Cole-Parmer® Model 32935-40 Low-Pressure-Drop Gas Mass Flow Meter and Controller

Overview

The Cole-Parmer® Model 32935-40 is a precision-engineered gas mass flow meter and controller based on laminar flow differential pressure (DP) measurement technology. Unlike thermal-based or orifice-type meters, this instrument employs a micro-machined laminar flow element (LFE) to generate a linear, repeatable pressure differential proportional to volumetric flow—then converts it to true mass flow using real-time temperature and pressure compensation. Its defining engineering feature is an exceptionally low full-scale pressure drop ranging from 0.1 to 0.69 psid, minimizing system backpressure and enabling integration into sensitive gas delivery systems, vacuum-compatible sampling trains, and low-headroom analytical setups. With no warm-up time required and sub-10-ms dynamic response in metering mode, the device supports rapid transient flow monitoring and closed-loop control in applications where pressure stability and signal fidelity are critical.

Key Features

• Laminar flow element architecture ensures high linearity (<±0.5% of reading), long-term stability, and immunity to upstream turbulence—eliminating the need for extensive straight-pipe runs.
• Real-time gas selection from a library of 98 NIST-traceable standard gases—including air, N₂, O₂, CO₂, CH₄, Ar, He, H₂, and common industrial blends—with automatic property compensation (viscosity, specific heat, molecular weight).
• Simultaneous four-parameter display on a high-contrast color TFT screen: instantaneous mass flow rate, absolute line pressure, fluid temperature, and (for controller variants) setpoint value—with intuitive color-coded over-range indication (yellow ≤100%, red up to 128%).
• Integrated rechargeable lithium-ion battery enables portable field verification and on-site calibration without external power—ideal for HVAC commissioning, emissions stack audits, and mobile lab deployments.
• Single multi-pin connector consolidates power input (120/230 VAC or battery), analog output (0–5 VDC), and RS-232 communication—reducing wiring complexity and improving EMI resilience in industrial control cabinets.
• Factory-provided NIST-traceable calibration certificate includes uncertainty budgets per ISO/IEC 17025 guidelines, supporting compliance with internal quality procedures and regulatory documentation requirements.

Sample Compatibility & Compliance

The Model 32935-40 is validated for use with non-corrosive, particle-free gases across ambient temperatures (5–45°C) and pressures up to 150 psia. It meets material compatibility standards for stainless steel 316 wetted parts and fluoropolymer seals (e.g., Kalrez®), ensuring suitability for ultra-high-purity (UHP) semiconductor process gases and medical-grade oxygen/nitrogen streams. While not certified to ATEX or IECEx for hazardous locations, its low-energy design and intrinsic safety profile make it appropriate for Class 1, Division 2 environments when installed per NEC Article 500. The device supports Good Laboratory Practice (GLP) and Good Manufacturing Practice (GMP)-aligned workflows through deterministic analog output, immutable calibration records, and absence of firmware-dependent digital protocols that may complicate 21 CFR Part 11 validation.

Software & Data Management

Operation is fully local—no proprietary software or driver installation is required. All configuration—including gas selection, units (sccm, slm, kg/h), zero/span adjustment, and alarm thresholds—is performed via the integrated membrane keypad surrounding the TFT display. The 0–5 VDC analog output provides direct interface with PLCs, SCADA systems, chart recorders, or PID controllers without signal conditioning. For archival purposes, users may log output signals using third-party DAQ hardware; the device itself does not store historical data or support USB/SD export. This architecture prioritizes determinism, electromagnetic robustness, and operational transparency—key attributes for regulated environments where software validation overhead must be minimized.

Applications

• Air quality monitoring stations requiring stable, low-drift flow control during particulate or VOC sampling.
• Natural gas custody transfer verification and field meter calibration against reference standards.
• Gas chromatography carrier gas regulation and detector flow optimization.
• In-line verification of mass flow in pharmaceutical lyophilization and inert gas purging systems.
• Educational laboratories demonstrating compressible flow behavior, gas property effects, and feedback control dynamics.
• Environmental emission testing where low-pressure-drop sampling preserves sample integrity across filter and analyzer trains.

FAQ

Does this device require periodic recalibration?
Yes—while the laminar flow element exhibits excellent long-term stability, Cole-Parmer recommends annual recalibration against NIST-traceable standards to maintain stated accuracy, especially in regulated applications.
Can it measure gas mixtures not in the built-in library?
No—only the 98 preloaded gases are supported. Custom gas mixtures require external compensation or third-party flow modeling tools.
Is the 0–5 VDC output isolated?
Yes—the analog output is galvanically isolated to prevent ground loops and ensure compatibility with grounded instrumentation systems.
What is the maximum allowable operating pressure?
150 psia (10.3 bar) at ambient temperature; derating applies above 45°C per manufacturer’s pressure-temperature rating curve.
Can the battery be replaced in the field?
No—the integrated lithium-ion battery is sealed and service-replaceable only by authorized Cole-Parmer technical centers to preserve IP rating and calibration integrity.