applied vertically and perpendicularly to one of the horizontal elements, the load cell structure will elastically deform as a parallelogram to thereby transfer shear force to the bending beam to cause shear-induced bending of the latter. Strain gages or frequency resonator crystal elements sense the shear-induced bending and are embodied in electronic circuitry which produces an output signal caused by deformation of the bending beam. The electronic circuitry is operable to convert the output signal to a perceptive force readout.

Abstract: A spring structure for a weight scale is described which is assembled from four extruded aluminum parts. The structure readily lends itself to the addition of a platform for placing weights and its deflection resulting from a weight is essentially invariant to the location of the weight on the platform. The sensor which converts deflection of the structure into an electrical signal includes two conducting plates, attached to the structure, which constitute a variable capacitor. The variable capacitor is part of a self-excited oscillator circuit which yields a frequency which is accurately related linearly to the value of the weight. Means are provided for distorting one of the capacitor plates to provide further improvement of invariance to weight location on the platform.

Abstract: The invention is a load cell for the measurement of force, independent of displacement, created by means such as weight, acceleration, pressure, and the like. The load cell has a beam structure with beams positioned parallel to each other in at least one plane. Generally, these parallel beams are attached to a stationary substrate and have sensing means attached between the two beams. In operation, deflection of one beam creates a response in the sensing means due to the relative action or deflection in the second beam.

Abstract: The present invention concerns a process and a device for carrying out the process for weight determination of the contents of containers (5), for example for garbage. Two swivel arms (2) that are lifted by hydraulic devices (3) are mounted on a garbage collecting vehicle (1). The container (5) is carried by a fork (4). Integrated into the swivel arm (2) is a force measuring apparatus that comprises two flexural members (7) supporting the main load, two spring tongues (8), and a force transducer (11) that is installed between two stilts (12) between the spring tongues (8). The flexural members (7) and the spring tongues together form an elastic stepdown; the force transducer (11) thus only measures that part of the total load flowing through it as given by the stepdown. Further, a gradient meter (16) is mounted on the swivel arm (2), that has the same action line W as the force measurement device integrated in the swivel arm (2).

Abstract: A weighing scale includes a vibratory string force measuring device (1) the frequency of which varies as a function of the applied load. The load signal from the vibratory string device is supplied to a microprocessor (8) where it is processed with a first frequency signal supplied by a temperature-responsive first quartz oscillator (9), thereby to produce a load measurement output signal (GW), the first frequency signal serving also as the clock signal for the microprocessor. The microprocessor also compares the first frequency signal with a second frequency signal supplied by a temperature-independent second quartz oscillator (11), thereby to produce a temperature compensation signal (TW).

Abstract: An electronic weighing system is disclosed which, employs spaced cylindrical dielectric rings as the load measuring transducer. A support structure is provided to linearly vary the spacing between the rings responsive to applied load which will linearly vary the resonant frequency of the rings. In an active mode, each microwave load cell is excited by an unstable oscillator, the dielectric rings stabilizing the oscillator at a resonant frequency which is proportional to their spacing. The oscillation frequency of the load cell is measured and used to compute the magnitude of the load applied to the cell based upon a predetermined relationship between output frequency and load. A plurality of multiplexed load cells may be employed. In a passive mode, a voltage controlled oscillator generates a microwave signal which linearly sweeps a preset frequency band. The sweeping signal is applied across the dielectric rings which generate a detectable pulse at their primary resonant frequency.

Abstract: A weighing system and method having stable measurement resolution for measuring gems and other light masses. The system includes circuitry for correcting errors in the measured value of the masses due to off-center placement on the system's holding pan. The weighing system uses a plurality of transducers about the pan to measure the weight of the mass, and includes circuitry for converting the transducer signals to signals having unknown frequencies. Circuitry is also provided for determining the unknown frequencies with an approximate stable or fixed resolution, despite wide variations in the unknown frequency. In a preferred embodiment, the number of cycles on the unknown frequency is counted and counting begins and ends of the rising edges of the unknown frequency signal. The determination of which unknown frequency edge ends the counting operation is made by monitoring a known frequency counter.

Abstract: A scale for fast determination of weights including a platform and a load cell transducer. Output of the transducer is converted to a digital signal, processed by a low pass digital filter, and weights computed as a function of the sequence of digital signals by means of an algorithm which compares a first estimate of the weight to the break points of a postal rate chart and uses the first estimate if it is not within a predetermined distance of a break point, and otherwise determines a second, more accurate estimate. The platform and transducers are combined to form a structure which does not have any significant resources below the cut-off frequency of the filter.

Abstract: A removable transport mechanism for a vibrating tray scale for conveying flats on off of the platform of the tray. The removable drive mechanism has belts trained about rollers that can be readily replaced after they become worn. The transport mechanism has a floor that supports the conveying mechanism and the floor is attached to the vibrating tray scale by springs so as to be readily removable.

