Assay Technology, Inc. - Miller-Nelson Test Atmosphere Generators









The flow, temperature and relative humidity are set to the desired level using direct reading dial potentiometers. Air flow is measured and controlled using an electronic mass flow controller. A temperature humidity sensor measures the actual conditions. The electronic signals from the sensor form a feedback loop to the controller circuit board. This unit activates heaters in a water reservoir and the humidified air stream to attain and maintain the temperature and humidity conditions. Control functions require no operator intervention except for periodic calibration. All parameters can be observed visually on digital panel meters or monitored with a strip chart recorder. Cooling below room temperature can be achieved using cooling option CP-200.

All HCS-501 series systems control ambient +2 to 35oC (or 20 to 35oC with cooling option) and 20 to 85% RH at 25oC.  They come complete with regulators.  All control systems use 120VAC, 50-60 Hz.

Price List
HCS-501 Brochure

Model HCS-501 Operating Manual

Model HCS-401

Operating Manual


  • Easy to install

  • Fully automatic

  • Digital readout

  • Rapid warm up

  • Direct dial controls

  • 20-85% relative humidity at 25C

  • 20-35C with cooling option

  • 2-20, 5-50, 10-100, 20-200, 25-250, 30-300, and 50-500 L/min air flow ranges available. Custom flow ranges on request.

Instruments Manufactured and Serviced at:

1382 Stealth Street

Livermore, CA 94551 (NEW)

The model HCS-501 series Flow-Temperature-Humidity Control System can be used to produce extremely stable atmospheres for water retention measurements in carbon, gas, sorbents, and desiccants. In addition, this system can produce environments for measuring the effects of humidity on materials, coatings, and gas sensors.

Benefits of the 501 system include improved flow rate accuracy +/-2% from 20% - 100% of full scale. Also, PROM uChip control leads to tighter control of temperature and humidity.

The Model 501 can produce dynamic mixtures with any other gas or vapor desired. Applications include calibration of field and laboratory gas detection devices, calibration of dosimeters and detector tubes, determination of recovery efficiency in sampling tubes and dosimeters, and evaluation of activated carbon service life.  This cost-effective package (20" x 20" footprint) can be used as a generator/controller for a variety of temperature-humidity chambers, in which products, packages, materials, or other test organisms are to be exposed to a specific temperature/humidity regimen. The system can also be used for animal and plant exposure studies.

Respirator Cartridge, Canister and Escape Mask Testing

For Service and Repair:

Contact us at 800-833-1258 or