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.

PLC Registers (Schneider M251)

Address	Access	Type	Description
0	Read	Real	Temperature setpoint (°C)
2	Read	Real	Relative humidity setpoint (%RH)
4	Read	Real	Total flow-rate setpoint (sccm)
6	Read	Real	D2O flow ratio setpoint (%)
8	Read	Real	Optional flow ratio setpoint (%)
10	Read/Write	Real	Requested temperature setpoint (°C)
12	Read/Write	Real	Requested relative Humidity setpoint (%)
14	Read/Write	Real	Requested total flow setpoint (sccm)
16	Read/Write	Real	Requested D2O flow ratio setpoint (%)
18	Read/Write	Real	Requested optional flow ratio setpoint (%)
20	Read	Real	Sample chamber temperature (°C)
22	Read	Real	Sample chamber therm. bath temperature (°C)
24	Read/Write	Real	Requested sample chamber therm. bath temperature setpoint (°C)
26	Read	Real	MFC #1 flow-rate of N2 dry line (sccm)
28	Read	Real	MFC #2 flow-rate of N2 dry line (sccm)
30	Read	Real	MFC #3 flow-rate of H2O saturated line (sccm)
32	Read	Real	MFC #4 flow-rate of H2O saturated line (sccm)
34	Read	Real	MFC #5 flow-rate of D2O saturated line (sccm)
36	Read	Real	MFC #6 flow-rate of D2O saturated line (sccm)
38	Read	Real	MFC #7 flow-rate of optional line (sccm)
40	Read	Real	MFC #8 flow-rate of optional line (sccm)
42	Read	Real	Temperature of H2O bath #1 (°C)
44	Read	Real	Temperature of H2O bath #2 (°C)
46	Read	Real	Temperature of D2O bath #3 (°C)
48	Read	Real	Temperature of D2O bath #4 (°C)
50	Read	Real	Temperature of optional line bath #5 (°C)
52	Read	Real	Temperature of optional line bath #6 (°C)
54	Read	Real	Heater temperature of N2 dry line (°C)
56	Read	Real	Heater temperature of optional line (°C)
58	Read	Real	Pressure in H20 saturated line (bar)
60	Read	Real	Pressure in D20 saturated line (bar)
62	Read	Real	Pressure in optional wet line (bar)
128	Read/Write	Unsigned Integer	NOMAD Control — Year
129	Read/Write	Unsigned Integer	NOMAD Control — Month
130	Read/Write	Unsigned Integer	NOMAD Control — Day
131	Read/Write	Unsigned Integer	NOMAD Control — Hour
132	Read/Write	Unsigned Integer	NOMAD Control — Minute
133	Read/Write	Unsigned Integer	NOMAD Control — Second
200	Read	Boolean (bit 0)	Optional gas source (0:wet, 1:dry)
-	Read	Boolean (bit 1)	Nitrogen gas source available
-	Read	Boolean (bit 2)	Optional gas source available
-	Read	Boolean (bit 3)	Optional gas wet line in use (calculated RH not reliable)
-	Read	Boolean (bit 4)	Regulation alarm
-	Read	Boolean (bit 5)	Regulation default
-	Read	Boolean (bit 6)	NOMAD Control — Setpoints discordance
-	Read/Write	Boolean (bit 7)	NOMAD Control — Select optional gas line mode (0:wet, 1:dry)
-	Read	Boolean (bit 8)	—
-	Read	Boolean (bit 9)	NOMAD Control — Idle
-	Read	Boolean (bit 10)	NOMAD Control — Running
-	Read	Boolean (bit 11)	NOMAD Control — Local (0) / Remote (1)
-	Read/Write	Boolean (bit 12)	NOMAD Control — Default Acknowledgment
-	Read/Write	Boolean (bit 13)	NOMAD Control — Update PLC clock