The best solution is to turn off the humidifier altogether, and air-seal the house to the point where low wintertime humidity issues aren't a problem. Dry indoor air in wintertime is a symptom of excessive ventilation/air infiltration. Humidifiers are the band-aid, but it's a remedy that can do more harm than good in the long term.
Humidifiers operated without sufficient care can end up decreasing the indoor air quality by storing enough wintertime moisture up inside your walls to promote high mold-spore counts in the springtime as the average temperature of your wall assemblies increase, releasing that moisture just as it gets to be warm enough for molds to reproduce rapidly.
It's nearly impossible to retro-fit air seal to the point that the house is TOO tight, and most breathing/bathing/cooking humans will provide more than enough moisture to the air to keep it at 30-35% relative humidity @ 70F indoors even during cold snaps, as long as you have at least 2 occupants. Only if you smoke or use a lot of toxic aerosols indoors would you need to ventilate to the point where the indoor humidity levels would be below 30% and begin to feel dry. At 40% RH and above in mid-winter the average temp at exterior sheathing of framed walls in a central PA climate stays below the indoor air's dew point for most of the winter, and loads up. If you're running the humidifier, keeping it at 30-35% will be the best compromise for comfort and human/house health.