ULM-500 Universal Light Meter & Data Logger WALZ

Originally, we produced PAR-sensors as accessories for our PAM Chlorophyll Fluorometers. Now, we also offer a fast data logger with a high dynamic range and adequate PAR-sensors for independent PAR-measurements or PAR-monitoring.Our data-logger and sensors are capable of resolving the saturating light pulse of PAM Chlorophyll Fluorometers or fast light flecks in nature.

Light Measurement

The main purpose of the ULM-500 is light-measurement. The ULM-500 has two connectors for light sensors with BNC plugs. Typically, PAR sensors and pyranometers are linked to the ULM-500. PAR sensors measure the flux of quanta (unit, μmol m-2 s-1) in the photosynthetically relevant wavelength range, that is, between 400 and 700 nm. Pyranometers detect the power of radiation (unit, W m-2) mostly in a wider spectral range so that solar radiation arriving at the Earth’s surface can be measured. When power of radiation is measured, a flux of short-wavelength (e.g. blue) photon results in a higher signal than the same flux of photons with longer wavelengths (e.g. red) simply because the former flux carries more energy than the latter.

The higher energy in blue than in red photons, however, is unavailable for photosynthesis so that photon fluxes as they are measured by PAR sensors are important for photosynthetic studies. We offer three different PAR-sensors suitable for use in conjunction with the ULM-500.

Dynamic Range

The ULM-500 has 5 sensitivity ranges with fast automatic switching. As a result it has a high dynamic range reaching up to 99 999 μmol m-2 s-1 and may detect signals down to 0.1 μmol m-2 s-1 – even with the smallest sensor we offer. The range-switching can be set to automatic for convenient measurements or to manual for fast time resolution.

Design: Light grey plastic housing with connectors, membrane keyboard and a white illuminated LCD graphic display

Dimensions: 12 x 7.5 x 3.5 cm

Weight: 210 g (including 4 AAA 1.5 V batteries)

Power supply: 4 AAA-type batteries or 5 V DC from USB voltage source when connected to the computer

Working conditions: 35 to 85 % rH (avoid condensation), - 20° to + 50°C ambient temperature

Time resolution: PAR channel #1: 100 samples / second, PAR channel #2 and other channels: 5 samples / second

Operation time: 10 days or ca. 100 days automated logging with sleep mode (1 meas. / 5 min). Unlimited working time via USB connection (PC-software WinControl-3 – no sleep mode)