• Not Answered

Reference Accuracy of 3051 with respect to Turndown

Dear Emerson Support

I need to confirm the calculation of Reference accuracy of 3051SCD2 Ultra Differential Pressure Transmitter. The datasheet says:

±0.025% of span;

For spans less than 10:1, ±(0.005 + 0.0035[URL/Span])% of span

So the question is what does it mean that Span is less than 10:1. Does it mean that when URL/Span <10 then we should use  ±(0.005 + 0.0035[URL/Span])% of span

and when URL/Span >10 we should use ±0.025% of span

Because what I understand that as we use a larger turn down ratio, the accuracy of the equipment goes down (gets worse). Can you please confirm this understanding?

1 Reply

  • Shaiq,
    Let's use an example for clarity.
    On a range 2 differential pressure sensor the URL is 250 inH2O.
    For spans of 25 inH2O up to 250 inH2O, the reference uncertainty would be 0.025% of span.
    For spans less than 25 inH2O, the reference uncertainty uses the equation above.
    At 20 inH2O span, your uncertainty would be 0.005 + 0.0035 * (250/20) = 0.04875% of span.