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The 207 Temperature and RH probe (pn 8713) consisted of a thermistor for temperature measurement and a Phys-Chem Scientific Inc. PCRC11 RH chip (also retired) for RH measurement. The BetaTHERM 100KA61 thermistor used in the 207 was identical to those used in the 107 and 108 temperature probes.
The PCRC11 was suitable for measurements in the 12 to 100% RH range. The RH sensor was particularly susceptible to sulfur and oil gases or compounds, including tobacco smoke. The users needed to avoid direct contact with their skin. The PCRC11 had a shelf life of approximately one year; chip replacement was recommended every six to twelve months.