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User Guide
This tool will calculate the total worst case & root sum squared pressure error band, long term stability, thermal effects error, room temperature accuracy or pressure value for a pressure sensing device.
Combine the main errors provided in pressure sensor and instrumentation product specifications to determine the total error band in any pressure unit. Choose between the total error band, or the root sum squared total error band for a more probable error figure.
Formulas
The formulas used by this pressure sensing errors calculator to determine each individual parameter are:
TEB = P · (Acc + TE + LTS)
RSS = (P2 · (Acc2 + TE2 + LTS2))1/2
LTS = (TEB / P) – Acc – TE
LTS = ((RSS / P)2 – Acc2 – TE2)1/2
TE = (TEB / P) – Acc – LTS
TE = ((RSS / P)2 – Acc2 – LTS2)1/2
Acc = (TEB / P) – TE – LTS
Acc = ((RSS / P)2 – TE2 – LTS2)1/2
P = TEB / (Acc + TE + LTS)
P = (RSS2 / (Acc2 + TE2 + LTS2))1/2
Symbols
- TEB = Total error value in pressure units
- RSS = Root sum squared total error value in pressure units
- LTS = Long term stability as a proportion of a pressure value
- TE = Thermal effects as a proportion of a pressure value over a specific temperature range
- Acc = Accuracy as a proportion of a pressure value at a fixed temperature typically room temperature
- P = Pressure value
Pressure
This is the pressure value used to derive the percentage accuracy or the pressure error. The pressure range of a pressure measurement device is often used when calculating the pressure error since the accuracy is typically defined as a percentage of full scale (%FS).
Accuracy
This is a proportion of the pressure range that defines the margin of error in measuring the true pressure value. This is usually specified as percentage of full scale for a fixed temperature, normally room temperature, and incorporates all linearity, hysteresis and repeatability errors.
It can also include zero and span setting errors, especially if it is pressure indicator of some kind, which has already been calibrated. It will some times include temperature errors and even stability in more accurate pressure sensing instruments such as pressure calibrators.
Thermal Effects
This is error caused by a change in temperature, and is usually specified as a total percentage error over a defined temperature range, often called the compensated temperature range, or operating temperature range.
Occasionally the temperature error is broken down into a separate zero & span thermal error, and those cases you would have to combine the two errors first before entering them into this calculator. Also the thermal errors are some times included in the accuracy figure, so if that is the case you can leave the thermal errors blank.
Stability
This is the long term stability or drift of a pressure sensing device which describes how much any measured value could change over a specified amount of time.
Not all pressure sensing products include the specification for stability of accuracy so leave this blank if its not mentioned anywhere. The long term stability is normally stated as a percentage of full scale range for a period of 1 year.
RSS Total Error Band (RSS TEB)
This is the total amount of pressure derived from the root sum squared of all the errors combined that a reading may deviate from the true pressure value.
It represents a more practical and realistic error taking into account the random nature of component errors.
Total Error Band (TEB)
This is the total amount of pressure that a reading may deviate from the true pressure value. Each component error is added together to determine the total error band.
In reality it is very rare that the maximum value of each component error would occur at the same pressure, temperature or time, so it is considered a very conservative figure, unlike the RSS TEB above which would provide a smaller and more probable margin of error to use.