Fischer DE90 Differential Pressure Transmitter

Overview

The Fischer DE90 Differential Pressure Transmitter is a high-precision, industrial-grade piezoresistive pressure sensing instrument engineered for continuous, stable monitoring of differential pressure in clean air and neutral gas applications. Designed and manufactured by FISCHER Mess- und Regeltechnik GmbH — a German family-owned enterprise headquartered in Bad Salzuflen since 1950 — the DE90 exemplifies decades of expertise in measurement and control engineering. Its core sensing element consists of two matched ceramic pressure sensors, each featuring integrated signal conditioning circuitry that delivers high linearity, low hysteresis, and exceptional long-term repeatability. Unlike mechanical or capacitive alternatives, the DE90’s monolithic ceramic sensor architecture eliminates elastomeric seals and moving parts, ensuring immunity to aging, creep, and media-induced drift. The device operates on a 2-wire 4–20 mA loop powered by 12–36 V DC, supporting seamless integration into building management systems (BMS), HVAC controllers, and PLC-based automation infrastructures. It is explicitly optimized for low-differential-pressure environments — including cleanroom pressure zoning, fume hood containment verification, and HEPA filter integrity monitoring — where resolution down to ±1 Pa and stability over extended calibration intervals are mission-critical.

Key Features

• Piezoresistive ceramic dual-sensor architecture for true differential measurement — no shared reference cavity or internal venting required
• Accuracy of ±0.1 % full scale (FS) at 23 °C, traceable to national standards via factory calibration certificate (optionally accredited to ISO/IEC 17025)
• Long-term zero and span stability better than 0.1 % FS per year — validated under accelerated aging tests per DIN EN 61298-2
• Robust aluminum housing rated IP65, suitable for indoor industrial and laboratory environments with condensation or occasional washdown exposure
• Configurable output: standard 4–20 mA (HART-compatible upon request); optional 0–10 V analog output or digital RS485 Modbus RTU interface (model-dependent)
• Zero and span adjustment via local DIP switches or remote configuration using Fischer’s proprietary PC software suite (compatible with Windows 10/11, USB-to-RS485 adapter required)
• Integrated overpressure protection up to 5× full-scale range — prevents sensor damage during system surges or commissioning errors
• EMC compliance per DIN EN 61326-1 Class A and DIN EN 61000-6-2/6-4 ensures reliable operation in electrically noisy industrial settings

Sample Compatibility & Compliance

The DE90 is certified for use with non-corrosive, non-condensing gases — primarily ambient air, nitrogen, carbon dioxide, and other chemically inert process gases. It is not rated for liquids, steam, or aggressive media such as chlorine, ammonia, or solvents. For cleanroom applications, the transmitter meets functional requirements outlined in ISO 14644-1 (Classification of Air Cleanliness) and EU GMP Annex 1 (2022), particularly regarding differential pressure maintenance between classified zones (e.g., ISO Class 5–8 rooms). While the DE90 itself does not carry formal FDA 21 CFR Part 11 validation out-of-the-box, its firmware supports audit-trail-capable configuration logging when paired with Fischer’s EA15 data logger — enabling compliance-ready documentation for GLP/GMP-regulated facilities. All units ship with a Declaration of Conformity (DoC) and optional factory calibration report (as per DIN EN ISO 9001:2015 procedures).

Software & Data Management

Fischer provides the free *FISCHER ConfigTool* desktop application for Windows OS, enabling full parameterization of the DE90 without hardware modification. Users can configure measurement range, damping time (0–32 s), linearization mode (linear or square-root for flow-derived applications), and output scaling. The tool also supports firmware updates and diagnostic readouts (e.g., sensor health status, supply voltage, internal temperature). When integrated with the EA15 universal indicator/logger, the DE90 feeds real-time pressure data into timestamped CSV or PDF reports, with configurable alarm thresholds and event-triggered logging. All logged datasets include metadata (operator ID, calibration due date, sensor serial number), satisfying traceability requirements under ISO/IEC 17025 and pharmaceutical quality systems. No cloud dependency: data remains on-premise unless explicitly exported.

Applications

• Cleanroom environmental monitoring — maintaining prescribed pressure differentials (e.g., +15 Pa from corridor to ISO Class 7 room) per ISO 14644-3
• HEPA/ULPA filter monitoring — detecting progressive clogging via rising ΔP across filter banks in pharmaceutical isolators and biosafety cabinets
• Fume hood face velocity assurance — verifying negative pressure gradients relative to lab ambient for operator safety (ANSI/AIHA Z9.5 compliance)
• Building envelope integrity testing — quantifying air leakage rates during blower door tests (ASTM E779, ISO 9972)
• Ventilation system balancing — validating airflow distribution across duct branches using pitot tube or orifice plate interfaces
• OEM integration in medical gas panels, semiconductor tool exhaust systems, and HVAC control modules requiring compact, stable DP feedback

FAQ

Is the DE90 suitable for measuring liquid pressure?
No. The DE90 is designed exclusively for gaseous media. Liquid ingress will damage the ceramic sensor elements and void warranty.
Can the DE90 be calibrated in-field without specialized equipment?
Yes — zero calibration is possible via the front-panel button under atmospheric conditions; however, full span calibration requires a traceable pressure standard and is recommended annually or per ISO/IEC 17025-defined intervals.
Does the DE90 support HART communication?
Standard DE90 units feature analog-only 4–20 mA output. HART-enabled variants (DE90-H) are available upon request with additional firmware and terminal configuration.
What is the minimum measurable differential pressure?
The base model supports ranges as low as ±25 Pa. Custom low-range configurations (±5 Pa) are available for ultra-sensitive cleanroom zoning applications.
Is explosion-proof certification available for the DE90?
The DE90 itself is not ATEX-certified. For hazardous area use, Fischer recommends the DE43 (ATEX II 3G Ex nA IIC T4 Ga) or DS21 (functional safety-rated per DIN EN 61508 SIL2) as alternatives.