Pyranometer vs UV Sensor vs PAR Sensor: What's the Difference?
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Pyranometers, UV sensors and PAR sensors all "measure sunlight" — but they answer three completely different questions. Picking the wrong one gives you precise data about the wrong thing. Here's how they differ and which one your application actually needs.
The three questions
- Pyranometer: "How much solar energy is arriving, in total?"
- UV sensor: "How much ultraviolet radiation is there?"
- PAR sensor: "How much light can plants actually use for photosynthesis?"
Pyranometer — total solar radiation
A pyranometer measures the full broadband solar spectrum — roughly 0.3 to 3 μm, covering ultraviolet, visible and near-infrared — and reports total irradiance in W/m². It is the standard instrument of meteorology and the solar energy industry: photovoltaic yield estimates, solar resource assessment and weather station radiation records are all built on pyranometer data.
Our solar radiation pyranometer ($349) uses a high-precision photoelectric element with wide spectral absorption and a dust cover with 95% light transmittance, and offers both RS485 Modbus and 4–20mA output. The SEN101-2015A optical irradiance radiometer ($399) measures the same 0.3–3 μm band with a flange mount, and can be pointed downward to measure reflected radiation — useful for albedo studies, building material degradation and air pollution monitoring.
UV sensor — the ultraviolet slice only
A UV sensor ignores most of the spectrum and measures only the ultraviolet band (roughly 280–400 nm). That small slice is what drives sunburn and UV index, polymer and coating degradation, and many photochemical processes — effects that are invisible in a total-radiation number. A bright but UV-poor day and a UV-intense day can have similar W/m² totals.
The SEN101-UV ultraviolet sensor ($149) uses an integrated UV sensing chip and transmits over RS485 (4–20mA and 0–5V versions are also available). It's used in environmental and meteorological monitoring, agriculture and forestry — anywhere the UV component itself is the variable of interest.
PAR sensor — light as plants see it
Photosynthetically active radiation is the 400–700 nm visible band that drives photosynthesis. A PAR sensor weights its response to match that band, so it reports the light a crop can actually use — not total energy. Two light sources with identical W/m² can deliver very different PAR, which is why greenhouse growers control supplemental lighting by PAR (often expressed in μmol·m⁻²·s⁻¹) rather than by lux or total radiation.
Our PAR sensor ($229) combines high sensitivity with a long RS485 transmission range, and is widely used in greenhouses, laboratories and breeding facilities.
Side-by-side
| Pyranometer | UV sensor | PAR sensor | |
|---|---|---|---|
| Measures | Total solar radiation | Ultraviolet radiation only | Photosynthetically active radiation |
| Spectral band | ~0.3–3 μm (broadband) | ~280–400 nm | 400–700 nm |
| Typical units | W/m² | W/m² or UV index | W/m² or μmol·m⁻²·s⁻¹ |
| Key applications | Solar energy, meteorology, climate research | UV index, material weathering, environmental monitoring | Greenhouses, crop science, lighting control |
| Example price | $349 | $149 | $229 |
Which one do you need?
- Solar plant or weather station? Pyranometer. It's the reference instrument everyone else's data is compared against.
- Greenhouse or indoor farm? PAR sensor for lighting decisions. Many growers add an outdoor pyranometer as well, to relate inside PAR to total incoming solar energy.
- Studying UV exposure, curing, or material ageing? UV sensor — total radiation numbers will mislead you.
- Building a full radiation monitoring point? Combine them. The three overlap in hardware (all are available with RS485 Modbus output, so they share one bus) but not in meaning.
All three sensor types are in our Solar Radiation Sensors collection, each with a downloadable datasheet listing its exact spectral response and output options.