- 0.5 %RH Uncertainty *
- Traceable to NIST
- Self Contained and Mobile
- Automated Control of User Setpoints
- 2500 ControLog® Automation Software
- HumiCalc® with Uncertainty Software
- Computerized Internal Transducer Calibration
- Low Noise Air Compressor with Air Dryer
- RS-232C Serial Interface
Principal of Operation
The Model 2500 Benchtop Humidity Generator operates using an on board multifunction CPU in conjunction with other peripheral cards to perform calculation and control functions. The embedded computer control system allows the 2500 to generate known humidity levels unattended, freeing the operating technician from the task of system monitoring and adjustment. A computer and/or printer may be connected via the bi-directional RS-232C interface ports allowing remote setpoint control and continuous acquisition of system data. Humidity and temperature setpoint values are input by the operator from the front panel keypad while visual indications of system status are displayed in real time on the liquid crystal display.
All control and measurement parameters critical to the operation of the humidity generator are displayed on this screen. Each parameter in the left most column is identified with a brief title and corresponding units. The generator operates in a variety of user selectable pressure, temperature, and flow units. Some of these are °C, °F, psi, "Hg, Tor, mbar, kPa, l/m, l/h, cfm and cfh. Humidity is calculated and displayed in percent relative humidity (%RH). The asterisk in the left most column indicates the active humidity control parameter. The "SetPnt" column lists control setpoints and the "Actual" column lists all of the measured data and calculated parameters of the generator.
The system utilizes a fluid jacketed test chamber for extremely stable temperature control. Temperature setpoint control is attained by controlling the temperature of the circulating fluid medium that jackets the test chamber and associated humidity generation components. Chamber and saturation temperatures are governed by this medium and are digitally controlled by the computer at any value between 0 °C and 70 °C using PID (proportional-integral-derivative) algorithms.
Pressure And Flow Control
Pressure control and mass flow control are accomplished through computer actuation of electromechanical valve assemblies. Pressure and flow are measured continuously and controlled using PID algorithms similar to those employed in temperature control.
The 2500 humidity generator employs an integral programmatic calibration scheme allowing the temperature and pressure transducers to be calibrated while they are electrically connected to the humidity generator.
Calibration / Display Screen
Coefficients for each transducer are calculated by the computer and stored in the system’s nonvolatile memory until the next calibration is performed.