Model 2500

Benchtop “Two-Pressure” Humidity Generation System

The Model 2500 Benchtop Humidity Generator is a self contained system capable of producing atmospheres of known humidities using the fundamental, NIST proven, "two-pressure" principle. This system is capable of continuously supplying accurately known humidity values for instrument calibration, evaluation, and verification, as well as for environmental testing. Simply apply power and the 2500 will power-up ready to generate. Humidity setpoint values are input by the operator from the front panel keypad and are limited only by the range of the 2500 humidity generator. Relative humidities are calculated from the measurements of pressure and temperature with the formula:

%RH= fs/ fc · es/ ec · Pc/ Ps · 100

To generate a known humidity, the computer controls the pressure ratio Pc /Ps utilizing the enhancement factor ratio fs/fc and the effective degree of saturation es/ec. Humidity produced is solely dependent on the measurement of pressures and temperatures and does not rely on any other device (such as a dew point hygrometer, psychrometer, or humidity sensor) for the measurement of water vapor content. Precision humidity generation is determined by the accuracy of the pressure measurements and on the accuracy and uniformity of temperature throughout the generating system.

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Model 2500 Humidity Generation System

End of Life,
News Bulletin.

 Thunder Only offers the "ST" version of this model.

“Due to obsolescence of components, Model 2500 humidity generators that have a serial number of 0105300 or less are no longer supported by Thunder Scientific.”


  • 0.5 %RH Uncertainty 1
  • Traceable to SI 3
  • Self Contained and Mobile
  • Automated Control of User Setpoints
  • 2500 ControLog® Automation Software
  • HumiCalc® with Uncertainty Software
  • Computerized Internal Transducer Calibration
  • RS-232C Serial Interface
  • 2500ST Mobile Cart with an Air Tank, Air Filters and Regulator Assembly
  • Low Noise Air Compressor with Air Dryer (Option)

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1 Uncertainty values represent an expanded uncertainty using a coverage factor, k=2, at an approximate level of confidence of 95%. Uncertainty is not specified at temperatures below 0 °C or at flow rates below 10 L/min.

3 Traceable to the International System of Units (SI) through a national metrology institute (NIST) recognized through a CIPM MRA.

Product Options for (ST)

Here are the options available for the Model 2500ST humidity generation system.

Custom options are available.

Auxiliary items for this model

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Weights & Measures

This table shows the container dimensions and shipping weight.
2500R Generator43" x 30" x 31" (109 x 76 x 79 cm)345 lbs. (157 kg)
2500R Cart/ACS252044" x 28" x 41" (112 x 71 x 104 cm)375 lbs. (170 kg)
2500ST Generator46" x 33" x 34" (117 x 84 x 87 cm)405 lbs. (184 kg)
2500ST Cart/ACS252047" x 30" x 41" (120 x 76 x 104 cm)425 lbs. (193 kg)

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