Process Engineering Division – Instrumentation and Automation Section – Daily Topics – Topic No. 2020-12-22
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Process Engineering Division – Instrumentation and Automation Section – Daily Topics – Topic No. 2020-12-22: Discussion topic: 334. When using a single-flange level gauge to measure the liquid level in an open container, the distances from the gauge to the highest and lowest liquid levels are respectively h1 = 1 m and h2 = 3 m. If the density of the medium being measured is ρ=980 kg/m3, determine: 1. What is the range of the transmitter? (5 points are given only to those who provide the correct answer; additional points are awarded for a correct calculation process or detailed explanation.)
A single-flange level gauge is used to measure the liquid level in an open container, with the distances from the gauge to the highest and lowest liquid levels being h1=1m and h2=3m respectively. If the density of the medium being measured is ρ=980 kg/m3, determine: 1. What is the range of the transmitter? Solution: ΔP = (h2 – h1)ρg = (3 – 1) × 980 × 9.807 = 19221.7 Pa. Answer: Select 1930mm for the transmitter range.
Range = (3–1)*1000*980/1000*9.8 = 19.208 kPa
Transmitter range = (h2 - h1)ρg = (3 - 1) × 980 × 9.807 = 19221.7 Pa.
△P=ρg(H2-H1)=980*9.8*(3-1)=19208 (N/Kg)=19600 Pa; thus, the transmitter’s range is 0 to 19600 Pa
Is there something wrong with the question? The distances from the instrument to the highest and lowest liquid levels are 1 m and 3 m respectively, which means that the single-flange level gauge is installed in the middle of the container, with the lowest liquid level being 3 m below the gauge. In that case, the range = density × gravity × h1 = 980 × 9.807 × 1 = 9611 Pa
Transmitter range: ΔP=（h2-h1）ρg=(3-1)×980×9.807=19.22KPa. The measurement range of the transmitter is set to ρgh1~ρgh2, with a lower limit of 9.6 KPa and an upper limit of 28.8 KPa
△P=ρg(H2-H1)=980*9.8*(3-1)=19208 (N/Kg)=19600 Pa; thus, the transmitter’s range is 0 to 19600 Pa
Transmitter range = (h2 - h1)ρg = (3 - 1) × 980 × 9.807 = 19221.7 Pa.