SMARTRO SC42 Professional Digital Hygrometer Indoor Thermometer Room Humidity Gauge Pro Accuracy Calibration

Extremely accurate and easy to read — best hygrometer I’ve owned
I picked up the SMARTRO SC42 Professional Digital Hygrometer about two months ago to monitor my master bedroom because of bathroom with shower. This thing is impressive right out of the box. The 3.5″ LCD screen is large and clear, with big digits that are easy to read even from across the room. The touch-activated backlight is a nice touch — it lights up for about 10 seconds when you tap the top, perfect for checking at night without turning on a lamp.Accuracy seems spot-on. It uses industrial-grade sensors (Swiss-made, according to the specs) and updates every 10 seconds. I compared it side-by-side with a couple of other thermometers/hygrometers I own, and it consistently matched or beat them. Temperature is within ±0.5°F and humidity within ±2% RH, which is excellent for this price range. I love that it shows 24-hour and all-time high/low records too — super helpful for tracking how my AC or humidifier is doing.It also has a comfort indicator that tells you if the room is too dry, too humid, or just right. Setup was basically plug-and-play (2x AAA batteries, not included). It comes with a stand, magnetic back, and hanging hole, so you can place it anywhere. No real complaints so far — battery life is solid, and it feels well-built. If you want a reliable indoor consumer thermometer/hygrometer this one is a winner. Highly recommend.

One yr later still accurate.
After having this for almost a full yr, here’s an honest review:The problem with anything like this is knowing if they are truly accurate or not.It’s now the end of July’24. I bought a large display clock that also shows date, day and temperatureback in April. It’s one that I can easily read from across the room–even in the middle of the night because it’s backlit.Anyway, I’ve been checking the two against one another. would you believe they are almost always showing the same temperature even though not sitting next to one another, although in the same~ 250 sq. ft. room. I guess that means either they’re both right or they’re both wrong. If wrong, what are the odds they’d both be wrong by the same amount/temperature. I lean towards they’re both accurate!.Now here’s what I don’t like about it:1) It’s back lit –as long as you turn it on, and then it shuts off automatically. The problem with this one, although it has the backlighting, you have to touch the light icon on the top of the frame to turn it on. That means, for example, if you have it sitting on a shelf and you’re in bed, you have to get up out of bed to go touch the light icon to turn the back lighting on so you can see the display. Therefore, it either has to be sitting on the nightstand right next to you, or you have to get out of bed to go touch it to see it in the middle of the night. It runs on two AAA batteries. If I were to have to change the batteries once a yr instead of every yr and half, that would be fine by me to be able to see/read it in the dark. I know some people are bothered by any light in a room, so maybe an option to either have the back lighting always on or always off. The other option would be to have a light sensor and when the ambient light in the room is dark, the light comes on and it goes off when the room gets light again– kind of like the auto adjustment on my laptop.2) Positioning of readouts:The humidity is displayed on top and the temperature is on the bottom. I can’t reverse the positions though I’d like to. I care a lot more about the temperature inside than the humidity and the top figure is easier for me to see at a distance. Living in the PNW it’s always humid to some degree– inside, my home is normally good. If it should get too dry in here during the winter, I tend to know it by the uncomfortable dryness in my nasal passages &/or a sinus headache above my eyes. Anyway, I’d like to have the temperature displayed on top and the humidity on the bottom. or have the choice of which is displayed where.3) Suddenly this evening, a gray shadow has shown up on the display when lit. It covers probably 7/8th of the display surface–only a little at the very top and at the very bottom aren’t affected. However, even with the shadow, I can still read it the display. I don’t know if it’s simply because the batteries are old or if there’s something else causing it. Hold on a sec and we’ll find out. Nope! Not the batteries–something else. Those weren’t even the original batteries I just replaced. Although fresh batteries made the display brighter, the shadow is still there covering most of the display. So it must be something in the digital display itself or the chip for it. Since I bought this in the summer of ’23, the chip could quite possibly be one made during Covid. There have been problems with some chips made during that time when so much of the world’s industries were shut down or running on skeleton crews. Maybe I just need to replace this entire unit instead of the batteries. Although this isn’t one of the least expensive ones, it’s MSRP was $21.95; with a sale price + a 15% coupon, I paid over $15.00 for it—about twice as much as the least expensive ones on Amazon right now. To be fair, they aren’t back lit and this is. Still, I’ve had it for a few weeks under 1 yr and would expect to get more use than that out of any of them.I guess now, my bottom line is:: buyer beware! You may only get ~1 yr’s use. If you want to consider this a throw away and replace it annually, it does appear to be accurate.

Just what I needed
Have needed this forever. Works great, gives me a more accurate read in the house (which is a metal home). Shows temperature and variations. Has easy to read “humidity” section. Did not realize it had a magnet until I put it close and it basically jumped out of my hand to the wall…so I can guess it is a good one…Worth the money. Have not used the bluetooth and probaly will not.

Excellent in Gun Safes
I’ve had 2 of the Smartro SC42’s for 4 yrs now one in my rifle safe & one in my Large pistol safe. They are Excellent & Accurate. It’s such a piece of mind to open your safe & know the Temperature & Humidity are where they need to be. If one of them ever fails I will replace with the same meter. I love knowing the guns are being stored properly. A must have for owners of multiple firearms.

I use it for keeping my acoustic guitars at the right humidity levels (40~50%) which need an ajustable calibration offset controls (use humidity pack for control reference). Works fine and nice to have a readout backlighting when needed… (Cheaper hygrometers have no controls and can often be inaccurate up to 10%…)

He tenido muchos de estos y este es muy preciso, además se ilumina al moverlo, vale la pena el dinero q vale.

Ottimo igrotermometro. Alla fine ne ho acquistati tre…. Dopo averne resi due di altro produttore che non ho trovato affidabili e che non permettevano la calibrazione se non in un piccolo range ristretto, inutile nel mio caso. Mentre questo permette una calibrazione senza vincoli !!!Ottimo prodotto.