Vaisala HUMICAP HMP155, User Manual, Page: 19 / 102

2.4 Additional temperature probe option
Figure 3 HMP155 with additional T ‑ probe
The additional temperature probe is available for HMP155A and HMP155E.
You can order the active output version of HMP155 with an additional temperature probe (T-
probe). You can make relative humidity and additional temperature measurements with the
additional T-probe, if you have a heated HMP155. The additional T-probe fulfils requirements of
meteorological applications. The response time is faster in temperature measurement and it
fulfils WMO requirement of 20-second time constant.
When the additional T-probe is in use, the relative humidity value is calculated based on the T
d
dew point value from the humidity probe and the T
a
temperature value from the T-probe.
Chapter 2 – Product overview
17