Mass measuring system

• US 4,429,574 A
• Filed: 10/29/1981
• Issued: 02/07/1984
• Est. Priority Date: 10/29/1981
• Status: Expired due to Fees

• Current Assignee: Gary Rachfalski, Robert C. Barry
• Original Assignee: Gary Rachfalski, Robert C. Barry
• Inventors: Barry, Robert C., Rachfalski, Gary
• Primary Examiner(s): Kreitman, Stephen A.
• Application Number:
  US06/316,507
• Time in Patent Office: 831 Days
• Field of Search: 73/580, 73/579, 177/210 FP
• US Class Current: 73/580
• CPC Class Codes: G01G 3/165 Constructional details

Abstract

An apparatus for measuring the precise sample mass and corresponding sample weight, being tolerant of and relatively insensitive to unwanted background environmental forces, while functioning independently of the force of gravity, uses a vibratory method and a feedback means to monitor and to sustain the sample mass in oscillation at the mechanical resonant frequency of the system in which the sample mass is introduced. The sample mass is forced to oscillate continuously by electromagnetic action, whereby the resultant motion is transmitted by springs and a transmission structure to supporting piezoelectric transducers. These transducers generate an output voltage signal representative of the sample pan'"'"'s motion, that is amplified and returned to an electromagnetic drive coil in order to sustain oscillation and maintain the closed-loop nature of this system. These oscillations are monitored and the associated frequency measurements used in calculating the sample mass. A microprocessor is employed to solve a series of complex equations for calibration parameters which dynamically describe not only system mass but also system damping and spring constant while monitoring environmental variables such as temperature to correct the calculations for their effects. The result is a digital display of sample mass in corresponding weight units.

Claims

1. A mass measuring apparatus comprising:

a base member;

a support means including a substantially horizontal surface for supporting a sample mass to be measured, said support means being substantially circular in horizontal cross section, the mass of said support means being distributed so that it increases radially outwardly from the center thereof at a rate greater than the square of the distance from the center;

spring means connecting said support means to said base member so as to allow substantially only vertical vibrating motion of said support means relative to said base member;

first transducer means for generating an electrical output signal in response to and representative of said vibratory motion of said support means;

second transducer means coupled to said support means for vibrating the same in response to said signal to thereby sustain said vibratory motion of said support means;

electronic circuit means including means for evaluating said signal and for generating a mass signal in response thereto representing the mass of said sample.

2. The apparatus as claimed in claim 1 wherein said first transducer means is comprised of a piezoelectric transducer.

3. The appartus as claimed in claim 1 wherein said first transducer means is comprised of a plurality of piezoelectric transducers equally spaced around said support means.

4. The apparatus as claimed in claim 1 wherein said base member is formed of a lower section and an upper section and wherein said spring means is comprised of a plurality of tension springs connected between said lower section and said support means and between said upper section and said support means.

5. The apparatus as claimed in claim 4 wherein said first transducer means is comprised of a plurality of piezoelectric transducers equally spaced around said support means, said piezoelectric transducers being located between and being acted upon by said lower and upper sections of said base member.

6. The apparatus as claimed in claim 1 wherein said spring means is comprised of a plurality of springs equally spaced around and being connected to the periphery of said support member.

7. The apparatus as claimed in claim 6 wherein the combined mass of said springs is substantially smaller than the mass of said support means.

8. The appartus as claimed in claim 1 wherein said support means is substantially frusto conically shaped.