In June 2005, the HMP50 Temperature and Relative Humidity Probe replaced the CS500. The HMP50, manufactured by Vaisala, uses a 1000 Ohm platinum resistance thermometer (PRT) to measure air temperature for the range of -25° to 60°C, and the INTERCAP® capacitive chip to measure RH for the range of 0 to 98%. The chip is field-replaceable, eliminating the downtime often required for the recalibration process.
