Submersible Pressure Transducer

Submersible pressure transducer is a liquid level measurement equipment based on hydrostatic pressure measurement principle, which is widely used in industrial, municipal, water conservancy and other fields of wave body liquid level monitoring. The following is an introduction of its basic knowledge in terms of working principle, structural composition, core features and application scenarios.

The working principle of submersible pressure transducer 

The core principle of submersible pressure transducer is the positive proportionality between liquid static pressure and liquid level height: 

The static pressure of a point in the liquid is equal to the product of the liquid density (p), the acceleration of gravity (g) and the vertical height of the point to the liquid surface ( h), i.e. P= pgh. Sensor probe into the liquid, through the measurement of the liquid static pressure on the probe, combined with the liquid density and gravitational acceleration (usually a constant), you can calculate the height of the liquid level (h = P / (pg)) 

mainly consists of the following parts: 

Pressure-sensitive element (probe): directly in contact with the liquid being measured, the perception of the static pressure of the liquid, the common material has stainless steel ( 316L, corrosion-resistant), ceramic (high precision), titanium alloy (strong corrosive environment) and so on.

Ventilation cable / guide rod: used to balance the atmospheric pressure above the probe (to eliminate the impact of air pressure on the measurement above the liquid surface), to ensure that the measurement is pure liquid static pressure.

Signal processing unit: convert the pressure signal into standard electrical signal (such as 4-20mA, RS485, etc.), part of the model integrated display, can directly display the liquid level value.

Mounting accessories: such as fixing flanges, brackets, etc., used to fix the device on the top or side of the container.

Features of submersible pressure transducer 

1. Stable measurement, high accuracy 

Static measurement error is usually ±0.2%~±0.5% FS (full scale), some high-precision models up to ±0.1% FS, suitable for high stability requirements of the scenario (such as water tanks, storage tanks) without the influence of fluctuations in the liquid level, bubbles, steam, etc. (due to measurement of static pressure, non-contact with the liquid level). The probe is not in contact with the liquid surface).

2. Simple structure, convenient installation 

The probe can be directly put into the liquid, without complex debugging, especially suitable for deep liquid level (such as deep wells, pools) or closed containers (such as pressure tanks) 

Flexible adjustment of the measurement range through the length of the cable, the range is usually from 0~10m to 0~200m, and some models can be even deeper 

3. Adaptability 

Suitable for a wide range of liquid media: water, sewage, oil, acid and alkali solutions (need to be matched with the corresponding corrosion-resistant material probe). Corrosion-resistant material probe), etc..

Withstand a certain temperature (-40 ℃ ℃ ~ 150 ℃, special models can be higher) and pressure (depending on the probe pressure rating) 

moderate cost, easy maintenance 

4. Compared with radar, ultrasonic and other non-contact instrumentation, the cost is lower, suitable for large-scale applications (such as municipal water supply systems) no wearing parts, routine maintenance only need to regularly check the cable sealing (to prevent water ingress) and the cleanliness of the probe.

Limitations of submersible pressure transducer 

Affected by the density of the medium: If the density of the liquid is not stable (such as mixed liquids, temperature changes lead to density fluctuations), it will directly affect the measurement accuracy, and need to be corrected by additional means (such as temperature compensation) 

Afraid of clogging and abrasion: If the probe is in contact with high-viscosity media (such as slurry) or a large number of impurities in the liquid, it may be due to clogging, loss of signal drift, and need to be cleaned periodically. Fear of clogging and wear: If the probe comes into contact with high viscosity media (e.g. slurry) or liquids containing large amounts of impurities, it may drift due to clogging, wear and tear.

Installation restrictions: direct contact with the liquid, not applicable to food and medicine and other very high hygiene requirements (to avoid contamination) or easy to crystallize, easy to solidify the medium (may wrap the probe).

Application Scenarios of submersible pressure transducer 

1.Water treatment industry 

Pool/tank level monitoring:Water storage tanks and clear pool level measurement in water treatment plants and sewage treatment plants.

Nullah flow calculation: with the flow formula, through the level difference to calculate the water flow in the channel (need to be combined with the shape of the channel parameters).

2. Petrochemical tank level measurement: monitor the real-time level of gasoline, diesel, chemical raw material storage tanks, support explosion-proof type for hazardous areas. Reactor level control: linked with the control system to achieve automatic liquid level adjustment (such as feed, discharge control).

3. Environmental protection and water conservancy 

River and lake water level monitoring: direct installation, for hydrological stations, reservoirs, real-time water level monitoring sewage pumping station level control: through the level signal to automatically start and stop the drainage pumps, to avoid overflow or operation.

4.Agriculture and Construction 

Agricultural irrigation pool:Monitor the reservoir level to realize water-saving irrigation automation.

High-rise building water tank: Measure the level of water tank on the roof of the building, linkage water supply pump to realize constant pressure water supply.

5. Food and medicine 

Tank level monitoring: milk, medicine and other food and medicine level media level measurement, probe material must meet the health standards (such as 316L stainless steel + food grade seals).

Submersible pressure transducer with its cost-effective, easy to install and strong adaptability, become one of the mainstream choice of industrial level measurement, underground pools and other scenes. Selection needs to pay attention to the medium corrosive, installation environment and signal need to be especially suitable for open container, request, if necessary, with the display instrument or host computer system to achieve data visualization and automation control. For high temperature, high viscosity or complex conditions, can consider ultrasonic, radar and other types of liquid level meter as a supplement.