Calibration of electrical parameters in optically switchable windows
The embodiments herein relate to methods for controlling an optical transition and the ending tint state of an optically switchable device, and optically switchable devices configured to perform such methods. In various embodiments, non-optical (e.g., electrical) feedback is used to help control an optical transition. The feedback may be used for a number of different purposes. In many implementations, the feedback is used to control an ongoing optical transition. In some embodiments a transfer function is used calibrate optical drive parameters to control the tinting state of optically switching devices.
1. A method of calibrating an electrochromic device to produce an adjusted optical density at a specified tint state, wherein the adjusted optical density has a first variance from an intended optical density for the specified tint state, the method comprising:
(a) measuring one or more parameters of the electrochromic device, wherein the one or more measured parameters correlate with an unadjusted optical density at the specified tint state, the unadjusted optical density having a second variance from the intended optical density, the second variance being greater than the first variance;
(b) applying the one or more measured parameters to a transfer function to generate a calibrated drive parameter for the electrochromic device, wherein the transfer function was produced from a training set of electrochromic devices;
(c) configuring control logic for controlling one or more optical transitions and/or states in the electrochromic device, wherein the configuring comprises applying the calibrated drive parameter; and
(d) applying the calibrated drive parameter to the electrochromic device to induce the adjusted optical density at the specified tint state in the electrochromic device.
2. The method of claim 1 , wherein the adjusted optical density at a specified tint state is within about +/−0.07 from the baseline optical density.
3. The method of claim 1 , wherein the transfer function is time-variant and employs an input variable that accounts for the age of the device.
4. The method of claim 1 , further comprising applying the method to a plurality of electrochromic devices so that variation in optical density at the specified tint state of the plurality of electrochromic devices is reduced to less than about 0.1.
5. The method of claim 1 , wherein one or more measured parameters are selected from the group of parameters consisting of open circuit voltage, leakage current, sheet resistance, and temperature.
6. The method of claim 5 , wherein the one or more measured parameters includes temperature.
7. The method of claim 1 , wherein measuring the one or more parameters of the electrochromic device comprises automatically measuring the one or more parameters, without direct manual user intervention.
8. The method of claim 1 , wherein the transfer function models a linear time-invariant system between one or more input variables comprising the one or more measured parameters and one or more output variables comprising the calibrated drive parameter.
9. A method of calibrating an electrochromic device to produce an adjusted optical density at a specified tint state, the method comprising:
(a) determining a transfer function between one or more optical device parameters and a corresponding measured optical density for a training set of electrochromic devices;
(b) measuring the optical density of the electrochromic device for a plurality of hold voltages at the specified tint states ranging between clear and tinted states
(c) calculating one or more calibrated drive parameters using the transfer function; and
(d) configuring control logic by substituting one or more predetermined drive parameters with the one or more calibrated drive parameters.
10. The method of claim 9 , wherein, when used by the window control logic, the one or more calibrated drive parameters bring the optical density of the electrochromic device to within about +/−0.07 from an intended baseline optical density at a specified tint state.
11. The method of claim 9 , further comprising applying the method to a plurality of electrochromic devices such that use of the one or more calibrated drive parameters at each electrochromic device reduces the variation in optical density for the plurality of electrochromic devices to less than about 0.1 at a specified tint state.
12. The method of claim 9 , wherein one or more measured electrical parameters are selected from the group consisting of open circuit voltage, leakage current, and sheet resistance.
13. The method of claim 9 , wherein measuring the optical density of the electrochromic device is done automatically, without direct manual user intervention.
14. The method of claim 9 , wherein the transfer function models a linear time-invariant system between one or more input variables comprising the one or more measured electrical parameters and one or more output variables comprising the one or more calibrated drive parameters.
15. A method of calibrating an electrochromic device to produce an adjusted optical density at a specified tint state, the method comprising:
(a) determining a transfer function between one or more electrical parameters and a corresponding measured optical density of for a training set of electrochromic devices;
(b) measuring the optical density and one or more electrical parameters for a plurality of window tint conditions ranging between clear and tinted states
(c) calculating one or more calibrated drive parameters using the transfer function; and
(d) configuring control logic by substituting one or more predetermined drive parameters with the one or more calibrated drive parameters.
16. The method of claim 15 , wherein the transfer function is time-variant and employs an input variable that accounts for the age of the device.
17. The method of claim 15 , wherein, when used by the window control logic, the one or more calibrated drive parameters bring the optical density of the electrochromic device to within about +/−0.07 from an intended baseline optical density at a specified tint state.
18. The method of claim 15 , further comprising applying the method to a plurality of electrochromic devices such that use of the one or more calibrated drive parameters at each electrochromic device reduces the variation in optical density for the plurality of electrochromic devices to less than about 0.1 at a specified tint state.
19. The method of claim 15 , wherein one or more measured electrical parameters are selected from the group consisting of open circuit voltage, leakage current, and sheet resistance.
20. The method of claim 15 , wherein measuring the optical density of the electrochromic device is done automatically, without direct manual user intervention.
21. The method of claim 15 , wherein the transfer function models a linear time-invariant system between one or more input variables comprising the one or more measured electrical parameters and one or more output variables comprising the one or more calibrated drive parameters.
22. The method of claim 15 , wherein the transfer function is time-variant and employs an input variable that accounts for the age of the device.