Measuring light (illuminance, as measured in lux or footcandles) is relatively easy; measuring both UV and light is more challenging (thus my long response).
As Anna suggested, the Elsec meter measures both UV and light (illuminance). My quibble with Elsec is that they don't report meeting international standards for accuracy. Still, the Elsec is the easiest (and probably most effective) way to measure UV and LIght, especially since the microwatt-per-lumen calculation is handled within the meter.
The Elsec has two sensors, one tuned to illuminance (peak sensitivity at 555nm) and one for UV (peak sensitivity somewhere around 380nm). A handheld spectrometer that measures both the complete spectrum of visible light and UV is my preferred option, but it's much more expensive. At The Smithsonian American Art Museum I use the GL Optics + Flicker spectrometer. https://gloptic.com/products/gl-spectis-1-0t-flicker/ This instrument is very accurate, meeting DIN 5032-7:1985 at a Class B level and the Japanese standard JIS C 1609-1:2006 at a Class AA level for illuminance (see below for more information about the standards).
There are inexpensive UV meters (around $200) that can be used along with a light meter to measure microwatts per lumen-but the unit conversion to microwatts/ lumen can be tricky. It's also a challenge finding a Uv meters that covers the UV spectrum to 400nm.
The least expensive method of determining whether UV is a problem is to use a UV dosemeter (about $7). Note: these cards do not replace a meter and are not accurate enough to confirm that daylight has no UV component-but they can indicate whether a problem exists that warrants further investigation with a more accurate instrument.
https://www.amazon.com/QuantaDose-Light-Power-Visibility-Technology/dp/B08KZZ54BZ
Smartphones do not provide accurate illuminance measurements (unless they have a separate sensor that connects via Bluetooth). The same goes for some of the small data loggers marketed to the conservation community that claim to provide continuous illuminance and UV feedback. In my experience, these meters may have their uses, but they are not as accurate as a UV or illuminance meter-some of these small dataloggers that report illuminance don't even have a cosine corrector (the small white disk in front of the sensor that is required on every light meter).
Inexpensive illuminance meters, like the one by Amprobe that Anna suggested, are much better. There are lots of choices out there, I recommend meters that can provide a NIST calibration certificate and/ or report their accuracy according to JIS (Japanese) and DIN (German) standards. See the tables below for the accuracy (and inaccuracy) of each meter class-many thanks to Eric Hagan for digging up this information.
At the Smithsonian American Art Museum, I use Minolta or Hioki meters because they comply with the German standard DIN 5032-7:1985 at a Class B level and the Japanese standard JIS C 1609-1:2006 at a Class AA level. If you find others, please let me know (I'm guessing Gossen, at the least, must make one).
Table 1: Limits of cosine error versus angle of incidence for illuminance meter classes defined by JIS C 1609-1:2006
|
Angle of incidence
|
Precise
|
Class AA
|
Class A
|
|
10°
|
±1%
|
±1%
|
±1.5%
|
|
30°
|
±2%
|
±2%
|
±3%
|
|
60°
|
±5%
|
±7%
|
±10%
|
|
80°
|
±20%
|
±25%
|
±30%
|
Table 2: DIN 5032-7:2017-02 and example quality indices
|
Category
|
Class
|
Calibration uncertainty
|
V(λ) mismatch, f1'
|
Directional response, f2
|
Total, ftotal
|
|
Highest quality (laboratory)
|
L
|
1%
|
1.5%
|
–
|
3%
|
|
High quality
|
A
|
1.5%
|
3%
|
1.5%
|
5%
|
|
Medium quality
|
B
|
3%
|
6%
|
3%
|
10%
|
|
Low quality
|
C
|
5%
|
9%
|
6%
|
20%
|
------------------------------
Scott Rosenfeld
Lighting Designer
Smithsonian American Art Museum
Washington
United States
------------------------------
Original Message:
Sent: 10-07-2025 17:02
From: T. McGrew
Subject: Light meters
Hi folks,
I am seeking recommendations for light meters.
My primary need is for a basic affordable digital light meter that includes the capability of measuring UV as well as visible light.
It doesn't need to log results or anything just give accurate readings and hopefully it would be rechargeable.
As a backup it would also be great to have another basic quality meter (that doesn't need to measure UV) and that could be battery powered. Any guidance would be greatly appreciated!
My apologies for any cross posting
Cheers,
Ashley
-- T. Ashley McGrew
Pacifica, CA
(646) 265 - 5526