Does this display Humidity or does it display Relative Humidity?

From the Amazon product page, Specifications: "Humidity Range: 1~99%RH(relative humidity)". The Amazon page mentions "RH" at least 9 times, strongly suggesting that is what it displays. Additionally, humidity is the amount of water vapor in a unit volume of air (independent of temperature) which is expressed in kilograms per cubic meter. Relative Humidity is the PERCENTAGE of the maximum amount of water vapor in the air, possible at that temperature. Because the Hygrometer reports a percentage, not a mass per volume, there can be no confusion. RH is what you want for controlling comfort and environmental conditions (mold growth, etc,).

Can this be calibrated if needed?

You can only calibrate if you have a standard that is accurate. You can adjust the reading up and down. I have 7 of these so I put them all in the same room for about 6 hours and I adjusted mine so it matched the rest. The rest were within 2 of each other, this one was 4 so I made it like the others.

can you make the light stay on?

Not as far as I can see. Just a very light tap on the top of the frame will light it up for about ten seconds. That seems more than enough IMHO. If left on too much, the battery would drain sooner. Just a very very light tap.

Your product information states: "calibration certification from aerospace institute for metrology and measurement technology" missing cert. doc?

I have never looked for any certification's. I did a comparison test with 4 different instruments and liked this model best, so I purchased 4 or 5 of them. They have been working fine in my home and hobby woodworking shop.

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

Product ID: 165743724

Details

Battery Description
2x 1.5v AAA
Brand
SMARTRO
Color
black
Item Weight
0.13 Kilograms
Product Dimensions
3.4"W x 3.4"H

📏±0.5℉ & ±2%RH accuracy

🔋Powered by 2x AAA batteries

⏱️Updates every 10 seconds

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Description

🌡️ Stay ahead of the curve with pro-grade climate control!

PRECISION SWISS SENSORS - Experience industrial-grade accuracy with real-time updates every 10 seconds, ensuring you never miss a subtle change.
24 HOUR MAX MIN TRACKING - Stay ahead of environmental shifts with all-time and daily high/low temperature and humidity records.
MANUAL CALIBRATION SUPPORT - Fine-tune your readings for unmatched precision, tailored to your unique environment.
VERSATILE MOUNTING OPTIONS - Magnet, wall mount, or stand—perfectly adaptable to your office, nursery, wine cellar, or greenhouse.
CRYSTAL CLEAR BACKLIT DISPLAY - Large 3.5'' HD LCD with touch-activated backlight for effortless reading anytime, even in low light.

The SMARTRO SC42 is a professional digital hygrometer and indoor thermometer featuring Swiss sensors for ±0.5℉ temperature and ±2%RH humidity accuracy. It updates readings every 10 seconds and offers a large backlit LCD for easy monitoring. With 24-hour max/min records, multiple mounting options, and manual calibration, it’s designed for precise environmental control in homes, offices, and specialized spaces.

Specifications

ASIN	B07YY1FB9D
Battery Description	2x 1.5v AAA batteries
Best Sellers Rank	#3,982 in Patio, Lawn & Garden ( See Top 100 in Patio, Lawn & Garden ) #6 in Weather Hygrometers
Brand Name	SMARTRO
Color	black
Customer Reviews	4.6 4.6 out of 5 stars (7,009)
Included Components	1 thermometer 1 manual
Item Dimensions W x H	3.4"W x 3.4"H
Item Weight	0.13 Kilograms
Manufacturer	SMARTRO
Model	SC42
Mounting Type	Wall Mount
Operating Humidity	1-99% with a +/- 2%RH tolerance
Part Number	SC42EUK
Smart Home Compatibility	Not Smart Home Compatible
Temperature Accuracy	+/-0.5 Degrees Fahrenheit
Temperature Reading Accuracy	plus_minus_0_point_2_degrees_celsius
Unit Count	4.64 Ounce
Upper Temperature Range	158 Degrees Fahrenheit
Voltage	3.0
Warranty Description	13-month warranty except for artificial damages

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$44.40

Duties & taxes included

In stock

Sold byAmazon USADelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to USA.

Secure transaction

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TrustScore 4.5 | 7,300+ reviews

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