G9 Humidity Generator

RH Systems G9 Humidity Generator

Precision Humidity Generation

The Model G9 produces highly accurate humidity values based on the NIST proven “two-pressure” humidity generation technique. This system will generate a variety of humidity values such as %RH, dew point, frost point, ppm, or vapor pressure. The system is computer controlled, allowing it to run at fixed points, or multipoint profiles, completely unattended.

Principle of Operation

Using the two-pressure technique, humidity is generated by fully saturating gas at a known temperature and pressure, then reducing the pressure to a lower value (typically ambient) at the same temperature. The humidity produced by this technique is determined solely from measurements of temperature and pressure, and does not rely on measurement of the water vapour content.

High Temperature, High Flow Capability

With chamber temperatures up to 85°C and flow rates to 150 standard liters per minute, the G9 boasts the highest temperature, highest flow rate capability of any commercially available two-pressure humidity generator.

Accurate Formulations

All equations programmed into the computer control system are high accuracy, internationally accepted formulations for vapor pressure, enhancement factor, relative humidity, dew point, frost point, ppm and others. Accuracy of the system relies completely on the accuracy of the temperature and pressure measurements.

Air or Water Cooled Refrigeration

Unlike other two-pressure systems, use of cooling water with the G9 is optional. If available, it can be connected and will work to provide cooling of the refrigeration system. If not available, the system reverts automatically to an air-cooled refrigeration mode.


We reserve the right to change design or technical data without notice.


Generator Ranges:
Relative humidity (from 5 to 75 °C) 10…99 %RH
Frost point -21 …0 °C
Dew point -23 …+75 °C
Bath temperature range 5 …+85 °C
Flow rate 25 …150 slpm
Saturation pressure – Low range Ambient …1500 hPa
(Ambient …23 psia)
Saturation pressure – High range 1500 …12000 hPa
(23 …175 psia)
Test chamber pressure Ambient
RH resolution 0.01 %RH
RH accuracy ±0.3 %RH
Bath temperature resolution 0.005 °C
Bath temperature control stability ±0.02 °C
Bath temperature uniformity 0.04 °C
Bath temperature measurement accuracy ±0.02 °C
Gas flow rate resolution 0.1 slpm
Gas flow rate accuracy ±4 slpm
Saturation pressure accuracy – Low range ±0.15 hPa
(±0.0023 psia)
Saturation pressure display resolution – Low range 0.1 hPa
(±0.001 psia)
Saturation pressure accuracy – High range ±1.4 hPa
(±0.02 psia)
Saturation pressure display resolution – High range 1 hPa
(±0.01 psia)
Test chamber pressure accuracy ±0.15 hPa
(±0.0023 psia)
Test chamber pressure resolution 0.1 hPa
(±0.001 psia)
Standard Features:
Gas type Air or Nitrogen
Gas pressure rating (MAWP) 200 psig
Additional Information
Electrical power 200-240 VAC, 30A, 1-phase, 50-60 Hz
Gas supply Max. 1.7 MPa @ 200 slpm, oil free
(Max. 250 psig @ 7 scfm, oil free)
Cooling water (optional) 3 gpm (12L/m) maximum @ 20-25 °C
Operating temperature +15 …+30 °C
Storage temperature 0 …+50 °C
Humidity 5 …95 %RH, non-condensing
Test chamber dimensions 300 mm x 300 mm x 300 mm
Physical dimensions 0.5 m x 1.2 m x 0.9 m