Balance with active heat flow control

Patent metadata

Field	Value
Publication number	US-10018500-B2
Application number	US-201615288373-A
Country	US
Kind code	B2
Filing date	Oct 7, 2016
Priority date	Oct 29, 2015
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

A balance ( 30 ) is a single unit with a weighing pan ( 21 ) enclosed in a weighing compartment ( 22 ). A housing ( 23 ) adjoins the weighing compartment. The balance housing contains a weighing cell compartment ( 24 ) enclosing a weighing cell, an electronics compartment ( 25 ) containing electrical and electronic circuit elements, a thermoelectric heat pump module ( 27 ) and a heat flow controller ( 28 ). The balance is equipped to determine a net heat flow (P net ) inside the housing in the direction from the weighing cell compartment to the electronics compartment. The heat flow controller uses the net heat flow as a control input to regulate the the thermoelectric heat pump module, arranged inside the housing. The control input is used to generate an active heat flow (P A ) with magnitude and direction for holding the net heat flow at a level equal to the rate of heat dissipation produced inside the weighing cell compartment.

First claim

What is claimed is:

1. A balance configured as a single unit and comprising:
a weighing compartment;
a weighing pan enclosed in the weighing compartment;
a balance housing, adjoining the weighing compartment and comprising:
a weighing cell compartment, enclosing a weighing cell;
an interstitial space, separated from the weighting cell compartment by a first interior wall; and
an electronics compartment, containing electrical and electronic circuit elements, separated from the interstitial space by a second interior wall;

a means for determining a net amount of heat flow P net inside the balance housing from the weighing cell compartment in the direction of the electronics compartment and for providing a signal corresponding to the magnitude and direction of the net amount of heat flow;
a heat flow controller, in the balance housing; arranged to receive the signal as a control input;
a thermoelectric heat pump module, configured as a Peltier module arranged in the interstitial space with a first side thereof thermally connected to the first interior wall and a second side thereof thermally connected to the second interior wall, the Peltier module operating in a heat pumping mode with the first side removing heat and the second side producing heat to generate an active heat flow P A with a magnitude and direction to hold the net amount of heat flow P net at a level that essentially equals the rate of heat dissipation produced inside the weighing cell compartment, where the Peltier module is regulated by an electric current driven therethrough from the heat flow controller; and
insulating material, filling the interstitial space surrounding the Peltier module with an amount of passive heat flow P i occurring through the insulating material; such that P net is defined by the equation:
P net =P A −P i .

2. The balance of claim 1 , wherein:
the Peltier module serves as the means for determining P net by being temporarily switched from the heat-pumping mode to a thermoelectric generator mode in which:
when a temperature difference ΔT I exists across the insulating material between the first interior wall and the second interior wall, the Peltier module generates a voltage signal U Seebeck according to the relationship
Δ T I =k 2 ×U Seebeck

and
the heat flow controller receives the voltage signal U Seebeck , as the control input and, using the further relationship:
Pi=k 1 ΔT I =k 1 k 2 U Seebeck

determines P net .

3. The balance of claim 1 , further comprising:
a third interior wall that adjoins the weighing cell compartment;
a boundary layer of insulating material having a thermal resistance R th , arranged between the third interior wall and the first interior wall; and
a pair of temperature sensors, placed, respectively, on the third interior wall and on the first interior wall;
such that the pair of temperature sensors serve as the means for determining P net by sending at least one temperature signal as the control input signal to the heat flow controller for calculating the heat flow through the boundary layer, which represents the net heat flow P net .

4. The balance of claim 3 , wherein:
the first of the pair of temperature sensors measures a temperature T 1 of the third interior wall and the second of the pair of temperature sensors measures temperature T 2 of the first interior wall, and
each of the temperature sensors sends a temperature signal to the heat flow controller, where the net heat flow P net is calculated according to the equation:

P
net

=

T
1

-

T
2

R
th

.

5. The balance of claim 3 , wherein:
the pair of temperature sensors comprises a pair of thermocouples, connected anti-serially with the junctions placed, respectively, on the third interior wall and on the first interior wall, so that the pair of thermocouples measure a temperature difference in which the temperature of the first interior wall is subtracted from the temperature of the third interior wall, and
the pair of thermocouples send a temperature difference signal ΔT to the heat flow controller, where the net heat flow P net is measured according to the equation:

P
net

=

Δ
⁢

⁢
T

R
th

.

6. The balance of claim 3 , further comprising
a second Peltier module, arranged to operate in the thermoelectric generator mode to do the following steps:
measure a first temperature T 1 of the third interior wall and a second temperature T 2 of the first interior wall;
generate a temperature difference signal ΔT with a magnitude and direction determined by subtracting the second temperature from the first temperature; and
send the temperature difference signal ΔT to the heat flow controller, and

where the heat flow controller calculates the net heat flow P net according to the equation:

P
net

=

Δ
⁢

⁢
T

R
th

.

7. The balance of claim 1 , wherein:
the electronics compartment is divided into a weighing electronics chamber for containing temperature-sensitive, primarily analog electronic circuits and a digital electronics chamber for containing primarily digital and power circuits that are less temperature sensitive.

8. The balance of claim 7 , further comprising:
a third interior wall, adjoining the weighing cell compartment;
a boundary layer of insulating material having a thermal resistance R th ; and
a fourth interior wall, such that the boundary layer of insulating material is between the third interior wall and the fourth interior wall and the weighing electronics chamber is located between the fourth interior wall and the first interior wall; and
a pair of temperature sensors, placed on the third interior wall and the fourth interior wall, the pair of temperature sensors operating as the means for determining the net heat flow P net by measuring the respective temperatures and sending at least one temperature signal to the heat flow controller, where the heat flow through the boundary layer is calculated and is used to represent the net heat flow P net out of the weighing cell compartment.

9. The balance of claim 1 , f

Assignees

• Mettler Toledo Gmbh

Inventors

• Bühler Stefan
• Mock Daniel
• Geiser Michael

Classifications

• G01G23/48 Primary

  Temperature-compensating arrangements (G01G1/14, G01G1/42, G01G3/18 take precedence) · CPC title

• F25B21/02

  using Peltier effect; using Nernst-Ettinghausen effect · CPC title

• F25B2321/0212

  of electric power, current or voltage · CPC title

• G01G21/22

  Weigh pans or other weighing receptacles; Weighing platforms · CPC title

• G01G21/286

  with windshields · CPC title