DG-2, DG-3, DG-4, DG-5 and VDS Humidity Generators

The Michell range of dew-point generators provides flexibility and control at a competitive price. Based on the volumetric mixing of dry and wet gases, the instruments can be controlled either manually or automatically to suit a wide range of calibration applications.

For a complete dew-point calibration system with optional compressor, dryer, dew-point generator and cooled mirror reference instrument refer to DCS System page.

Product Features

  • Manual selection, push button or computer control of generated dew point
  • -100 to +20°C dew-point range capability, depending on model
  • Precision flowmeter or mass flow controller operation
  • High stability and repeatability
  • Fast response to changes in set-point
DG-2, DG-3, DG-4, DG-5 and VDS


The DG3 is our entry-level, single-stage mixing humidity generator. It is operated by manually mixing the two gas streams using flow control valves. The DG3 provides flows up to 5 Nl/min (10.6 scfh) and generates dew points ranging from -40 to +20°Cdp (-40 to +68°Fdp).


The DG2 has two stages of gas-flow mixing which allow it to generate dew points down to -75°Cdp (-103°Fdp). The great strengths of the DG2 are its ease of use and its flexibility in manually generating an accurate target dew point by fine tuning the gas mix via its flow metering valves. Infinite mixing is achievable within its working range.


The DG4 is a two-stage push-button dew-point generator which operates in the range of -75 to +20°Cdp (-103 to +68°Fdp). It can be delivered with between 3 and 10 factory-set dew point settings, selectable from the front panel keypad. Its RS232 communication port enables further automation, particularly when used in conjunction with a UKAS certified hygrometer. The DG4 offers maximum flexibility via its pre-set values combined with the mixing ability of the DG3.


The VDS3 is a sophisticated computer controlled dewpoint generator that operates in the range of -100 to +20°Cdp (-148 to +68°Fdp). Individual three stage mass flow controllers select precise proportions of wet and pre-mixed air. Humidity injection is achieved by a liquid mass flow controller and controlled evaporation system. The Vapor Delivery System (VDS) gives repeatable and flexible control of the generated dew point and can be programmed with up to 13 presets that can be activated manually or as part of an automatic calibration program.

Technical Specifications (DG2, DG3, DG4)

Model DG2 DG3 DG4
Mixing Stages 2 stage 1 stage 2 stage
Humidity Range -75 to +20°Cdp (-103 to +68°Fdp) -40 to +20°Cdp (-40 to +68°Fdp) -75 to +20°Cdp (-103 to +68°Fdp)
Gas Supply7 Nl/min (14.8 scfh) @ 0.68 barg (10 psig) and -75°Cdp (-103°Fdp)
Gas Output1 to 5 Nl/min (2.1 to 10.6 scfh) air @ 0.5 to 1 barg (7 to 14 psig)
FilterParticulate filter
Saturator Polycarbonate and porous polyethylene sinter
HeatingFinned heating elements, 500 watts, fan circulation
Power Supply220 to 240 V, 50Hz or 100 to 120 V; 60Hz
Storage Temperature+5 to +40°C (+41 to +104°F) (with saturators empty)
Operating Temperature +18 to +24°C (+64 to +75°F)
Enclosure Size19" sub-rack x 12U high x 400mm
(15.8") deep
19" sub-rack x 6U high x 340mm (13.4") deep
Enclosure Size20kg (44lbs)9kg (20lbs)25kg (55lbs)

Technical Specifications (VDS3)

Model VDS3
Dew-point range -100 to +20°Cdp (-148 to +68°Fdp)
(factory default preset values= –100, -90, -80, -70 -60, -50, -40, -30, -20, -10, 0, +10 and +20 °C (+68°F))
Output stability ±0.5°C
Required Gas Supply30 Nl/min (63.6 scfh) @ 4.8 barg (70 psig) pressure
<13.8 ppbV (–100°C / -148°F atmospheric dew point) moisture content
Gas Output10 Nl/min (21.2 scfh) @ 0.5 barg (7.3 psig)
Cable ConnectionUSB (type B) for PC Control RS485 (9 way D plug) for Setup
Water Reservoir Material: ABS
Capacity: 1 litre
Power Supply220 to 240 V AC or 100 to 120 V AC 50/60 Hz
Power Consumption500 Watt maximum
Power Connector3 pin IEC
Power Supply Fuse 3A (F) quick blow
Operating Temperature+10 to +40°C (+50 to 104°F)
ConstructionPainted diecast aluminum enclosure with smoked glass door.
Overall dimensions: 1020 x 555 x 600mm (40 x 22 x 24") (h x w x d)
Weight65kg (143lbs) maximum

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