Customers often ask us about the measurement uncertainty of our devices. Below are Delta C's official statements on these metrics.
Under ideal conditions, Delta C capacitive sensors have a precision of 25PPM water in oil.
Precision is a description of variability in measurement between identical samples. For our capacitive sensors, we calculate precision by taking a series of readings at a stable water content, then calculate the standard deviation of these samples.
Under ideal conditions, Delta C capacitive sensors have a repeatability of 25PPM water in oil.
Repeatability is a description of how closely measurements compare to each other under the same circumstances, using the same instrument. For our capacitive sensors, we calculate repeatability as the standard deviation of a series of measurements taken at a stable water content.
If the possible sources of systematic error have been calibrated for correctly, the accuracy of a Delta C capacitive sensor's measurements is equal to the precision: 25PPM water in oil.
Accuracy is a description of how closely a measured value matches the true value. Any systematic errors present in the measurement will lower the accuracy. For our capacitive sensors, possible systematic errors include slope, temperature compensation, and one-point or multi-point calibration.
Delta C supplies calibration values for common fluids. When measuring a unique fluid, slope and temperature compensation tests need to be done as per our calibration guidelines.
If slope, temperature compensation, and calibration have been accounted for correctly then no systematic error will be present, and the accuracy will be equal to the precision.
Under ideal conditions, Delta C capacitive sensors have a resolution of 50PPM water in oil.
Resolution is a measure of when there is reasonable certainty that two samples are considered to have distinct values.
For Delta C capacitive sensors, the statistical uncertainty is the standard deviation of a series of samples at a stable water content.
The point at which the statistical uncertainty ranges of two samples no longer overlap is considered the resolution of our capacitive sensors.