Double-flange transmitter for level measurement – migration issue.
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Why is it said that when using double-flange measurement for closed containers, negative migration must be employed regardless of the installation position of the transmitter? How is this amount of migration calculated? Is it related to the installation location of the transmitter?
If the original poster is not from the instrumentation field, it’s hard to explain. If so, it’s recommended that you look up information on your own; you can find it by searching on Baidu.
Those who have graduated from technical schools don’t need to teach this, hey!
Since the double-flange level transmitter transmits pressure through capillaries, silicone oil is present in the capillaries on the negative pressure side. When the liquid level is at zero, the pressure on the negative pressure side is higher than that on the positive pressure side; therefore, negative migration is required.
After installation, there is no pressure; as long as it shows zero pascals, that’s fine
1. The amount of migration is not calculated; just use the value shown in the table for negative migration. 2. Instead of asking this question, it’s better to move the transmitter up or down and see what happens!
The installation height of the transmitter has no relation to migration, but if there is no medium in the container for an extended period, it is recommended to install it below the lower flange. The migration is -ρ1gh, where ρ1 is the density of the capillary filling fluid ； The range is from -ρ1gh to (-ρ1gh + range)
This post was last edited by 1111111 on 2018-5-14 at 19:49. The height difference h between the two flange-shaped faces – you probably don’t have the ability to determine that accurately. The density ρ1 of the oil in the capillaries – you also can’t measure that. As for the acceleration due to gravity g, you certainly can’t figure it out. The formula is meant to help you understand the principles behind migration, not to allow you to carry out meaningless calculations... Do you get it? What value does the differential pressure gauge show when the tank is empty? Remember this value – it is the deviation-free migration value! . . . This value is 10,000 times more accurate than the value calculated by Hu Qiu.
There’s no need for such professionalism; in a double-flange level gauge, the high-pressure side is at the bottom and the low-pressure side is at the top. After installation, just adjust the zero point. As for migration, it means that the entire range moves along a straight line; the linear relationship remains unchanged, but the zero point changes. I hope this is clear