IP68 Hydrostatic Level Transmitter for Deep Wells and Storage Tanks

1. Why You Need a Pressure Type Level Transmitter

When a tank is deep, sealed or difficult to access, a simple float or sight gauge no longer provides the continuous, remote signal a modern plant needs. A pressure type (hydrostatic) level transmitter measures the pressure at the bottom of the liquid and converts it directly into level, delivering a 4-20 mA signal that can be monitored from the control room. Because the measurement is based on pressure rather than mechanical floats, it works reliably in deep wells, large storage tanks and sealed vessels, and it is unaffected by foam, turbulence or floating debris that defeat conventional devices.

2. Working Principle of the Pressure Type Level Transmitter

The transmitter senses the hydrostatic pressure generated by the liquid column above the sensor. This pressure equals liquid height multiplied by density and gravity, so a known density yields a direct level reading. The sensor probe — typically stainless steel or titanium alloy — is installed at the bottom or side of the container, and a vented cable references the sensor to atmosphere so only the liquid head is measured. The electronics convert the pressure to a standard 4-20 mA signal powered by 24 V DC, suitable for water, oil and gas applications.

3. Hydrostatic Design Advantages

• Deep-range capability: measures levels from 0 to 200 meters for deep wells and tall tanks.
• IP68 protection: fully sealed against continuous submersion, ideal for permanently immersed service.
• Measurement accuracy: ±1.5% accuracy with stable, repeatable output.
• Corrosion resistance: stainless steel probe withstands water, oil and many process liquids.
• Harsh environment reliability: waterproof, corrosion-resistant cable and sealed construction for outdoor and wet installations.

Common Measurement Challenges & Solutions

Why Choose Our Pressure Type Level Transmitter?

• 0-200 meter measurement range for deep wells and tall tanks
• IP68 ingress protection for permanent submersion
• ±1.5% accuracy with stable, repeatable output
• 4-20 mA output powered by 24 V DC for easy integration
• Stainless steel probe resistant to water, oil and gas
• DN25 flange connection (threaded G1/2, NPT1/2 available)
• Waterproof, corrosion-resistant vented cable
• Unaffected by foam, turbulence and floating debris
• Vertical or horizontal mounting flexibility
• Long service life in harsh, wet environments

Q: What is a pressure type level transmitter?

A pressure type (hydrostatic) level transmitter measures liquid level by sensing the pressure exerted by the liquid column above the sensor. Because hydrostatic pressure is proportional to liquid height and density, the transmitter converts this pressure into a level reading and outputs a standard 4-20 mA signal. This method is robust, has no moving parts, and is widely used in deep wells, storage tanks and sealed vessels where mechanical floats or sight gauges are impractical. It provides continuous, remote level data for control and monitoring systems.

Q: What does IP68 protection mean?

IP68 is an ingress-protection rating indicating the device is dust-tight and protected against continuous immersion in water under conditions specified by the manufacturer. For a level transmitter, this means the probe and cable are fully sealed and can be permanently submerged without water ingress damaging the electronics. This is essential for deep wells, tanks and reservoirs where the sensor remains underwater for its entire service life. Always confirm the depth and duration ratings match your installation.

Q: How does hydrostatic level measurement work?

Hydrostatic level measurement relies on the principle that the pressure at the bottom of a liquid column equals the liquid density multiplied by gravity and liquid height. A submerged sensor measures this pressure, and a vented reference tube cancels atmospheric pressure so only the liquid head contributes to the signal. The transmitter then outputs a 4-20 mA current proportional to level. This technique is reliable, continuous and unaffected by foam or turbulence, making it a standard for tanks and wells.

Q: How deep can this level transmitter measure?

This model supports a measurement range from 0 to 200 meters, covering most deep wells, boreholes and tall storage tanks. The probe is rated for pressures up to 1000 psi, which corresponds to substantial water depth. For very deep applications, the range and cable length should be specified at order time, and the probe is installed at the required reference depth. This deep-range capability makes it suitable for groundwater monitoring and large industrial tanks.

Q: What is the output signal and power supply?

The transmitter provides a 4-20 mA DC analog output, the industry-standard signal for process instrumentation, and is powered by a 24 V DC supply. The two-wire 4-20 mA loop is robust over long distances, making it ideal for remote wells and tanks far from the control room. The signal connects directly to PLC, DCS or SCADA systems, enabling continuous monitoring, alarming and automated pump or valve control.

Q: Can it measure oil and chemical tanks?

Yes. The stainless steel probe is suitable for water, oil and many mild chemical and process liquids. Because measurement depends on hydrostatic pressure, the liquid density must be known to convert pressure into an accurate level reading. For aggressive or strongly corrosive chemicals, confirm material compatibility and consider alternative wetted materials. For oil and fuel tanks, the transmitter provides reliable inventory monitoring without mechanical floats.

Q: What is the difference between gauge and absolute pressure in level measurement?

Gauge pressure is measured relative to atmospheric pressure, while absolute pressure is measured relative to a perfect vacuum. For open tanks and wells exposed to the atmosphere, a vented (gauge-referenced) transmitter is used so atmospheric changes are cancelled and only the liquid head is measured. For sealed or vacuum vessels, absolute or differential references may be needed. Our pressure type transmitter uses a vented reference, making it ideal for open, atmospheric installations like wells and reservoirs.

Q: How is the transmitter installed?

The probe is mounted at the bottom or side of the container, either by threading (G1/2, NPT1/2) or via a DN25 flange for sealed installations. The vented cable is routed to the top and secured, keeping the vent tube open to atmosphere and protected from moisture. The transmitter can be mounted vertically or horizontally as needed. After installation, verify the zero point and configure the range to match the tank or well depth.

Q: Why use a vented cable?

The vented cable contains a small tube that references the sensor's back side to atmospheric pressure. This cancels the effect of changing barometric pressure so the transmitter measures only the hydrostatic pressure of the liquid. Without venting, the reading would drift with weather changes. Keeping the vent tube dry and unobstructed is critical; moisture or blockage in the vent can cause measurement error, so the tube end is typically protected with a breather filter.

Q: What media can it measure?

The transmitter is designed for liquids including water, oil, gas-related process fluids and many mild chemicals. The stainless steel probe and waterproof cable handle wet, outdoor and submerged environments well. The measurement principle works for any liquid whose density is known and stable, since level is derived from hydrostatic pressure. For media with varying density, such as mixed or aerated liquids, additional compensation or a different technology may be required.