Diagnostic method for a weighing cell

Patent metadata

Field	Value
Publication number	US-9964429-B2
Application number	US-201514864027-A
Country	US
Kind code	B2
Filing date	Sep 24, 2015
Priority date	Mar 28, 2013
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A force-measuring device ( 1 ) with a parallelogram linkage has a measurement transducer coupled to it. A coil ( 25 ) of the transducer has guided mobility in a magnet system ( 27 ) and can carry an electric current ( 24 ). A position sensor ( 21 ) detects the deflection of the coil ( 25 ) from a balanced position relative to the magnet system when a load is placed on the force-measuring device. The electric current ( 24 ) flowing through the coil ( 25 ), by way of the interaction between the coil and the magnet system, returns the coil and the movable parallel leg to the balanced position. A system-characterizing means ( 29 ) is established in a processor unit ( 26 ). The system-characterizing means and an unchangeable system reference means ( 30 ) are compared to determine the functionality of the device. The functionality is verified by the magnitudes of the electric current and the deflection of the coil from its balanced position.

First claim

What is claimed is:

1. A method for verifying a functionality of a force-measuring device which works according to the principle of electromagnetic force compensation, the force measuring device comprising a stationary parallel leg, a movable parallel leg which receives the load of a weighing object, two parallel guides that connect the stationary and movable parallel legs, a measurement transducer that is coupled to the movable parallel leg through a force-transmitting connection and that comprises a coil that is arranged with guided mobility in a magnet system and that can carry an electric current, a position sensor, arranged to detect a deflection of the coil from a balanced position relative to the magnet system, the deflection occurring as a result of placing a load on the movable parallel leg, such that an electric current flows through the coil by way of the electromagnetic force acting between the coil and the magnet system to return to, or to maintain in, the balanced position the coil and the movable parallel leg, which is connected to either the coil or the magnet system, and a regulating unit for regulating the amperage of the electric current in response to the position sensor signal such that the coil returns to the balanced position, the method comprising the steps of:
establishing, by means of a processor unit, at least one system-characterizing resource of the force-measuring device, and
comparing at least one unchangeable system reference resource, which is stored in a persistent memory file of the processor unit to the system-characterizing resource, the comparison resulting in a determination of the functionality of the force-measuring device; and
using a magnitude of the amperage and a magnitude of the deflection of the coil from the balanced position to verify the determined functionality,
wherein each of the at least one system-characterizing resource and the at least one system reference resource establishes a relationship between the amperage of the electric current and the magnitude of the coil deflection.

2. The method of claim 1 , wherein:
one of the at least one system reference resource represents the functionality of the force-measuring device at the time of an initial adjustment, that is, adjustment that:
took place during production or close to the completion of the force-measuring device; or
reflects the condition of a fault-free functionality of the force-measuring device.

3. The method of claim 1 , wherein:
either the at least one system-characterizing resource, the at least one system reference resource, or both, includes a system table that lists the respective values of the weight force of the applied load associated with different magnitudes of the deflection of the coil from its balanced position and with different amperages of the electric current, and/or a system function with at least one parameter and with at least the magnitude of the deflection of the coil and the amperage of the electric current as input quantities.

4. The method of claim 3 , wherein:
the at least one parameter of the system function is stored as a parameter table, wherein the at least one parameter of the system function is load-dependent.

5. The method of claim 3 , further comprising the step of:
determining the values of the system table, the at least one parameter of the system function, or both, by at least one of the steps of:
varying the deflection of the coil and measuring, at essentially the same time, the amperage of the electric current caused by the deflection of the coil; and
varying the amperage of the electric current and measuring, at essentially the same time, the deflection of the coil caused by the amperage of the electric current.

6. The method of claim 5 , wherein:
the step of determining the values of the system table, the at least one parameter of the system function, or both, is conducted both with and without a weight being applied to the movable parallel leg, wherein the weight is either an externally handled weight or a weight set in place internally by a handling mechanism.

7. The method of claim 1 , wherein:
each at least one system reference resource is established either individually for each force-measuring device or generically for a given type of force-measuring device.

8. The method of claim 1 , wherein:
the result obtained from the comparing steps is used to do at least one of the following:
to investigate a fracture, tear, or deformation of a pivot of the parallel-guiding mechanism;
to investigate a position change of the coil relative to an original position thereof; and
to investigate a position change of the position sensor relative to an original position thereof,
wherein the respective original positions are associated with the condition of the force-measuring device in which the system reference resource was established.

9. The method of claim 1 , further comprising the steps of:
establishing a trend line of the functionality, based on the currently determined system-characterizing resource and the previously established system-characterizing means; and
predicting the future functionality, based on the established trend line.

10. The method of claim 4 , further comprising the step of:
determining the values of the system table, the at least one parameter of the system function, or both, by at least one of the steps of:
varying the deflection of the coil and measuring, at essentially the same time, the amperage of the electric current caused by the deflection of the coil; and
varying the amperage of the electric current and measuring, at essentially the same time, the deflection of the coil caused by the amperage of the electric current.

11. The method of claim 10 , wherein:
the step of determining the values of the system table, the at least one parameter of the system function, or both, is conducted both with and without a weight being applied to the movable parallel leg, wherein the weight is either an externally handled weight or a weight set in place internally by a handling mechanism.

12. The method of claim 9 , wherein the future functionality is predicted for the time remaining until the next service of the force-measuring system.

13. A gravimetric force-measuring device, working according to the principle of electromagnetic force compensation, comprising:
a processor configured with instructions, stored on a non-transitory, computer-readable medium, to perform the method of claim 1 .

14. A non-transitory, computer-readable medium with instructions stored thereon, that when executed by a processor that is a part of a force-measuring device operating according to the principle of electromagnetic force compensation, perform the steps of claim 1 , by using, as input values, at least the amperage of the electric current and the magnitude of the deflection of the coil from a balanced position thereof, to issue a signal for initiating an action of the force-measuring device.

15. The computer-readable medium of claim 14 , wherein:
the instructions include a step of recalling, from a persistent memory file of the processor, a system reference resource and at least one system-characterizing resource.

Assignees

• Mettler Toledo Ag
• Mettler Toledo Gmbh

Inventors

• Schrag Daniel
• Rupp Daniel
• Trautweiler Christoph
• Burkhard Hans-Rudolf

Classifications

• G01G23/01 Primary

  Testing or calibrating of weighing apparatus · CPC title

• G01G7/04

  with means for regulating the current to solenoids · CPC title

• G01G7/045

  having a PID control system · CPC title