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.

0ReadRealTemperature setpoint (°C)
2ReadRealRelative humidity setpoint (%RH)
4ReadRealTotal flow-rate setpoint (sccm)
6ReadRealD2O flow ratio setpoint (%)
8ReadRealOptional flow ratio setpoint (%)
10Read/WriteRealRequested temperature setpoint (°C)
12Read/WriteRealRequested relative Humidity setpoint (%)
14Read/WriteRealRequested total flow setpoint (sccm)
16Read/WriteRealRequested D2O flow ratio setpoint (%)
18Read/WriteRealRequested optional flow ratio setpoint (%)
20ReadRealSample chamber temperature (°C)
22ReadRealSample chamber therm. bath temperature (°C)
24Read/WriteRealRequested sample chamber therm. bath temperature setpoint (°C)
26ReadRealMFC #1 flow-rate of N2 dry line (sccm)
28ReadRealMFC #2 flow-rate of N2 dry line (sccm)
30ReadRealMFC #3 flow-rate of H2O saturated line (sccm)
32ReadRealMFC #4 flow-rate of H2O saturated line (sccm)
34ReadRealMFC #5 flow-rate of D2O saturated line (sccm)
36ReadRealMFC #6 flow-rate of D2O saturated line (sccm)
38ReadRealMFC #7 flow-rate of optional line (sccm)
40ReadRealMFC #8 flow-rate of optional line (sccm)
42ReadRealTemperature of H2O bath #1 (°C)
44ReadRealTemperature of H2O bath #2 (°C)
46ReadRealTemperature of D2O bath #3 (°C)
48ReadRealTemperature of D2O bath #4 (°C)
50ReadRealTemperature of optional line bath #5 (°C)
52ReadRealTemperature of optional line bath #6 (°C)
54ReadRealHeater temperature of N2 dry line (°C)
56ReadRealHeater temperature of optional line (°C)
58ReadRealPressure in H20 saturated line (bar)
60ReadRealPressure in D20 saturated line (bar)
62ReadRealPressure in optional wet line (bar)
128Read/WriteUnsigned IntegerNOMAD Control — Year
129Read/WriteUnsigned IntegerNOMAD Control — Month
130Read/WriteUnsigned IntegerNOMAD Control — Day
131Read/WriteUnsigned IntegerNOMAD Control — Hour
132Read/WriteUnsigned IntegerNOMAD Control — Minute
133Read/WriteUnsigned IntegerNOMAD Control — Second
200ReadBoolean (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)NOMAD Control — Setpoints discordance
 Read/WriteBoolean (bit 7)NOMAD Control — Select optional gas line mode (0:wet, 1:dry)
 ReadBoolean (bit 8)
 ReadBoolean (bit 9)NOMAD Control — Idle
 ReadBoolean (bit 10)NOMAD Control — Running
 ReadBoolean (bit 11)NOMAD Control — Local (0) / Remote (1)
 Read/WriteBoolean (bit 12)NOMAD Control — Default Acknowledgment
 Read/WriteBoolean (bit 13)NOMAD Control — Update PLC clock