I had a couple of mechanical hygrometers in my grow chamber. *I didn't really trust them, so I bought an electronic one.
Very different readings, and I trust it more.
The mechanical hygrometers showed humidity dropping overnight as the temperature dropped (with the lights being off), but I suspected relative humidity should increase, as the air cools and saturates.
The electronic hygrometer showed that happening; it shows relative humidity at >95% overnight, and about 63% during the day.
The dramatic change in relative humidity has to do with how much moisture the air can hold, more than any real drop in the percent makeup of water vapor in the air.
Will such a drop in relative humidity be detrimental to Nepenthes such as N. bicalcarata?