From process value to the right model: where your normal reading sits on the range (40–70 % FS is the golden
band), the real error at that point — the %FS trap — and a use-based verdict (process control vs compliance) with the exact
catalogue model to order. Built for wastewater online analysers in the tropics.
1Process duty
Results — range, operating point, error, model
Operating point
—%FS
Error @ normal
—
Peak headroom
—
Item
Value
Rule / limit
Status
2Why %FS bites at the low end
For a %FS instrument the absolute error is constant across the whole span.
Operating low on the range turns that fixed error into a large fraction of your reading.
Reading as % of FS
50 %
25 %
10 %
5 %
Relative error × (headline accuracy)
—
—
—
—
Order this duty
Item
Model / spec
Quote this duty's analyser at factory price
The model below at the manufacturer's ex-works price — our margin comes solely from the export tax rebate.
This sheet gives you the range and the error to defend the choice to your reviewer.
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Sources & parameter basis
[1]
Sino Analyzer accuracy guide — golden rule (operate upper half / two-thirds of span) with the 0–500 vs 0–100 bar ±0.5%FS example (3.6 % vs 0.7 % relative).
[2]
E+H / Jade Ant flow sizing — normal 40–70 %FS, min >10 %, max <90 %.
