1. Aquation’s Calculators

1.1. Rapid Light Curves  – Curve Fitting

Rapid Light Curves (RLCs) generated by PAM fluorometers provide values of Electron Transport Rate (ETR), or more often relative Electron Transport Rate (rETR), vs irradiance as Phorosynthetically Active radiation (PAR). These curves can be described by numerous non-linear least squares models, with model parameters often defining key values such as the maximum ETR (ETRmax) and the initial slope of the curve (alpha).  For a more detailed description see Aquation’s guide to analysing RLCs “How to Analyse a Rapid Light Curve“.  Two Excel spreadsheets for analyzing these curves are also provided:

Parameter estimates only are calculated using Solver (download Aquation Curve fitter, no error Aug17),

Parameter estimates and error estimates using a macro that must be installed, files can be found in the folder Aquation Optimiz tool. Error associated with ETRmax of curves with a downturn or “beta” term is not provided as the calculus gets too complicated.


 1.2. Rapid Light Curves  – Actinic Light Interpolator

Older style PAM fluorometers that use halogen globes to provide actinic light suffer from changing actinic light intensity from curve to curve.  Aquation’s Light Curve Interpolator  is designed to estimate the PAR intensities of each step of subsequent light curves, where an incremental decline in intensity is propagated through a batch of curves.  This requires one to conduct a so-called “actinic light curve” at the beginning and end of a run of multiple RLCs.  The Interpolator was originally written for the Diving-PAM.

2. Ray’s Calculators

The following tools were developed by Dr Raymond J. Ritchie who has kindly allowed us to reproduce them here.  The tools offer a range of calculating functions in the form of spreadsheets, and are largely self explanatory.  Insert your parameter values and the calculator should do the rest.  You may have to upgrade your software and download the Solver function.  Feel free to download and use for your research.  Our only stipulation is that these tools not be sold for commercial gain.

2.1. Carbonate Calculator

The Ritchie Carbonate Calculator calculates the concentration of CO2, HCO3-, and CO32- in natural waters or artificial media. Required inputs: pH, Temperature, Salinity, Current atmospheric CO2 (ppm), Total alkalinity.

Download Carbonate Calculator

2.2. Dilution Calculator

The Ritchie Dilution Calculator determines the volume of Stock solution required to produce a volume of target solution.  Required inputs: Concentration and volume of the Final solution required, and the concentration of the Stock solution.  The Calculator also determines the concentration and volume of a Final solution created by mixing two solutions (with known concentrations and volumes) together.

Download Dilution Calculator (15 KB)

2.3. Irradiance  Calculator

The Ritchie Irradiance Calculator calculates by interpolation the Photosynthetic Photon Flux Density (PPFD), UV-A and UV-B  in units of micromols photons per metre squared per second, in increments of 15 minutes over the course of every day in a 365 day sequence. Calculations of irradiance in PPFD, UV-A and UV-B are also provided in units of mols per metre squared per day, and summed to provide mols per metre squared per annum.

Download Irradiance Calculator

2.4. Waiting in Line Calculator

The Ritchie Waiting in Line Calculator is used for curve fitting, typically for Light Response curves including RLCs.  The waiting in line principle was originally developed in the telephony industry and provides an excellent description of photons waiting in line to enter the electron transport chain.  Few photons, no queue; more photons, a queue forms, even more photons, the queue gets longer.

Download Waiting in Line Curve Calculator 

2.5. Chlorophyll Calculator

The Ritchie Chlorophyll Calculator.  Determines concentration of Chlorophylls a, b, c and d, using acetone, methanol, ethanol and/or diethyl ether.

Download Chlorophyll Calculator

2.6. Refraction vs. Salinity Calculator

The Ritchie Refraction vs. Salinity Calculator determines the refractive index for water of a specific salinity, and the effective light path of solar radiation at a given angle, useful for polar ocean light transmission calculations.

Download Refraction vs. Salinity Calculator

2.7. Quanta vs. Solar Elevation Calculator

The Ritchie Quanta vs. Solar Elevation calculator determines characteristics of light for various solar angles allowing for the effects of light passing through the atmosphere.  Calculates solar angle for PAR, UV-A & UV-B, and Near-IR; provides extraterrestrial irradiance at 1 AU from 280 to 1000 nm expressed as quanta m-2 s-1.

Download Quanta vs Solar Elevation Calculator

2.8. Oxygen II Calculator

The Ritchie Oxygen II Calculator determines the solubility of oxygen in water of varying salinity and temperature.  Several models are provided for your calculating pleasure.

Download Oxygen II Calculator

Raymond J. Ritchie,
Faculty of Technology and Environment,
Prince of Songkla University-Phuket,
Kathu, Phuket 83120, Thailand
E mail:,
FAX: +66 76 276 102,
Phone: +66 76 276 108.