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New Precision Trace Moisture Analyser Hygrometer | QMA401

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Michell Instruments has launched its new precision moisture analyser, the QMA401, featuring the latest generation of quartz crystal microbalance (QCM) sensor and designed to provide consistently accurate measurements of trace moisture.

Price Guide (Inc GST): POA

Michell Instruments has announced the launch of its recently enhanced QMA401 Low Maintenance Trace Moisture Analyser. 

Maintaining this new generation quartz-crystal oscillator based analyser is simple, infrequent and inexpensive. No service at all is required for at least 2 years, at which point the desiccant dryer could need replacement – a process that can be carried out by the user in less than 10 minutes. It’s straightforward to replace the internal moisture generator in the field with a freshly calibrated NPL or NIST traceable reference unit from the factory, which will last for a full 3 years of operation. 

The newly designed quartz crystal technology-based hygrometer features an improved touch-screen interface. The menu system is intuitive for easy operation following the structure known from Michell’s premium range of chilled mirror hygrometers. Operators, and service engineers, will be able to switch easily between the S8000 chilled mirror range and the QMA401. The case of the QMA401 has also been redesigned with a modern, easy-clean surface, which is similar in look and feel to the S8000 precision hygrometers. 

Using the new generation of quartz crystal microbalance (QCM) sensor, the QMA401 precision hygrometer provides consistently accurate measurements of trace moisture. This is achieved through an automatic self-calibration system which adjusts the analyser against an internal moisture generator (traceable to NPL and NIST). 

The long maintenance intervals of the product, in combination with the competitively priced spares means that the cost of owning a QMA401 over five years is less than half the cost of owning the next competing product that uses a similar quartz crystal oscillator sample cell.


  • The QMA401 is easy to use with an intuitive touch screen interface for monitoring, logging and configuring parameters.
  • Both real-time trend graphs and alarm indicators are immediately visible in colour on the main display.
  • The instrument is supplied with both analogue outputs, and USB and Ethernet digital connectivity, so that the device can be monitored and controlled remotely via a network.

Typical applications 

Trace moisture measurements in gases with high accuracy and fast response – such as verifying the purity of semiconductor plasma etching gases, monitoring polymer drying for plastic bottle manufacture and monitoring hydrogen cooling systems for power generators.

Measuring technology Fast Response Quartz Crystal Microbalance
Measurement range 0.1 to 2000ppmV
Accuracy ±10% of reading from 1 to 2000 ppmV
0.1 ppmV between 0.1 and 1 ppmV
Repeatability ±5% of reading from 1 to 2000ppmV
±0.1ppmV between 0.1 and 1ppmV
Available units ppmV, ppmW, mg/nm3, vapor pressure (Pa), frost point (°C), lb/MMscf
Response speed T63 <2 mins to step change in either direction
T95 <5 mins to step change in either direction
Sensitivity 0.1ppmV or 1% of reading, whichever is greater
Automatic calibration Internal moisture generator source calibrated traceable to NPL and NIST
HMI 7” color LCD with touch screen
Analog outputs 2 channels: user selectable 4–20 mA or 1 to 5 V
Digital communications USB and Modbus TCP over Ethernet
Data logging Direct logging to SD card or PC via application software
Alarms 1 x System alarm, volt-free change-over (FORM C)
1 x Flow alarm, volt-free change-over (FORM C) settable high or low
2 x Level alarm, for ppmV or DP, settable to be active high or low
Power supply 85 to 264 V AC, 47/63Hz
Operating Conditions
Inlet pressure User-controlled to 1 barg
With optional inlet pressure regulator: 300 barg max
Outlet pressure Atmospheric
Sample flow requirement 300ml/min total flow @ atmospheric pressure
Sample gas temperature 0 to +100°C
Operating environment +5 to +45°C up to 90% RH
Mechanical Specifications
Case 19” x 4U x 434mm Housing
Sample connections 1/4” VCR Swagelok®
Weight 13.5kg

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