Humidity Generator

The Humidity Generator is designed for fast and precise humidity control for small chambers. Generation of the gas flow directly at the target volume ensures fast control response time even for large changes in relative humidity. The humidity is generated by circulating nitrogen gas inside thermalised H2O and D2O reservoirs. It is also possible to mix nitrogen with an optional gas circulating in an optional liquid. In this case, the user selects the nature of the gas from a long list of gases already implemented in the mass-flow controllers.

The generator is operated by a Process Logic Controller M251 from Schneider and connected to a thermostatic bath regulating the base temperature of the Peltier elements controlling the temperature of the reservoirs. From the temperature and humidity setpoints, the total flow rate and the relative flow rates of D2O and optional liquid/gas provided by the user, the PLC determines the appropriate temperatures of the 8 reservoirs and the flow rates of the 8 mass-flow controllers.  The touch screen graphical user interface displays the evolution of the physical parameters, the actual operated humidity chamber and other parameters.

As startup, the controller is in local mode (i.e. not accessible remotely) and waits for its connection to a nitrogen line or bottle. It checks the levels of liquids (H2O and D20) and proceed a refill if needed. Once feed with nitrogen gas, the controller is ready for operation and allows operations which depend on the availability of liquids and optional gas.

40001ReadRealTemperature setpoint (°C)
40003ReadRealRelative humidity setpoint (%RH)
40005ReadRealTotal flow-rate setpoint (sccm)
40007ReadRealD2O flow ratio setpoint (%)
40009ReadRealOptional flow ratio setpoint (%)
40011Read/WriteRealTemperature setpoint (°C)
40013Read/WriteRealRelative Humidity setpoint (%)
40015Read/WriteRealTotal flow setpoint (sccm)
40017Read/WriteRealD2O flow ratio setpoint (%)
40019Read/WriteRealOptional flow ratio setpoint (%)
40021ReadRealSample chamber temperature (°C)
40129Read/WriteIntegerNOMAD Control — Year
40130Read/WriteIntegerNOMAD Control — Month
40131Read/WriteIntegerNOMAD Control — Day
40132Read/WriteIntegerNOMAD Control — Hour
40133Read/WriteIntegerNOMAD Control — Minute
40134Read/WriteIntegerNOMAD Control — Second
40201ReadBoolean (bit 0)Optional gas source (0:wet, 1:dry)
 ReadBoolean (bit 1)Nitrogen gas source available
 ReadBoolean (bit 2)Optional gas source available
 ReadBoolean (bit 3)Optional gas, wet line in use (calculated RH not reliable)
 ReadBoolean (bit 4)Regulation alarm
 ReadBoolean (bit 5)Regulation default
 ReadBoolean (bit 6)Setpoints discordance
 Read/WriteBoolean (bit 7)Select optional gas line mode (0:wet, 1:dry)
40202ReadBoolean (bit 0) 
 ReadBoolean (bit 1)NOMAD Control — Idle bit
 ReadBoolean (bit 2)NOMAD Control — Running bit
 ReadBoolean (bit 3)NOMAD Control — Local (0) / Remote (1) bit
 Read/WriteBoolean (bit 4)NOMAD Control — Default Acknowledgment bit
 Read/WriteBoolean (bit 5)NOMAD Control — Update PLC clock bit