Controller with dynamic temperature compensation

• US 20070200004A1
• Filed: 02/27/2006
• Published: 08/30/2007
• Est. Priority Date: 02/27/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Smith, Gary, Wacker, Paul, Kasper, Gary
• Granted Patent: US 7,784,705 B2
• Time in Patent Office: Days
• US Class Current: 236/44.C
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity

Abstract

An electronic device such as an HVAC controller that accounts for internal heating in determining an environmental condition such as temperature or humidity in the space surrounding the HVAC controller. The HVAC controller may calculate a transient heat rise value that is based upon a powered time period and a first order time lag, especially during a time period before which the HVAC controller reaches a steady state temperature condition.

Claims

1. A method of dynamic temperature compensation in an electronic device, the method comprising the steps of:

measuring a temperature within the electronic device;

determining a transient heat change; and

determining a corrected temperature based on the measured temperature and the transient heat change.

2. The method of claim 1, wherein determining the transient heat change is at least partially a function of how long the electronic device has been powered.

3. The method of claim 1, wherein determining the transient heat change is at least partially a function of how long the electronic device has been powerless subsequent to having been powered.

4. The method of claim 1, wherein determining the transient heat change is at least partially a function of how long the electronic device has been powerless subsequent to having been powered a sufficient time to reach a steady state temperature condition.

5. The method of claim 1, wherein the electronic device comprises a housing, and the measuring step occurs within the housing.

6. A method of dynamic temperature compensation in an HVAC controller having a housing, the method comprising the steps of:

measuring a temperature within the housing of the HVAC controller;

calculating a transient heat rise; and

calculating a corrected temperature based on the measured temperature and the transient heat rise.

7. The method of claim 6, wherein the step of calculating a transient heat rise is carried out repeatedly at least until the HVAC controller reaches a steady state temperature condition.

8. The method of claim 6, wherein calculating a transient heat rise comprises calculating a transient heat rise based upon a mathematical model.

9. The method of claim 6, wherein the transient heat rise is calculated using the following formula:

${\mathrm{HeatRise}}_{i+1}={\mathrm{HeatRise}}_i+\left(1-{\mathrm{e<br><br>}}^{-\frac{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t}{\mathrm{tau}}}\right)*\left({\mathrm{HeatRise}}_{\mathrm{SS}}-{\mathrm{HeatRise}}_i\right),$

where;

HeatRise_i+1 is the transient heat rise;

HeatRise_i is a previously calculated transient heat rise;

Δ

t represents a time increment since calculating HeatRise_i;

tau represents a time constant; and

HeatRise_SS represents a steady state heat rise value.

10. The method of claim 9, wherein Δ

t is set equal to one.

11. The method of claim 10, wherein tau is set equal to 45 minutes.

12. The method of claim 6, further comprising a step of operating the HVAC controller in accordance with the corrected temperature.

13. The method of claim 6, further comprising a step of displaying the corrected temperature.

14. A method of dynamic temperature compensation in an HVAC controller having a housing, the method comprising the steps of:

measuring a temperature within the housing of the HVAC controller;

calculating a transient heat rise;

storing in non-volatile memory the transient heat rise;

storing in non-volatile memory a time parameter indicating when power is lost; and

calculating a corrected temperature based upon the transient heat rise and the time parameter.

15. The method of claim 14, wherein calculating a transient heat rise comprises calculating a transient heat rise based upon a mathematical model.

16. The method of claim 14, wherein the time parameter comprises a date and/or time stamp stored when the transient heat rise value is stored.

17. The method of claim 14, wherein calculating a corrected temperature comprises adjusting the transient heat rise to account for cooling while power is lost.

18. The method of claim 14, wherein the transient heat rise is calculated using the following formula:

${\mathrm{HeatRise}}_{\mathrm{new}}={\mathrm{HeatRise}}_{\mathrm{old}}+\left(1-{\mathrm{e<br><br>}}^{-\frac{T}{\mathrm{tau}}}\right)*\left({\mathrm{HeatRise}}_{\mathrm{SS}}-{\mathrm{HeatRise}}_{\mathrm{old}}\right),$

where;

HeatRise_new is the transient heat rise;

HeatRise_old is a transient heat rise value stored before power was lost;

T represents a time duration during which the HVAC controller was not powered;

tau represents a time constant; and

HeatRise_SS represents a steady state heat rise value.

19. A method of dynamic thermal compensation in an HVAC controller, the method comprising the steps of:

measuring a parameter within the HVAC controller;

calculating a parameter correction factor; and

calculating a corrected parameter value based on the measured parameter and the parameter correction factor.

20. The method of claim 19, wherein the measuring step comprises measuring a relative humidity within the HVAC controller.

21. The method of claim 20, wherein the calculating a parameter correction factor is based at least in part upon a temperature within the HVAC controller.

22. The method of claim 20, wherein the step of calculating a corrected parameter value comprises calculating a corrected relative humidity value in accordance with the formula:

RH_actual=RH_measured+(A+B*RH_measured)*HeatRise,

where;

RH_actual is the corrected relative humidity value;

RH_measured is the measured relative humidity value;

HeatRise represents a temperature rise inside the HVAC controller; and

A &

B are correction factors relating to a particular HVAC controller.

23. The method of claim 22, wherein A is set equal to 0.294 and B is set equal to 0.0294.

24. An HVAC controller having a housing, the HVAC controller adapted to:

measure a temperature within the housing;

determine a transient heat change; and

determine a corrected temperature based on the measured temperature and the transient heat change.

25. The HVAC controller of claim 24, wherein the HVAC controller is adapted to determine the transient heat change as a function of how long the HVAC controller has been powered.

26. The HVAC controller of claim 24, wherein the HVAC controller is adapted to determine as a function of how long the HVAC controller has been powerless subsequent to having been powered.