Compensated load cell

• US 4,380,175 A
• Filed: 06/12/1981
• Issued: 04/19/1983
• Est. Priority Date: 06/12/1981
• Status: Expired due to Term

• Current Assignee: Mettler-Toledo Incorporated (Mettler-Toledo International Inc.)
• Original Assignee: Reliance Electric Company (ABB Limited)
• Inventors: Griffen, Neil C.
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US06/272,928
• Time in Patent Office: 676 Days
• Field of Search: 73/1 B, 73/765, 73/767, 73/862.65, 73/862.66, 73/862.67, 177/211
• US Class Current: 73/862.622
• CPC Class Codes: G01G 3/1406 combined with special measuring circuits

Abstract

A force measuring device comprising a load receiving platform supported by a multiple bending parallelogram beam type load cell is provided with a plurality of electrical strain gages. Strain gage elements mounted on one of the beams are displaced toward one side of the beam and strain gage elements mounted on the other beam are displaced toward the other side of the other beam. An appropriate resistor network is connected to at least one strain gage on one or both of the beams to correct for either longitudinal or transverse displacement of the load on the platform. To correct for both transverse and longitudinal displacement of the load a resistor network is connected to each of three of the strain gages. Suitable procedures for determining the values of the resistor networks in combination with the above structure are included.

Claims

1. A force measuring load cell arrangement comprising in combination two substantially parallel beam means, means for rigidly connecting one end of the beam means together, support means connected to said ends of the beam means, means for rigidly connecting the other ends of the beam means together, a force receiver supported by said other ends of the beam means, strain gages mounted on each of the beam means, at least one strain gage being mounted laterally toward one side of one of the beam means and at least one strain gage being mounted laterally toward the other side of the other of the beam means, means for connecting the strain gages in a bridge arrangement, a shunt resistor connected across each of the strain gages mounted on one of the beam means to cause the output of the bridge arrangement to accurately represent the magnitude of a force applied to the force receiver independently of the lateral position of the force relative to the beam means.

2. A force measuring load cell arrangement comprising two elongated beams having substantially parallel longitudinal axes, means for rigidly connecting one end of the beams together, support means for rigidly connecting the other ends of the beams together and to a force receiver, means for mounting strain gages on the beams, at least one strain gage on one of the beams being displaced toward one side of the beam in a direction transverse to the longitudinal axes of the beams, at least one strain gage on the other beam being displaced toward the other side of said other beam in a direction transverse to the longitudinal axes of the beams, means for connecting the strain gages in a bridge arrangement, means for connecting a resistor to at least one of the strain gages on at least one of the beams to cause the output of the bridge arrangement to accurately represent the magnitude of a force applied to the force receiver independent of any offset of the force relative to the beams in at least the transverse direction.

3. An arrangement as claimed in claim 2 wherein resistors are connected to two strain gages on one of the beams to cause the output of the bridge arrangement to accurately represent the magnitude of a force applied to the force receiver independent of the transverse position of the force relative to the beams.

4. An arrangement as claimed in claim 2 wherein resistors are connected to two strain gages on one of the beams and at least one strain gage on the other of the beams to cause the output of the bridge arrangement to accurately represent the magnitude of a force applied to the force receiver independent of the position of the force relative to the beams.

5. A force measuring load cell arrangement in accordance with claim 2 characterized in that the resistors connected to the strain gages mounted on one of the beams have substantially the same resistance.

6. A force measuring load cell arrangement comprising two substantially parallel beam elements, one end of the beam elements being connected together and to a support, means for connecting the other ends of the beam elements together, force receiving means supported by said other ends of the beam elements, two strain gages mounted on each beam, at least one strain gage being mounted toward one edge of one beam and at least one strain gage being mounted toward the other edge of the other beam, means for interconnecting the strain gages in a bridge arrangement, resistors connected to three of the strain gages to cause the output of the bridge arrangement to accurately represent the magnitude of a force applied to the receiver independently of the position of the force relative to the beam elements.

7. A method of compensating a force measuring load cell arrangement including two beams having substantially parallel longitudinal axes and supporting a force receiving member, the method comprising the steps of (1) placing at least one strain gage toward one side of one of the beams in a direction transverse to the longitudinal axes of the beams, (2) placing at least one strain gage toward the opposite side of the other beam in a direction transverse to the longitudinal axes of the beams, and (3) connecting a compensating resistor to at least one strain gage mounted on at least one of the beams to cause the response of the load cell arrangement to be independent of the location in at least the transverse direction of the force applied to the force receiving member.