Abstract: A force transducer includes a force transmitting mechanism comprising a reference member which is stationary during measurement, a force input member and two holders adapted to hold a transducing element and to apply a force thereto at least approximately perpendicular to the force applied to the force input member. The force transmitting mechanism comprises two spaced, metallic plate members connected with each other at the holders by electrically insulating pins forming part of the holders. Eyelets of the electrically conducting transducing element are fixedly held by the holder pins.

Abstract: A control for a transport mechanism vibrating tray scale that conveys flats on and off of the platform of the tray. The scale supports a follower plate that has ramps which contact with the rollers of the transport mechanism. The follower plate is also in contact with a cam which upon rotation cause the follower plate to move within the scale. As the follower plate is moved, the rollers of the transport mechanism will move into and out an opening of the scale platform, depending upon direction of movement of the follower plate.

Abstract: A liquid level sensing apparatus for detecting leaks in storage tanks. A buoyancy member is at least partially immersed in the liquid, suspended from a pivoted, counterbalanced, parallelogram support arrangement with a radio frequency target sensing element for electrical readout of displacement. Two such apparatus are incorporated in a system with a provision for measuring a portion of the liquid of the tank in isolation from the remainder, in order to provide for temperature compensation.

Abstract: An electronic fish scale having a spring connected to a hook to which the fish or other item to be weighed is attached. Attaching the weight to the hook causes linear displacement of the spring. A rigid coupling is attached to the spring and connected to a variable resistor such that movement of the spring results in a change in the effective resistance of the variable resistor. Electronic circuitry is interconnected with the variable resistor such that a signal is generated which is indicative of the effective resistance of the variable resistor. The generated signal is sampled and processed at a microprocessor having stored data corresponding to the weight equivalent to the variance in the variable resistor-dependent signal. A display receives a signal output from the microprocessor and displays and weight measured.

Abstract: A weighing in motion (WIM) apparatus and method in which scale platforms are provided exhibiting a high rigidity selected to achieve a relatively high natural frequency response characteristic. These platforms are combined with instrumentation wherein load cell derived signal outputs are digitized at a conversion or sampling rate effective to permit an identification of amplitude data correlative to vehicle weight. In particular, the sampling rate is selected so as to isolate and detect peak amplitude output of the system which is directly correlatable to truck weight. The invention derives from a recognition that, during the dynamics of movement of a vehicle such as a truck over the rigid scale platform structures, there occurs a decoupling of the mass of the truck from the scale permitting its response to the weight of the truck without significant loss of natural frequency bandwidth.

Abstract: A vibration type force detector comprising: a string to which a force to be measured is applied in the direction in which the string is tensioned; a driver for causing the string to vibrate at its natural frequency and simultaneously producing a series of pulses at a frequency in synchronism with the vibration of the string; a gate to which the series of pulses are applied; a counter for counting the series of pulses that have passed through the gate; means for providing a gating time determined in accordance with the result of the counting of the counter; and a controller for controlling the gate in accordance with the gating time. The gating time providing means is so arranged that as the vibration frequency of the string increases, the gating time lengthens.

Abstract: A vibrating force sensor comprising a metallic strip having three metallic coplanar beams (20, 21, 22). The sensor also includes capacitive transducers (30, 31) for driving the beam or beams into flexural vibration in a plane normal to their common plane and for detecting changes in the frequency of vibrations in response to changes in tension applied to the sensor. Drive and detect electrodes (50, 51) are formed on the surface of an intermediate insulating layer (70) in turn located on the surface of a shielding layer (71) of conductive material.

Abstract: Apparatus and method of determining the mass of an article by the shift of the period of oscillation of a flexibly mounted tray. An article whose mass is to be determined is placed upon the tray which is caused to oscillate and the period of harmonic motion is calibrated. This period is compared against the period of harmonic motion when there is no article upon the tray, and the difference, or shift, in frequency, allows a determination of the mass of the article. The tray is supported by a plurality of flexible members having parallelogram configuration that eliminates bending stresses.

Abstract: A force measuring device mainly used as a weighing device, comprising first and second horizontal cantilever members disposed parallel with each other in a common vertical plane, a weighing cradle attached to the free end of the first member, and a metal string stretched between the free ends of both members. The string is placed between a pair of magnetic poles so that it vibrates at its inherent frequency functionally relating to its tension and, therefore, a load applied to the weighing cradle. The frequency of the string is measured and the value of the applied load is calculated therefrom by an electronic calculating circuit. In order to overcome a problem of frequency deviation caused by variation in the spring constants of both cantilever members due to variation in the surrounding temperature, the inventive device includes a temperature sensor and arithmetic circuitry for applying compensation for the error due to the temperature change to the calculation of the applied force.

Abstract: Apparatus and method of determining the authenticity of a signal indicative of the mass of an article being weighted. The article is placed upon the platform, and the platform is caused to oscillate and the period of harmonic motion is measured. One of or both the frequency of oscillation and amplitude of the transducer signal is monitored for purposes of determining authentication.

