AUTOMATIC ANALYTE SENSOR CALIBRATION AND ERROR DETECTION
Systems and methods are provided that address the need to frequently calibrate analyte sensors, according to implementation. In more detail, systems and methods provide a preconnected analyte sensor system that physically combines an analyte sensor to measurement electronics during the manufacturing phase of the sensor and in some cases in subsequent life phases of the sensor, so as to allow an improved recognition of sensor environment over time to improve subsequent calibration of the sensor.
1 . An analyte sensor system comprising:
a continuous analyte sensor operable to obtain measurements indicative of analyte levels in a body of a host; and
a sensor electronics unit in communications with the continuous analyte sensor and configured for use in retrospectively calibrating the continuous analyte sensor by:
(i) generating an actual analyte sensor signal from the obtained measurements indicative of analyte levels, the actual analyte sensor signal extending over a first period of time;
(ii) identifying a start point and an end point of an artifact in the actual analyte sensor signal;
(iii) replacing the artifact with a predicted analyte sensor signal;
(iv) evaluating a difference between the predicted analyte sensor signal and the actual analyte sensor signal at the start point and the end point; and
(v) using the differences as a feedback signal to correct the predicted analyte sensor signal and repeat (iii) using the corrected predicted analyte sensor signal.
2 . The analyte sensor system of claim 1 , further comprising correcting the predicted analyte sensor signal by distributing the differences over a duration of the predicted analyte sensor signal to eliminate discontinuities in the corrected analyte sensor signal.
3 . The analyte sensor system of claim 2 , further comprising distributing the differences evenly over the predicted analyte sensor signal.
4 . The analyte sensor system of claim 2 , further comprising distributing the differences over the predicted analyte sensor signal using a weighted average.
5 . The analyte sensor system of claim 1 , wherein a duration of the artifact is less than 40 minutes.
6 . A system for monitoring data relating to analyte levels, comprising:
a continuous analyte sensor unit configured to prepare data relating to analyte levels;
a wireless transmitter operatively associated with the sensor and being configured to wirelessly transmit the data relating to the analyte levels; and
at least one display device configured to receive the transmitted data relating to the analyte levels, wherein the wireless transmitter is further configured to transmit a calibration request to the display device at a prescribed frequency that is determined based at least in part on an availability of pre-existing calibration information.
7 . The system of claim 6 , wherein the prescribed frequency is a default frequency if no pre-existing calibration information is available.
8 . The system of claim 6 , further comprising transferring calibration coefficients from a memory in the sensor unit to the transmitter.
9 . The system of claim 8 , further comprising transferring additional information for the memory to the transmitter, the additional information including at least one item selected from the group including a sensor lot number, a sensor expiration date, and sensor authentication information.
10 . The system of claim 8 , wherein the transmitter stores a default set of calibration coefficients and wherein transferring calibration coefficients from the memory to the transmitter includes transferring difference values between the calibration coefficients and the default set of calibration coefficients.
11 . The system of claim 10 , wherein the default set of calibration coefficients includes a first ordered list of paired values each specifying a coefficient identifier and a calibration coefficient value, wherein the difference values are provided as a second ordered list of paired values each specifying a coefficient identifier and a difference between a value of a calibration coefficient and a value of the default calibration coefficient.
12 . The system of claim 6 , wherein the prescribed frequency is further determined based at least in part on a type of application that receives the calibration request on the display device.
13 . A system for monitoring data relating to analyte levels, comprising:
a continuous analyte sensor unit configured to prepare data relating to analyte levels, the analyte sensor unit including a sensor having a working electrode and a reference electrode and a memory element electrically coupled to the working electrode for receiving power and data signals;
a wireless transmitter operatively associated with the sensor and being configured to wirelessly transmit the data relating to the analyte levels; and
at least one display device configured to receive the transmitted data relating to the analyte levels, wherein the wireless transmitter is further configured to:
periodically interrogate the sensor for a response indicating that the sensor is a new sensor; and
if the response indicates that the sensor is a new sensor, request calibration coefficients stored in the memory element by causing signal pulses to be applied to the memory element, the signal pulses having a predetermined voltage greater than a nominal operating bias voltage of the sensor.
14 . The system of claim 13 , wherein the memory element includes a short-term charge storage device to power the memory element while communicating the calibration coefficients to the transmitter.
15 . The system of claim 13 , further comprising communicating an end-of-life indicator to the memory element indicating that the sensor has expired, the indicator being stored in the memory element and preventing re-use of the sensor.
16 . The system of claim 13 , wherein the wireless transmitter is further configured to periodically interrogate the sensor by periodically waking up from a sleep state and if the response indicates that the sensor is not new sensor, returning to the sleep state.
17 . A system for monitoring data relating to analyte levels, comprising:
a continuous analyte sensor unit configured to prepare data relating to analyte levels;
a wireless transmitter operatively associated with the sensor and being configured to wirelessly transmit the data relating to the analyte levels; and
at least one display device configured to receive the transmitted data relating to the analyte levels and to provide the transmitter with calibration data provided to the display device by a user, the display device being further configured to:
receive biometric data of the user;
evaluate the biometric data and the calibration data provided to the display device by the user to determine if an incompatibility exists between the biometric data and the calibration data;
if an incompatibility exists, generating an error message; and
if no incompatibility exists, communicating the calibration data to the transmitter.
18 . The system of claim 17 , wherein evaluating the biometric data and the calibration data includes evaluating the biometric data, the calibration data and analyte sensor data received from the analyte sensor unit to determine if an incompatibility exists between the biometric data and the calibration data.
19 . The system of claim 17 , wherein the biometric data includes a heart rate of the user.
20 . The system of claim 17 , wherein the calibration data is manually entered into the display device by the user.