The KOBOLD KPW is a submersible pressure transducer that converts the hydrostatic pressure of the liquid column above it into a continuous electrical level signal, delivering reliable level measurement for tanks, wells, and water systems where accuracy and durability are essential. Its IP68-rated design allows complete immersion while maintaining measurement integrity, making it suitable for both permanent installations and portable monitoring setups.
Designed for industrial tank level monitoring, irrigation control systems, water and wastewater treatment facilities, and well head measurement, the KPW provides continuous level data in challenging environments like clarifier level control and wet well monitoring to groundwater monitoring, aquifer studies, and municipal water supply management.
How Does a Submersible Pressure Transducer Measure Level?
A submersible pressure transducer measures level by detecting the hydrostatic pressure created by the liquid column above the sensor. Installed at or near the bottom of a tank or well, the KPW converts the pressure exerted by the liquid height into a proportional electrical signal, independent of tank shape or volume.
For water level applications, the reading converts directly to depth: approximately 2.31 feet of water column equals 1 PSI, enabling simple programming in control systems and SCADA interfaces. The KPW includes a vented cable that compensates for atmospheric pressure changes, ensuring accurate readings in open tanks and outdoor installations regardless of barometric variations.
What Accuracy Does the KPW Provide?
The KPW uses advanced semiconductor and thin-film sensing technology to deliver a standard accuracy of ±0.25% of full scale (BFSL), with an optional ±0.125% of full scale specification available for ranges of 5 PSI and above, according to specifications. Response time is less than 1 millisecond (10–90% of full scale).
The optional ±0.125% specification positions the KPW among the most precise submersible transmitters available for demanding level monitoring installations, and the fast response enables tracking of rapid level changes in pump control and process monitoring. Long-term stability is less than ±0.2% of full scale per year, non-accumulating, and temperature compensation from 32 to 122°F (0 to 50°C) is designed to minimize thermal drift in zero and span readings.
Rugged 316 Stainless Steel Construction
The KPW is built with a 316 stainless steel housing and connection and a polyamide nose cone as standard, with an optional 316 stainless steel weighted nose cone for flow streams or installations requiring extra weight. The submersible cable is polyurethane as standard, with water-blocked PVC or FEP options for specific chemical compatibility requirements.
High overpressure protection, proof pressure of 2X range and burst pressure of 4X range, helps prevent sensor damage from installation errors and system surges. With a service life exceeding 100,000,000 load cycles, the KPW demonstrates long-term stability for continuous monitoring where sensor replacement is costly and disruptive.
What Output Signals and Input Power Does the KPW Use?
The standard output is a 4-20 mA two-wire signal compatible with most PLCs and control systems, supporting transmission over extended cable distances without degradation.
Unregulated input power of 10-30 VDC supplies the 4-20 mA and 0-5 VDC outputs, with 14-30 VDC for the 0-10 VDC output and 5-30 VDC for the 0.5-2.5 VDC output, simplifying installation in existing systems. Built-in reverse polarity and short circuit protection helps prevent damage during installation and commissioning, reducing field service calls.
Pressure Ranges from Shallow Sumps to Deep Wells
The KPW is available in ranges from 0–50 inches of water column up to 0–1,000 PSIG, covering shallow sumps through deep well applications. This selection allows precise matching to each installation, optimizing accuracy and resolution; the 0–500, 0–750, and 0–1,000 PSIG ranges are offered with the 4-20 mA output, per the ordering specifications.
Installation Options and Accessories
The KPW ships with a standard polyamide nose cone suitable for most water-based applications, and a G ½ male threaded connection provides secure mounting. An optional adapter with ¼" NPT female thread enables direct threaded installation into tank fittings, and any cable length can be specified in feet at time of order.
Accessories enhance installation versatility: cable clamps secure the submersible cable in turbulent conditions, desiccant cartridges protect the vent tube from moisture in humid environments, and filter elements help keep particulates away from the sensing diaphragm in applications with suspended solids or debris.
CE Compliance and Environmental Protection
The KPW is CE compliant to EMC Norm EN 61326:1997/A1:1998, providing RFI, EMI, and ESD protection for reliable operation near variable frequency drives, motor starters, and other sources of electromagnetic interference. Environmental protection is rated IP68 for continuous submersion, according to specifications.
Shock resistance of 100g per IEC 60068-2-27 and vibration resistance of 15g per IEC 60068-2-6 support installation on pump skids and mobile equipment where mechanical stress could affect less robust sensors.
Common Questions about KPW - Submersible Pressure Transducer
The KPW covers ranges from 0–50 inches of water column up to 0–1,000 PSIG, spanning shallow sump measurement through deep well applications. Intermediate ranges include 100, 150, 200, and 400 inH2O plus 2 through 350 PSIG steps, so the range can be matched closely to the actual level span, according to specifications.
Standard accuracy is ±0.25% of full scale (BFSL), including non-linearity, hysteresis, non-repeatability, and zero and full scale errors. An optional ±0.125% of full scale version is available on ranges of 5 PSI and above. Stability is better than ±0.2% of full scale per year, non-accumulating, according to specifications.
A 4-20 mA two-wire current output is standard. Three-wire voltage versions are offered with 0-5 VDC, 0-10 VDC, or 0.5-2.5 VDC signals. The highest ranges (0–500, 0–750, and 0–1,000 PSIG) are available with the 4-20 mA output, according to the ordering specifications.
The 4-20 mA and 0-5 VDC versions accept 10-30 VDC, the 0-10 VDC version accepts 14-30 VDC, and the 0.5-2.5 VDC version accepts 5-30 VDC. Power may be unregulated, and the electronics include reverse polarity and short circuit protection to help prevent wiring damage during commissioning.
The submersible cable contains a vent tube that references the sensor to atmospheric pressure, so barometric changes do not shift the level reading. An optional desiccant cartridge protects the vent tube from moisture ingress in humid environments, helping preserve accuracy in open tanks and outdoor installations, according to specifications.
Polyurethane (PUR) cable is standard. Optional water-blocked PVC cable is available for ranges of 200 PSI and above, and FEP cable is offered for chemical compatibility requirements. Any cable length can be ordered, the exact length in feet is simply inserted into the part number, according to specifications.
The compensated range is 32 to 122°F (0 to 50°C), media temperature is 14 to 122°F (-10 to 50°C), and storage temperature is -22 to 175°F (-30 to 79°C), according to specifications. Within the compensated range, the design is intended to minimize thermal drift of zero and span.
The transducer is rated IP68 for continuous submersion and is CE compliant to EMC Norm EN 61326:1997/A1:1998 with RFI, EMI, and ESD protection. Mechanical ratings include 100g shock per IEC 60068-2-27 and 15g vibration per IEC 60068-2-6, according to specifications.
For water, approximately 2.31 feet of water column equals 1 PSI, so depth is calculated by multiplying the pressure reading in PSI by 2.31. This hydrostatic relationship depends only on liquid depth and density (not tank shape or volume) which keeps level programming in PLCs and SCADA systems simple.
No routine maintenance is required, according to the manual. Recalibration frequency depends on the user's quality assurance program; where none exists, KOBOLD recommends a one-year cycle. Zero and span are field-adjustable by ±10% of full scale using the internal potentiometers with a suitable pressure source and meter.