HygroGen Humidity Generator for the Calibration of Humidity Probes
The HygroGen humidity generator is designed for the calibration of relative humidity probes. This portable humidity generator is completely self-contained, requiring no external resources except mains power, and is light enough for use on-site.
Suitable for calibrating all types of humidity-temperature probes
Fast equilibrium: typically less than 15 min. to move from one condition to another
Generates an extremely stable humidity and temperature environment
Smart chamber design minimizes temperature and humidity gradients
Range: 5 to 50°C and 5 to 95 %RH
Chamber accepts up to five probes
Data loggers can be inserted in the chamber
Available with different models of chamber door
Stainless steel enclosure facilitates cleaning in pharmaceutical and food applications
Overview
The HygroGen humidity temperature generator uses a mixed flow method for generating the humidity (%RH) required by the user. A desiccant cartridge provides low humidity, a saturator high humidity, and a control system mixes these together to create a constant environment within a well insulated chamber. Temperature is controlled with a Peltier thermoelectric heat pump. Set points are easily adjusted using the front panel controller keypad, or via the RS-232 interface using a PC and optional controller software.
The HygroGen uses a high performance controller to achieve both exceptional stability and rapid stabilization when moving from one condition to another. Smart chamber design, combined with a high rate of air flow, contributes to minimizing humidity and temperature gradients inside the chamber, and to shielding the chamber from the outside environment.
For the purpose of controlling conditions inside the chamber, humidity is measured with a HygroClip S digital probe and temperature with a separate Pt100 RTD. Depending on the model of HygroGen, the reference humidity and temperature used to calibrate humidity instrumentation is usually provided by another set of probes and instruments
(see calibration traceability).
Key Features
1
Dryer cell - removable cartridge filled with a molecular sieve desiccant (can be regenerated)
2
Distilled water tank. Fill or empty by inserting the dosing syringe in the access port located on the front of the unit
3
Multi-loop controller especially configured and tuned for the HygroGen
4
Internal chamber designed to provide a stable calibration environment with minimal temperature gradients.
5
Chamber door - different models available
6
Stainless steel enclosure - facilitates cleaning
Models
HygroGen 1:
Basic humidity-temperature generator. The humidity and temperature reference instrument is either an SCS certified HygroClip S probe or a customer supplied probe inserted through the HygroGen door.
Hygrogen 2:
Humidity-temperature generator with integrated pump for a sampling loop used to connect a user supplied condensation hygrometer (humidity reference). A reference thermometer should be inserted through the HygroGen door.
Calibration Traceability
Calibration of ROTRONIC probes: using the HygroGen, a 2-point temperature adjustment of the ROTRONIC humidity-temperature probes should be done at 20°C and 45°C. Humidity adjustments should be carried out at 35, 80 and 5 or 10%RH, all at 20°C. Obviously, the HygroGen can also be used to calibrate non-ROTRONIC humidity instrumentation.
Humidity and temperature reference:
Preferably, the temperature reference should be provided by a certified precision PRT inserted through the chamber at the same immersion depth as the probes to be calibrated. As an alternative, an SCS certified HygroClip S may be plugged into one of the two spare MOC connectors inside the chamber. We do not recommend using the control Pt100 RTD as the temperature reference.
Depending on the model of HygroGen, the following alternatives are available regarding the humidity reference:
HygroGen 1: use a set of SCS certified HygroClip probes, inserted one at a time through the chamber door at the same depth as the probes to be calibrated. To avoid sensor hysteresis and loss of accuracy, each probe of the reference set should be used exclusively at a defined humidity value (example: 10, 35 and 80%RH for 3 probes). When not in use, the probes should always be stored in a dry environment. We do not recommend using the control HygroClip S as the humidity reference.
HygroGen2: use a certified condensation hygrometer connected to the HygroGen (this model has an internal air pump to circulate air through an external sampling loop).
Limitations of humidity sensors based on a polymer:
When the humidity reference is provided by a probe with a polymer sensor, the user should beware of so-called sensor hysteresis. Sensor hysteresis occurs when a polymer sensor is exposed to humidity above 50 to 60 %RH and results in a temporary positive calibration shift when the sensor is returned to lower humidity. The magnitude of the calibration shift depends on the maximum humidity to which the probe was exposed, on the duration of the exposure and on the make of sensor.
Specifications
Control range maximum
5...95%RH and 5...50°C
Control range minimum
10...90%RH over the range of 10...50°C
Humidity control stability
(peak to peak)
0.02%RH at 5%RH to 0.35%RH at 95%RH and 20°C
0.11 %RH at 15 %RH and 45°C
0.50 %RH at 10%RH to 0.35%RH at 90 %RH and 5°C
Temperature control stability
(peak to peak)
0.03°C or better from 5 to 45°C (at any humidity value)
Temperature gradient limit 1
0.10°C or better from 20°C to 45°C and 15 %RH to 80 %RH
Humidity gradient limit 1, 2
0.2 %RH or better from 5 to 80%RH
1.7 %RH or better at 95 %RH
Time to set point
35 to 80 %RH change at 20°C: 5 minutes or better
20 to 45°C change: 20 minutes or better
Temperature control probe
Pt100 RTD 1/3 Class B, directly wired to controller
Humidity control probe
ROTRONIC HygroClip S
Chamber volume
2 liters / 122 cu ft
Overall dimensions
455 x 420 x 212 mm / 17.92 x 16.54 x 8.35"
Weight
17 kg / 37.5 lb
Power
110-230 VAC 3A 50-60Hz Class I
1 at a probe immersion depth of 120 mm / 4.7", measured from the back of the door
2 at 20°C
HygroGen Humidity Temperature Map
1:Range of operation
2: Hatched regions indicate conditions when condensation can be expected in the
chamber
;)
