Maxim Integrated
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Notes on the Enclosure
The MAXREFDES103# is not an industrial-grade health band. It is intended for performance
demonstration and typical design guidance. Excessive opening and closing of the enclosure lid
may cause the tightness of the lid closure to be compromised. If this happens, it is recommended
that the lid be taped to the sides of the enclosure.
Solvents such as alcohol should not be used to clean the mesa sticker or the cover film since
solvents may cause damage to these items. The cover film on the sensors is provided to prevent
dirt or sweat from interfering with the optical components.
Time-Alignment Method for Comparing PPG Data to ECG Data
When comparing the PPG data from the MAXREFDES103# to the data from an ECG reference
device, there may be some time differences between the two data sets. Consequently, post-
processing of the data needs to be performed to time-align the PPG and ECG data sets, as
outlined in the following procedure:
1. Downsample the PPG data to 1Hz to match the sampling rate data of the ECG data.
2. Using the Matlab function xcorr, find the time_difference, which provides the maximum
correlation between the data sets.
•
If the time_difference is greater than zero, then crop the first time_difference seconds
from the PPG data set.
•
If the time_difference is less than zero, then crop the first time_difference seconds
from the ECG data set.
3. If one data set is larger than the other, crop the excessive data at the end so that both
data sets are the same size.
4. Crop the first 30 seconds from the data sets to remove data captured during initialization.
Figure 52. PPG and ECG data sets that have been time-aligned.
