Differential pressure sensors and measures of accuracy

[KrisKringle]

Hello, first time poster here!

I'm looking at differential pressure sensors for low pressure applications and I'm confused by how the manufacturers describe their sensors' accuracy. I see it is common to describe accuracy as a percentage of the full scale span, %FSS, for example in Table 5, page 4 of Honeywell's RSC series' datasheet (https://sensing.honeywell.com/honeywell-sensing-trustability-rsc-series-data-sheet-32321348-c-en.pdf). How do I relate %FSS to an error in Pascals?

Is it correct to relate it to 1% of the ADC's output span? So if the sensor uses a 12 bit ADC, the error is equivalent to 1% of the 2^12 values?

Thank you in advance.

[RoGeorge]

My understanding is like this:

If the sensor range is from, let's say 20mbar to 50mbar, then the FSS (Full Scale Span) is 50mbar - 20mbar = 30mbar.  0.1% of 30mbar will be 0.03mbar.

If the sensors reads, let's say 25mbar, then the real pressure is guaranteed to be somewhere in the range 24.97..25.03mbar.

[KrisKringle]

Thank you, I see. What confuses me now is the attached figure below. It's from https://sensing.honeywell.com/pressure-sensor-glossary-of-terms-tn-008200-2-en-final-08jul11.pdf. It seems to be related to the sensor output there?

EDIT:
As they say in the same document:

Full Scale Span (FSS)–The algebraic difference between output signal measured at the upper and lower limits of the Operating Pressure Range. Also known as „Span‟ or ambiguously as „Full Scale Output‟. (See Figure 1.)

[RoGeorge]

I'm not sure what exactly is the question related to that chart.

Looking at the terminology pdf, in fig.2 are shown all types of errors.  According to note 6 in the datasheet

Note 6, Accuracy: The maximum deviation in output from a Best Fit Straight Line (BFSL) fitted to the output measured over the pressure range. Includes all errors due to pressure non-linearity, pressure hysteresis, and non-repeatability.

the max 0.01% FSS BFSL includes only the sources of errors drawn in yellow.  The 0.01% does not includes other error sources caused by e.g. offset errors or thermal errors.

[KrisKringle]

My confusion regarding the chart in fig.1 is due to the offset at the minimum pressure. How do I determine what 0.1 % of FSS is, if I only know the operating pressure range? I see from the datasheet (section 5.0 page 28) that the sensor offers zero correction based on internally stored calibration data. Should I simply assume the minimum pressure offset is zero?

If I understand you correctly, a +/- 1 kPa pressure sensor with  +/- 0.1% FSS accuracy corresponds to an accuracy of 2000 * 0.001 = 2 Pa? I.e a measured value of 500 Pa is in the range of 498-502 Pa?

Thank you.

[RoGeorge]

If I understand you correctly, a +/- 1 kPa pressure sensor with  +/- 0.1% FSS accuracy corresponds to an accuracy of 2000 * 0.001 = 2 Pa? I.e a measured value of 500 Pa is in the range of 498-502 Pa?

Yes, 498-502 Pa assuming offset error, thermal error and any other type of errors are zero.

The best thing to do is ask a support engineer from Honeywell, I never worked with those sensors.

[KrisKringle]

Thank you!