Topic: Grasping at straws to fix Humidity on VP1

[davidmc36]

I was just reading a couple threads:\

https://www.wxforum.net/index.php?topic=42718.msg435983;topicseen#new

https://www.wxforum.net/index.php?topic=40989.0

Got me to thinking. Although the Hum sensor for VP1 is not available......what do we know about how it feeds data to the ISS.

The sensors mentioned in the threads seem to be 5V supplied. So do these work by sending power and reading the change on the way back......totally simplified way to say it I know......could another analog sensor be employed with possibley the "Return Signal" treated by some Arduino or something to give the response the ISS is looking for.

I have three VP1's that I hate to have running with no proper humidity data.

Thoughts??

[johnd]

You may think this is a non-sequitur, but did you do the 2 new WFL videos or was that another David?

[davidmc36]

10-4, that was me. Doing a bit of stuff for Wojtek.

[kobuki]

The VP1 uses a capacitive type hygrometer, not a digital one, so it changes its reactance with RH. That is in turn measured in the SIM by means of a timer, IIRC. So in effect you need to emulate an RH dependent capacitor in the several hundred pF range. With a DAC (emulating the charge/discharge cycle voltage curve) or some quirky method and a clever circuit it might be possible.

Alternatively, you could use standalone transmitters on separate station IDs, original Davis or Arduino-based. Or something that's entirely separate, even from Davis tech. Or you can say an emotional goodbye and get replacement VP2 SIM boards.

EDIT: also, things like digitally tunable caps exist, apparently...

[Aardvark]

you still have working vp1s.   I think to calibrate you could do the offsets on the console,

[kobuki]

That's most definitely a way to handle things. Though OP mentions "no proper humidity data", but not what it entails. Usually the sensed range shrinks considerably, mainly from the top of the scale, and offsetting/scaling it might not make much sense.

[davidmc36]

That's right. Offset will do no good. It is the typical VP1 sensor that is OK up to around 60. Then it goes up exponentially faster than it should and reads 100 when real is only like 85 or so.

The other sensor just sits flat at 35.

[davidmc36]

you still have working vp1s.   I think to calibrate you could do the offsets on the console,

And yeah, I have two ISS VP1 and 3 consoles.

[kobuki]

The other sensor just sits flat at 35.

What other sensor? Is it a specific fault condition with that? Is it frequent?

[johnd]

And what type of VP1? Is it the original VP1 with T/H on the main SIM board (and squarish elements to the radiation shield) or the revised version with the separate T/H, more like a VP2?

[davidmc36]

I have two ISS both with the sensors in the shield. I never even knew about any other type "on board's sensors.

One just sits flat at 35 the other goes off scale above 60ish