GTI GTI135/GTI145 Digital Differential Pressure Switch

Overview

The GTI GTI135 and GTI145 Digital Differential Pressure Switches are compact, high-stability micro-differential pressure instruments engineered for precise, real-time monitoring and control of low-pressure differentials in clean, dry, non-corrosive gas streams—primarily air and nitrogen. Based on a miniaturized silicon piezoresistive sensing element, these devices convert minute pressure differences into highly repeatable electrical signals using digital signal conditioning and temperature-compensated analog-to-digital conversion. Unlike analog-only gauges, the GTI135/145 integrates dual independent switching outputs with configurable logic (NPN or PNP open-collector), analog transmission (4–20 mA or 1–5 VDC), and on-device digital processing—including zero-point adjustment, peak/valley hold, digital filtering, and key lock functionality. Designed for embedded integration and panel mounting in space-constrained environments, they meet fundamental requirements for reliability, electromagnetic compatibility (IEC 61326-1), and functional safety in non-hazardous industrial zones.

Key Features

• Two model variants optimized for distinct differential pressure ranges: GTI135 (0–50 Pa to 0–5 kPa) and GTI145 (0–100 Pa to 0–5 kPa), each calibrated per IEC 61298-2 guidelines for pressure transmitters.
• High-resolution segment LCD display with 4-digit readability; selectable units (Pa or kPa) and configurable decimal point positioning for optimal field interpretation.
• Dual independent switch outputs (OUT1 & OUT2), individually programmable as NPN or PNP open-collector types, rated for ≤100 mA load current and ≤30 VDC blocking voltage.
• Analog output compliant with standard industrial protocols: 4–20 mA (2-wire, loop-powered) or 1–5 VDC (3-wire, isolated), both factory-configurable and optionally available with HART® compatibility upon request.
• Onboard digital signal processing includes user-adjustable moving average filter (0.2 s / 1 s / 2 s / 4 s), zero-point calibration via front-panel button, and peak/valley memory retention for transient event analysis.
• Robust mechanical design: PC/ABS housing (UL94 V-0 rated), M5 internal thread + φ3.5 mm barbed fitting interface, IP40 ingress protection, and Class II pollution degree compliance per IEC 60664-2.

Sample Compatibility & Compliance

The GTI135/145 is validated for use with clean, dry, non-aggressive gases—specifically ambient air, medical-grade nitrogen, and instrument air meeting ISO 8573-1 Class 4 or better. It is not suitable for liquids, corrosive vapors (e.g., Cl₂, NH₃, H₂S), or particulate-laden streams without upstream filtration. The device conforms to electromagnetic compatibility standards IEC 61326-1 (industrial environment) and basic safety requirements per IEC 61010-1. While not intrinsically safe or ATEX-certified, its low-power operation (≤30 mA @ 24 VDC) and absence of high-energy circuits permit deployment in Zone 2/Class I Division 2 areas when installed per local electrical codes. For regulated life science applications, the unit supports audit-ready configuration logs when integrated with external SCADA or DCS systems adhering to FDA 21 CFR Part 11 data integrity principles.

Software & Data Management

These switches operate autonomously without host software; all configuration is performed locally via tactile membrane buttons. However, analog output signals are fully compatible with third-party PLCs (e.g., Siemens S7, Allen-Bradley ControlLogix), DCS platforms (Emerson DeltaV, Honeywell Experion), and data acquisition systems (NI CompactDAQ, Keysight DAQ970A). When connected to a controller with trending capability, the 4–20 mA signal enables continuous logging of differential pressure trends—critical for HVAC filter monitoring, cleanroom pressure cascade validation, and biosafety cabinet inflow velocity verification per ISO 14644-3 and NSF/ANSI 49. Optional firmware updates (via USB-to-serial adapter and proprietary utility) support future protocol extensions including Modbus RTU over RS-485.

Applications

• Building automation: Monitoring HVAC duct static pressure, VAV box differential pressure, and filter clogging status in commercial and institutional facilities.
• Pharmaceutical manufacturing: Verifying pressure differentials across HEPA filters in Grade A/B cleanrooms and isolator transfer hatches per EU GMP Annex 1.
• Biosafety and containment: Real-time feedback for negative pressure maintenance in BSL-2/3 laboratories, mobile negative-pressure isolation units, and laminar flow cabinets.
• Industrial process control: Combustion air/fuel ratio balancing in low-pressure burners, furnace draft monitoring, and orifice plate-based flow verification.
• Electronics manufacturing: Clean dry air (CDA) line pressure drop detection and mini-environment chamber differential pressure stabilization.

FAQ

What gases are compatible with the GTI135/145?
Only clean, dry, non-corrosive gases—such as ambient air, nitrogen, argon, and helium—are permitted. Moisture, oil vapor, or acidic/basic gases will degrade sensor performance and void warranty.
Can the analog output be re-ranged in the field?
No—the analog span is fixed at time of manufacture to match the selected differential pressure range. Custom span configurations require factory programming prior to shipment.
Is zero calibration required after installation?
Yes. Due to mechanical stress during mounting and thermal equilibration, a manual zero adjustment is recommended after 30 minutes of powered operation at stable ambient temperature.
Does the device support HART communication?
Standard units do not include HART. However, HART-enabled versions with FSK modulation and Device Description (DD) files are available under OEM agreement.
What is the maximum allowable tubing length for the analog signal?
For 4–20 mA output, total loop resistance must remain ≤500 Ω. With typical 24 AWG copper wire (≈84 Ω/km), maximum one-way distance is ~3 km in ideal conditions—but shielded twisted-pair cable and proper grounding are mandatory beyond 100 m.