CST305X-DPT Differential Pressure Transmitter

Pressure measurement

The CST305X-DPT is a digital, intelligent differential pressure transmitter developed by CST Instruments for the continuous measurement of differential pressure, flow, and liquid level in industrial process applications. It combines a proven capacitive silicon sensor with a high-performance microcontroller and ASIC signal-conditioning circuitry, giving excellent long-term stability, high accuracy, and ease of on-site configuration. The transmitter is suitable for use across the European process industry, including food and beverage, chemical, water treatment, power generation, and oil and gas. A gauge-pressure version of the same platform, the CST305X-GPT, is also available — see CST305X Gauge Pressure Transmitter.

Advantage

  • Capacitive or piezoresistive silicon sensing element with a fully sealed, isolated diaphragm assembly.
  • 18-bit A/D conversion for excellent resolution and measurement stability.
  • Integrated ASIC handles signal acquisition, linearisation, and current output for excellent vibration resistance and unit-to-unit interchangeability.
  • On-site zero and span adjustment via push-buttons — no external pressure standard required.
  • Optional local LCD display with three-button menu for full parameter configuration (engineering unit, range, damping, output type, and more).
  • Rotatable electronics housing (±90°) for optimised cable entry orientation and display readability.
  • Robust stainless steel process flange and metal housing for long service life in demanding process environments.
  • Intrinsically safe (Ex ia) and flameproof (Ex d) versions available for hazardous-area installations.

Technical Features

ParameterSpecification
Measuring range0–1.5 kPa up to 0–20,680 kPa (multiple range codes available)
Output signal4–20 mA with HART® protocol; linear or square-root (extraction) output
Power supplyTwo-wire, loop-powered
Diaphragm materialStainless steel 316L or Hastelloy C
Fill fluidSilicone oil or fluorinated oil
Process connection¼” NPT female (three-valve/five-valve manifold and waist-flange adaptor options available)
Maximum static pressure14 MPa / 25 MPa / 32 MPa, depending on configuration
Wetted O-ring materialBuna-N (NBR), Viton® (FKM), or low-temperature Viton® (FKM-GFLT)
Cable entryM20 × 1.5
Local indicationOptional LCD display showing measured value, output percentage, loop current, and sensor temperature
Mounting2″ (DN50) pipe-mount or wall/panel bracket (carbon steel or stainless steel)

Exact accuracy class, protection rating, and approval markings vary by configuration and are confirmed by the nameplate and EU Declaration of Conformity / EU-Type Examination Certificate supplied with each unit.

EU Compliance & Hazardous-Area Certification

Certified hazardous-area variants of the CST305X-DPT are designed for use in potentially explosive atmospheres in accordance with Directive 2014/34/EU (ATEX), with technical requirements demonstrated against the IEC/EN 60079 series of standards (EN IEC 60079-0, EN 60079-11 for intrinsic safety “i”, EN 60079-1 for flameproof enclosures “d”):

  • Intrinsically safe (Ex ia IIC T4–T6): for use with a certified safety barrier or isolator located in the safe area.
  • Flameproof (Ex d IIC T4–T6): certified flameproof enclosure for direct installation in the hazardous area.

The specific protection concept, equipment group and category, temperature class, and all associated electrical safety parameters (Ui, Ii, Pi, etc.) applicable to a given unit are defined solely by that unit’s nameplate and its EU-Type Examination Certificate / EU Declaration of Conformity, which take precedence over any general figures quoted here.

Applications

  • Liquid, gas, and steam flow measurement
  • Open and closed vessel level measurement (dry-leg and wet-leg installations)
  • Process control systems
  • Petroleum and chemical industry
  • Power generation and water treatment

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