High Residuals in pH Data The data shown above come from a SeapHOx V2 (red) and Deep SeapHOx V2 (blue) deployed next to one another in a dynamic estuarine environment. Regular pH validation samples were collected throughout the time-series. According to the 0.05 pH accuracy spec of each sensor, there really isn’t much to be concerned about: both sensors agree with one another within spec (sensor residual average = 0.038 pH) and the overall gap between each sensor’s data is minuscule compared to standard glass electrodes. Furthermore, the difference between validation samples and the Shallow SeapHOx V2 is within spec when considering the accuracy of the samples themselves. That being said, ISFET pH sensors can and should do better, and recent optimizations in Sea-Bird Scientific’s calibration process show that this is true.
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