Posted in | Hygrometers

CR-2 Cryogenic Hygrometer from Buck Research Instruments

Benefits of the CR-2

  • Wide Range: down to -100 °C (15 ppb)
  • Fast Response Time: typically 10-20 seconds
  • Inherent Stability and Accuracy
  • NIST-traceable
  • Very Low Maintenance

The CR-2 exhibits the same wide range, fast response and high reliability as the CR-1A, but it is designed specifically for aircraft and similar high-stress applications. Instead of using Liquid Nitrogen (LN2), mirror cooling is accomplished using a tactical cryocooler, which is a high-tech device used primarily to cool IR detectors in missiles and tank turrets to LN2 temperatures.

Maintenance requirements for the CR-2 are minimal. Aside from occasional mirror cleaning, the cryocooler needs to be renewed every 10,000 hours of use. Both the control circuitry and the sensing assembly are mounted together into a single compact unit. A separate display module is provided that displays the dew / frost point and housekeeping signals. (For aircraft operation, the display module is not required.)

The CR-2 include a ±0.1% accuracy pressure transducer, essential in demanding applications for compensating the dew/frost point temperature for minute differences between sample chamber pressure and atmospheric pressure.

CR-2 Hygrometer Specifications

Measurement Range    
  Dew / frost point temperature -100 to +30°C
  Lowest Concentration ppbv 15
Reading Accuracy °C    
  Entire Range ±0.1°C
  Concentration ±2%
Typical Response Time 10-20 seconds  
Operating Range    
  Temperature -40 to +60°C
  Pressure, psia (bar) 5 to 30 psia (0.3 to 2 bar)
  Air / Gas flow range 0.2 to 3 liters/min
  Altitude 0 to 25 km
Cooling Mechanism Stirling Cycle Cryocooler  
Power Requirements    
  Standard 28 vdc, < 50 W
  Optional 115-220 vac, 50-400Hz, < 50 W
  Outputs 0-10V, 4-20mA, Alarm, RS-232

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