Calculate a problem; those who can help, please do it. There are several methods
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It’s a calculation problem involving a double-flange level gauge. The height to be measured is 80 centimeters; the low density is 0.9, and the high density is 1.2. The density of silicone oil is assumed to be 1.0. Calculate what the measurement range is – that is, what is the range over which the instrument can measure? How many calculation methods are there? Those who can do the calculation, please help calculate it. Thank you!
No one has seen this post yet, not even my friends. How fast! Thank you so much!
Reply to 1# xqb213: Friend, this is basic knowledge for instrument technicians, :)
At the zero level, the space is filled with a low-density medium of 0.9; the density difference compared to silicone oil is -0.1, so the differential pressure is -0.8 kPa. At the full level, the space is filled with a high-density medium of 1.2; the density difference compared to silicone oil is 0.2, so the differential pressure is 1.6 kPa. Therefore, the range is -0.8 to 1.6 kPa
If the medium density changes, it is recommended not to use differential pressure for measuring the interface.
For ease of calculation, assume that the transmitter is installed at the lower flange: the range ΔP = H(ρ_high – ρ_low)g = 800*（1.2 – 0.9）*98 = 23520 Pa = 23.50 kPa； When at a low liquid level: P+=Hρlow g=800*0.9*98=70560Pa=70.56kPa ； P-=Hρ silicon g=800*1.0*98=78400Pa=78.4kPa ； P+-P-=70.56kPa-78.4kPa=-7.84kPa. The range is 23.5 kPa, with a measurement range of -7.84 kPa to 15.66 kPa.
Friend upstairs, I have a question: when it comes to dual-flange differential pressure level gauges, the transmitter’s zero point should take into account the static pressure generated by the silicone oil; then why is it still necessary to subtract the static head of the silicone oil during calculations?
In my opinion, the pressure generated when a tank is filled with a low-density liquid should be set at zero, while the pressure generated when the tank is filled with a high-density liquid should correspond to the full scale. According to the formula P = p_density1 * g * h1 + p_density2 * g * h2, where h1 + h2 = H; this formula is then applied in the system for conversion. Note: The issues related to the calculation of the cover and the lack of transducer calibration are not taken into account here