The instrument behind every PAR figure published on this site. It measures photosynthetic photon flux density underwater.
Why I chose it
Purchased because inexpensive PAR meters vary significantly. The goal was repeatable measurements using an instrument trusted in horticulture research, with an underwater sensor and a spectral correction intended for use below the surface.
What I've learned
·Underwater readings differ enough from above-water assumptions that only in-water measurement is used on this project.
·Holding the sensor level matters, because small tilts change the reading. Position and orientation are kept consistent between surveys.
·Repeating the same twenty positions makes fixture changes comparable rather than anecdotal.
Installation
Not installed. Hand-held and submerged for each reading, then removed.
Configuration
·Underwater quantum sensor, measuring PPFD in µmol/m²/s
·Twenty repeatable positions corresponding to plant groups
·Measured mid-photoperiod with room lighting minimized
·Readings logged by hand against plant position and depth
Maintenance
·Rinse and dry the sensor after each survey.
·Store with the cable loosely coiled to avoid stressing the entry point.
Known limitations
·Hand-held use means position and orientation repeat only to the precision a hand allows.
·Only the factory calibration stands behind absolute accuracy; no independent reference has been used here.
·A quantum sensor measures photons on its plane and says nothing about spectrum.
Calibration
Factory-calibrated. Readings are taken at fixed positions and orientation so surveys stay comparable to each other, which is what matters for a before-and-after comparison.
Current observations
·Used for the standing twenty-position survey and re-run after any change to the fixture.
What this item is doing now, as distinct from what has been learned over time.
Live measurements
Positions measured
20
Measured range
50–176 µmol/m²/s
Read from this device on the overview page.
Maintenance history
No service dates recorded yet. Scheduled replacement applies to consumables; this item is tracked by condition instead.