Teledyne 4220 Submerged Probe Nose Sections, Solids, Minimum Reliable Detection Level

4220 Flow Meter

Section 4 Submerged Probe Installation

The probe has several ports through which liquid enters the body to contact the pressure transducer. The only way for the probe to malfunction is for all the ports to be completely blocked. Most substances likely to cover the probe are somewhat porous, which still allows the hydrostatic pressure of the flow stream over the probe to reach the transducer.

4.1.1Functionality Under Consequently, the probe will normally continue to function even

Solids	when covered with several inches of silt or sand. Note however,
	that porous solids, such as wood chips or other organic material
	that may swell considerably when soaked in water, can interfere
	with the correct operation of the pressure transducer. In extreme
	cases, swelling material can put enough pressure on the dia-
	phragm of the pressure transducer to deform it. This will ruin
	the submerged probe by introducing a permanent offset to the
	pressure transducer.

4.1.2Minimum Reliable Detection Level

4.2Submerged Probe Nose Sections

Standard Nose

Section

Note

Always install the probe where it will be under water, even if only an inch or so. The probe cannot measure levels that fall below its location in the stream.

It is important to note that there is a practical minimum water level below which the submerged probe cannot reliably measure level. This minimum level is approximately equal to the height of the probe body, 0.1 ft. (1.3 in. or 0.030 m).

Liquid levels lower than this will be below the levels used to cali- brate the sensor. The submerged probe level sensor will continue to measure levels less than 0.1 ft.; however, the accuracy of the measurement in this range is not guaranteed. Consequently, you should always use the submerged probe with caution in very low flow situations.

Teledyne Isco provides three nose sections, each designed for spe- cific flow stream conditions.

A complete list of nose sections and their part numbers can be found in Appendix B.

Standard Nose Section – The standard nose section works in any flow stream and will be installed on your probe unless oth- erwise specified in your order. It is particularly well suited for flow streams with high velocities because its shape overcomes hydraulic problems that develop in these flow streams. At veloc- ities exceeding 5 feet per second (1.5 meters per second), localized low-pressure areas form near the submerged probe, which can result in erroneous level readings. The length of the nose section (3.87 inches or 9.84 cm) minimizes low-pressure areas by allowing the flow stream to stabilize before it reaches the probe’s entrance ports.

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