Michell EA2, DMT143 & DMT152 Industrial Dew Point Transmitters

Overview

The Michell EA2, DMT143, and DMT152 dew point transmitters are precision-engineered instruments designed for continuous, real-time measurement of moisture in industrial gases across demanding laboratory, pharmaceutical, semiconductor, and energy applications. Each model employs a distinct but rigorously validated sensing principle: the EA2 utilizes Michell’s proprietary ceramic aluminum oxide (Al₂O₃) sensor operating on the principle of capacitance change induced by water vapor adsorption; the DMT143 and DMT152 integrate Vaisala’s DRYCAP® polymer capacitive technology—featuring integrated temperature compensation and automatic dry-end calibration—to deliver stable, low-drift performance over extended intervals. All three models conform to fundamental thermodynamic definitions of dew point temperature (°Cdp), defined as the temperature at which a given gas sample reaches water vapor saturation under constant pressure. This physical parameter is directly traceable to the International Temperature Scale (ITS-90) and serves as the primary metric for specifying moisture contamination limits in compressed air (ISO 8573-1), medical gases (ISO 8573-3, EN ISO 8573-7), natural gas (ISO 12213-2), and inert process atmospheres.

Key Features

• High-reliability sensor architecture: EA2 features a robust, corrosion-resistant 316 stainless steel sampling module with hermetically sealed alumina sensor; DMT143/DMT152 utilize encapsulated DRYCAP® polymer elements with anti-condensation heating (DMT143) or passive cold-trap design (DMT152) for sub-zero operation.
• Wide operational range: EA2 covers −110 to +20 °Cdp; DMT143 spans −70 to +60 °Cdp; DMT152 extends to ultra-low levels of −80 to −20 °Cdp—enabling quantification of moisture down to single-digit ppm_v in nitrogen, argon, hydrogen, and SF₆.
• Compliance-ready outputs: Standard 4–20 mA analog output with HART option (EA2); configurable voltage (0–10 V) or current (4–20 mA) plus RS-485 Modbus RTU digital interface (DMT143/DMT152) for integration into SCADA, DCS, and MES platforms.
• Hazardous area certification: EA2 carries IECEx, ATEX, UKCA, and cQPSus approvals for Zone 0/1 (gas) and Zone 20/21 (dust); DMT143/DMT152 are rated for Zone 2/22 environments.
• Calibration integrity: Factory-supplied NPL- or NIST-traceable calibration certificates included; DMT143 supports two-year calibration intervals per manufacturer recommendation; EA2 and DMT152 recommend annual verification under GLP/GMP conditions.

Sample Compatibility & Compliance

These transmitters are validated for use with non-aggressive, non-condensing process gases including compressed air (oil-free and lubricated), medical oxygen and nitrous oxide (per ISO 8573-7), CNG and LNG carrier streams, nitrogen blanketing systems, and inert purge gases in gloveboxes (KF40 flange option). They are not suitable for direct measurement in corrosive or solvent-laden streams (e.g., chlorine, ammonia, acetone vapor) without appropriate pre-conditioning. All models comply with electromagnetic compatibility standards (EN 61326-1), RoHS Directive 2011/65/EU, and support audit requirements under FDA 21 CFR Part 11 when paired with compliant data acquisition software (e.g., Vaisala Insight PC with electronic signature and audit trail enabled). The EA2’s intrinsic safety design meets IEC 60079-11 for use in explosive atmospheres without additional barriers.

Software & Data Management

The DMT143 and DMT152 are fully compatible with Vaisala Insight PC software (v3.0+), enabling configuration, real-time monitoring, data logging (CSV export), alarm threshold setting, and firmware updates via USB-to-RS485 adapter. Insight supports 21 CFR Part 11-compliant user access control, electronic signatures, and immutable audit trails when deployed on validated Windows OS platforms. The EA2 supports configuration via handheld HART communicator or Modbus-enabled host systems. All models generate time-stamped output signals suitable for integration into LIMS or ELN systems where raw dew point values (°Cdp) and calculated ppm_v equivalents are required for QC release documentation.

Applications

• Pharmaceutical manufacturing: Monitoring dew point in cleanroom nitrogen purges, lyophilizer chamber backfill, and sterile compressed air systems (ISO 8573-1 Class 2 or better).
• Semiconductor fabrication: Controlling moisture in bulk gas delivery lines (N₂, Ar, He) where <1 ppb H₂O is critical for photolithography and ALD/CVD processes.
• Energy infrastructure: Verifying dryness of SF₆ insulation gas in high-voltage switchgear per IEC 60480 and ASTM D2029.
• Research laboratories: Quantifying trace moisture in cryogenic gas studies, fuel cell feed gas characterization, and catalyst deactivation experiments.
• Industrial gas production: Final quality verification of liquid nitrogen, argon, and oxygen prior to cylinder filling per CGA G-4.1 and ISO 8573-3.

FAQ

What is the recommended calibration interval for these instruments?
For GMP/GLP-regulated environments, annual calibration verification is recommended. DMT143 is specified for up to two years between calibrations under stable conditions; EA2 and DMT152 require annual traceable recalibration to maintain ±2 °Cdp accuracy.
Can the DMT152 measure dew point below −80 °Cdp?
No—the DMT152 is specified for −80 to −20 °Cdp. For measurements below −80 °Cdp (e.g., −100 °Cdp), chilled mirror hygrometers (e.g., Michell Optidew) or cavity ring-down spectroscopy (CRDS) analyzers are required.
Is oxygen purge functionality available on all models?
Oxygen sweep capability is standard on the EA2 for inert atmosphere conditioning; DMT143 and DMT152 do not incorporate active purge but rely on flow-assisted sensor stabilization.
Do these transmitters support Modbus TCP?
No—only RS-485 Modbus RTU is supported. Modbus TCP requires an external protocol gateway or industrial Ethernet converter.
Are replacement sensors field-serviceable?
Yes—EA2 sensor cartridges and DMT143/DMT152 sensor modules are user-replaceable with factory calibration data stored onboard; no reconfiguration is needed post-swap.