Abstract: Apparatus and method of determining the mass of an article by the shift of the period of oscillation of a flexibly mounted tray. An article whose mass is to be determined is placed upon the tray which is caused to oscillate and the period of harmonic motion is calibrated. This period is compared against the period of harmonic motion when there is no article upon the tray, and the difference, or shift, in frequency, allows a determination of the mass of the article. The tray is supported by a plurality of flexible members having parallelogram configuration that eliminates bending stresses.

Abstract: The invention provides an electronic weighing instrument of the electrostatic capacity type which eliminates an influence on a measured weight value of a rate of change in oscillation frequency which is caused by environmental conditions such as an ambient temperature or a humidity. The electronic instrument comprises a pair of capacitors having capacitances which are differentially varied by a displacement caused by a load. The capacitors are alternately connected to the oscillating circuit at predetermined intervals of time, and each time either of the capacitors is connected to the oscillating circuit, an oscillation frequency is fetched from the oscillating circuit. Then, a difference and a sum between two different oscillation frequencies successively fetched from the oscillating circuit are calculated, and the difference is divided by the sum to obtain a measured weight value.

Abstract: A liquid level sensing apparatus for detecting leaks in storage tanks. A buoyancy member is at least partially immersed in the liquid, suspended from a pivoted, counterbalanced, parallelogram support arrangement with a radio frequency target sensing element for electrical readout of displacement. Two such apparatus are incorporated in a system with a provision for measuring a portion of the liquid of the tank in isolation from the remainder, in order to provide for temperature compensation.

Abstract: Transport and drive apparatus and method for use in determining the weight of an article. An article whose mass is to be determined is transported upon the plan of a weighing scale by a combination of rollers attached to the tray and drive rollers received within an opening of the tray. A reversible motor is used to provide drive to a conveyor rollers for transporting mail pieces onto the tray and for withdrawing the rollers upon reverse drive for purposes of weighing.

Abstract: A locking mechanism for securing the tray of a scale during the transporting of flat articles, such as envelopes, onto and across the tray of the scale. When a flat has been placed in a position for weighing, the conveying mechanism is put into an inoperative mode and causes the locking mechanism to release the tray. After the article is weighed, the conveying mechanism is placed into the operating mode and acts upon the locking mechanism to cause it to once more secure the tray.

Abstract: Apparatus for measuring force, useful in a weighing scale for example, includes a parallelogram-like load cell structure that deflects in response to application of the force to be measured, and a pair of force-sensitive crystal resonators, attached to cantilever sensor beams forming part of the structure for sensing the deflection of the load cell structure. The two resonators are attached to the sensor beams such as to be placed in tension and compression, respectively, upon deflection of the structure and thereby cause their vibration frequency to increase and decrease, respectively, with increases in applied force. The difference between the two frequencies, which varies substantially linearly with changes in applied force and is inherently digital in nature, is used as a measure of the force applied to the load cell structure.

Abstract: A suspension system for an inertial balance constrains the weighing platform when oscillated to undergo uniform linear motion, thereby ensuring high measurement accuracy. The suspension system includes a supporting framework and a first plurality of elongate elastic support members for suspending the weighing platform from the supporting framework. The elongate support members are disposed in a common plane when the weighing platform is at rest and their inner ends intersect at a first common point to which the weighing platform is firmly linked. A second plurality of such elongate support members is similarly disposed in a second common plane parallel to but spaced from the first common plane. A stiff connecting rod joins the intersection points of the two pluralities and also serves to support the weighing platform and, in conjunction with a feedback system, serves to induce and maintain the weighing platform in oscillation at a resonant frequency dependent upon mass loading.

Abstract: Oscillating and alternatively locking apparatus and method of determining the mass of an article by the shift of the period of oscillation of a flexibly mounted platform. An article whose mass is to be determined is placed upon the platform. The platform is caused to oscillate and the period of harmonic motion is calibrated. This period is compared against the period of harmonic motion when there is no article upon the platform, and the difference, or shift, in frequency, allows a determination of the mass of the article. A reversible motor is used to provide drive to a conveyor for transporting mail pieces onto the tray and for causing oscillation of the tray for purposes of weighing.

Abstract: Oscillating and alternatively locking apparatus and method of determining the mass of an article by the shift of the period of oscillation of a flexibly mounted platform. An article whose mass is to be determined is placed upon the platform. The platform is caused to oscillate and the period of harmonic motion is calibrated. This period is compared against the period of harmonic motion when there is no article upon the platform, and the difference, or shift, in frequency, allows a determination of the mass of the article. A reversible motor is used to provide drive to a conveyor for transporting mail pieces onto the tray and for causing oscillation of the tray for purposes of weighing.

Abstract: Improved shaped glass elements having very low thermal coefficients of elastic modulus are provided for use as measuring means in balances for determining the mass of objects with a high degree of resolution. A particularly preferred form of the invention id fabricated from a glass consisting of 60.6% SiO.sub.2, 14.7% B.sub.2 O.sub.3, 8.94% Al.sub.2 O.sub.3, 4.72% Na.sub.2 O and 10.98% BaO, by weight.