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Model 2900 -Automated Two-Pressure Humidity Generator
The Model 2900 Humidity Generation System is a self-contained system capable of producing atmospheres of known humidity using the fundamental “two-pressure” principle. This system is capable of continuously supplying relative humidity, dew point, frost point, parts per million, or other calculated values for instrument calibration and evaluation as well as for precision environmental testing. This system will automatically generate manually entered humidity and temperature set points as well as user created multipoint profiles. All desired humidity’s, temperatures, flow rates, and time intervals may be programmed.
- Traceable to SI 1
- 0.5% of Reading RH Uncertainty 2
- High Flow Capability of 50 L/min
- Based on NIST Proven "Two-Pressure" Principle
- HumiCalc® with Uncertainty Mathematical Engine
- ControLog® Embedded Automation Software
- Generate: RH, DP, FP, PPM, Multipoint Profiles
- Externally Driven Chamber Fan
- Multi-point Touch LCD
- Fluid Jacketed Chamber Door
- Window Chamber Door (Option)
The “two-pressure” humidity generation process involves saturating air or nitrogen with water vapor at a known temperature and pressure. The saturated high-pressure air flows from the saturator, through a pressure reducing valve, where the air is isothermally reduced to test pressure at test temperature. Humidity generation is dependent on the measurement of temperature and pressure, not on the amount of water vapor measured in the air. System uncertainty is determined by the temperature and pressure uncertainties, and on the stability and uniformity of the measurements. When setpoint equilibration has been reached, the indication of saturation temperature, saturation pressure, test temperature, and test pressure, are used in the determination of all hygrometric parameters.
The 2900 Humidity Generation System encompasses a high-performance stand-alone Control System that performs all functions required for humidity generation and control. The Control System employs 24 bit I/O modules with integrated signal conditioning to acquire data and uses serial interfaces to transducers and stepper motors to control the operation of generating humidity. The Control System utilizes an embedded operating system in conjunction with specialty software to control and interface with the human to machine interface (HMI) computer that runs ControLog.
ControLog is an embedded software application that fully automates the operation of the 2900 Humidity Generation System and allows various device connections through a number of different interfaces. ControLog uses Thunder Scientific’s HumiCalc with Uncertainty as its mathematical engine for computing all humidity values and real-time uncertainties. Data from the generator and attached devices is automatically retrieved and stored for viewing in either numerical or graphical format in real time or post process. Data can be transferred off the system via a USB drive for further viewing, post processing and printing using an external Windows PC. The ControLog software also provides the primary interface to the operator via the multi-point touch LCD which allows the user to select humidity parameters, pressure, temperature, and flow units. The Parameter Tab is the primary interface for the user and is divided in two sections, Control and Calculated Humidity. Within each tab there are two different tiles, the Setpoint Tile is for the user to enter the desired setpoints and a Value Tile displays the Actual Value.
Temperature Control: The 2900 humidity generation system incorporates a water/glycol jacked test chamber for extremely stable temperature control. The system uses PID (proportional-integral-derivative) algorithms to control the temperature of the chamber fluid as it is pumped around the test chamber and through the saturator at the rate of approximately 14 gallons per minute by a magnetically coupled centrifugal pump.
Pressure And Flow Control: Pressure control and mass flow control are accomplished through computer actuation of electromechanical valve assemblies. Saturation pressure and mass flow are measured continuously and controlled using PID algorithms similar to those employed in temperature control.
Temperature Calibration Coefficients Screen
Calibration: Proper calibration of the temperature and pressure transducers ultimately determines the accuracy of the generator. The humidity generator employs an integrated software calibration scheme allowing the 2900’s probes and transducers to be calibrated while they are electrically connected to the humidity generator. Coefficients for each transducer are calculated by the computer and stored to memory.