Topic: Vaisala INTERCAP humidity sensor as replacement for analog temp/hum board

[CW7491]

I learned from a member here that the Vaisala HUMICAP180R will work with the old analog Davis temp/hum board. These sensors are the same sensor used in all of the top of the line humidity sensors from Vaisala. While the sensor does work with the Davis, according to Vaisala, the capacitance readings are slightly different from their INTERCAP sensor which uses the exact same chip, but is significantly cheaper ($77 v $161).

After doing some research, I found that Davis actually used to put in their product manuals the option of using a Vaisala HUMITTER temp/hum sensor. The HUMITTER probe used Vaisala's INTERCAP sensor. I've tried both and the HUMICAP reaches 100% humidity, but tends to have a wet bias at dry humidity (same or maybe even a little worse than Sensirion). The INTERCAP on the other hand performs extremely well. It reaches 100% humidity and performs well at low humidity. I've asked Davis and Vaisala if Vaisala produced the original Davis humidity element and neither would confirm, but that is my suspicion.

I've placed the INTERCAP in the same shield side by side with the current Davis digital sensor and it confirms what has already been commented on: the Sensirion sensor reads about 3-8% high below about 40-45% humidity and the Sensirion gets "tight" at high humidity and reports 2-3% low above 80%.

For those of you who need or want to replace your humidity sensor with a Vaisala sensor and have the old analog sensor, the Vaisala INTERCAP is plug and play. There is finally a known replacement for failed humidity elements for the analog VP2. And as the technology and sensor element was the same as I understand it, it should work with the VP1 and WMII as well.

[archae86]

For those of us with old VP2 ISS units, approximately when is the cut-off date when this particular part is not suitable?

[CW7491]

I’m not sure how old your VP2 is, but unfortunately this is only helpful for the very first units produced prior to about 2006 (I think the VP2 came out in 2004 or 2005 so not very long). Anything more recent than that will most likely have a digital temp/hum board with a Sensirion sensor that this will not work with. The part number for the analog temp/hum board that this will work with is 7346.029. I do not recall how long after 2006 these boards were still available, but if I recall correctly it was a few years. I believe the technology for these analog boards is the same that Davis had used in the original VP and the Weather Monitor II. For a long time there was no replacement if the humidity sensor element failed. This solves that problem. As far as I know, the current VP2 ISS is still backward compatible with these analog boards so that if you have one and try to use it with a new VP2 ISS, it should still work. Admittedly this is a very limited use issue that will not benefit or interest most people, but may be helpful to some.