Reports

At Vaira from 2024-02-27 to 2024-03-36 we compared a new HygroVue sn E5761 with the old HMP45 sn W0730037 in preparation for continuing measurements of RH and T with the HygroVue.  The old HMP45 has been reading upto 110% RH for several years now.

Overall, the new HygroVue is better.  As to whether we should attempt to correct the old data I am uncertain.  Certainly the RH needs correction and this has already been implemented.  I think this report can act as a place holder and if someone needs more precise RH or T we can look at applying more complicated corrections.

Air Temperature looks pretty tight.  The new sensor is reading a little lower than the old sensor at high values.  Unfortunately we only saw conditions up to about 24C - with this relationship, at 40C the new sensor will be about 1C lower than the old sensor.

Figure 1. Timer series of air temperature.

Figure 2. Regression of air temperature.

Relative Humidity is the main reason the old HMP45 is being replaced.  The old sensor is well above 100% and the new sensor stays just under 100%.  Previously I used a regression for RH above 85% to correct the high values. 

Figure 3. Time series of Relative Humidity.

Figure 4. Regression of Relative Humidity.

Another option would be to use a 5th order equation for the regression.  This fits the data better (maybe - check history), but not yet implemented in the database.