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Tech-Tip Reference # : |
TT_33_Level_Sensing |
Date Posted : |
3/13/2007 |
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Signet's 2450 Pressure sensors allow users to measure the level of liquid in a tank (or vessel). The sensor will only measure the level of liquid directly above the sensor. If there is liquid below the sensor (see figures below), it will not be included in the level calculation. There is a parameter called "Sensor Offset" in 8250 Level Transmitters or 8900 Multi-Parameters, which enables users to include the liquid level below the sensor to calculate the total level in a tank. The Sensor Offset must always be referenced to a Zero point on the tank. See the diagrams below. Figure 2 below can actually be thought of as measuring the emptiness of the tank.
NOTE:
• If the 4-20mA version of the 2450 is being used, the Sensor Offset value should be placed in the PLC.
• This tech-tip also applies to 2250 Hydrostatic Level Sensors for submersible applications.
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The vessel contains 10 feet of water, from the drain outlet to the water surface.
The Sensor Offset is -2 feet.
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The vessel can hold an additional 5 feet of water, from the water surface to the zero point.
The Sensor Offset is -15 feet. |
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Figure 1
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Figure 2
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The vessel contains 15 feet of water, from the bottom of the tank to the water surface.
The Sensor Offset is +5 feet.
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The vessel contains 10 ft. of water, from the water surface to the zero point.
The Sensor Offset is zero. |
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Figure 3
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Figure 4
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© 2007 Georg Fischer Signet LLC
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