Groundwater level, temperature and conductivity (CTD) Sensors

KELLER Series 36XW-CTD

The Series 36XW-CTD by KELLER Pressure is a high-precision, multi-parameter probe engineered to monitor key water quality metrics—conductivity, temperature, and depth (pressure)—in environmental and hydrological applications.

Core Capabilities

• Multi-parameter sensing: Combines measurements of conductivity, temperature, and hydrostatic pressure (depth) in one compact probe

• Superior precision:

  • Pressure accuracy: ±0.05 % of full scale; total error band within ±0.1 % over 0–50 °C

  • Temperature accuracy: ±0.1 °C with integrated Pt1000 sensor (resolution ≤0.01 °C)

  • Conductivity accuracy: ±2.5 % of the selected range (0.2 / 2 / 20 / 200 mS/cm)

Digital Interfaces & Connectivity

• RS-485 interface: Supports Modbus RTU and KELLER’s proprietary bus protocol; capable of communication over distances up to ~1.4 km; compatible with CCS30 software for configuration and data logging

• Optional SDI-12 interface (specifically in XiW-CTD variant): Optimized for battery-powered, multi-sensor networks and environmental logging; energy-efficient standby (< 0.1 mA)

Mechanical & Environmental Design

• Construction: Robust stainless-steel housing (with options for titanium or Hastelloy for high-chemical compatibility)

• Compact form factor: Diameter Ø22 mm; length approximately 240 mm—suitable for insertion into 1-inch sounding tubes and wells

• Operational durability:

  • Vibration resistance: 10 g across 10–2000 Hz.

  • Shock resistance: up to 50 g.

  • Ingress protection: IP68-rated for submersion

• Extended lightning/surge protection: Available as a standard or optional feature depending on interface configuration

Performance & Stability

• Long-term stability: ≤ ± 0.1 % full scale per year under reference conditions; annual recalibration is recommended

• High measurement fidelity:

  • Pressure resolution: 0.0005 % FS.

  • Signal stability: 0.0025 % FS (noise-free)

• Conductivity resolution: ≤ 0.05 %; compensation for temperature dependencies per EN27888

Applications & Software Ecosystem

• Ideal for: Water quality monitoring, salt/salinity level detection, groundwater and surface water assessment, hydrostatic depth measurements, and utility/potable water assessments.

• Software support:

  • CCS30: For configuration, live data visualization, measurement logging (up to 100 values/sec), and export functions

• Calibration tools: Conductivity Calibration Tool available to adapt the conductivity sensor for specific mediums, used via RS-485