EnviroDIY

2024-11-05 at 3:40 PM #18725

Moderator

That all looks correct. I usually put the Mayfly’s analog Grove jack voltage selector jumper to the 5v position because the old sensors required 5v for excitation, but supposedly these newer ones are happy with 3v to 15v, but we still use them at 5v and calibrate them with that excitation voltage. If you connect the 6-pin screw terminal board shown in your photo to the Mayfly’s upper aux analog jack (AA0-AA1), then your sensor will be connected to the A0 pin, so make sure that’s what you’ve entered on the line of your sketch that looks like this:

const int8_t cyclopsChloroADSChannel = 0; // ADS channel

We’ve only used the C-FLUOR sensors for phycocyanin but I would assume their operation and performance would be the same for the chlorophyll model. Which one are you using? The ModularSensors library for the Cyclops sensors assumes you’ll be entering the two voltages of the sensor output (blanking voltage and standard concentration voltage), and the concentration of the standard. So for my station, it looks like this:

// Cyclops calibration information
const float cyclopsChloroStdConc = 40.000; // Concentration of the standard used
                                          // for a 1-point sensor calibration.

const float cyclopsChloroStdVolt = 1.155488; // The voltage (in volts) measured for the conc_std.
const float cyclopsChloroBlankVolt = 0.020348; // The voltage (in volts) measured for a blank.

// Cyclops calibration information

const float cyclopsChloroStdConc = 40.000; // Concentration of the standard used

// for a 1-point sensor calibration.

const float cyclopsChloroStdVolt = 1.155488; // The voltage (in volts) measured for the conc_std.

const float cyclopsChloroBlankVolt = 0.020348; // The voltage (in volts) measured for a blank.

These voltages were obtained by placing the sensor (with power applied) in nanopure water (or distilled if that’s all you’ve got) in a large dark contained (a black opaque 1-liter bottle) and measuring the output voltage of the sensor. Then we repeat it with 1 liter of the standard (the Rhodamine standard purchased from Turner). If you’re measuring the voltage with an external voltmeter, remember that you’ll need to divide the voltmeter voltage by 2 because you’ve got that resistor-divider circuit on your screw terminal board. So if you put the sensor in the standard and get 2.2 volts, you would then enter 1.1 volts into the sketch. Same thing for the blanking voltage (although it’s usually a really small number closer to zero.) We usually measure the voltage out to 5 decimal places using the Mayfly to measure the analog voltage 100 times (20 milliseconds apart) and take an average, then do that at least 50 more times, and take an average of all those measurements.

If you’ll be entering the data from the sensor’s calibration sheet instead, you’ll need to enter blanking voltage from the sheet (again, dividing by 2 because of the res-div). So let’s pretend the datasheet says the blanking offset is 0.02 volts, so divide that by 2 and get 0.01. And then the sheet gives you the calibration coefficient as ppb per volt (parts per billion per volt). So pretend a sensor’s datasheet said 1035.4234 ppb/v. So you could enter that number in the concentration line and 0.5v for the voltage (because that’s half of one volt), like this:

const float cyclopsPhycoStdConc = 1035.4234; // Concentration of the standard used
                                         // for a 1-point sensor calibration.
const float cyclopsPhycoStdVolt =    0.5; // The voltage (in volts) measured for the conc_std.
const float cyclopsPhycoBlankVolt =    0.01; // The voltage (in volts) measured for a blank.

const float cyclopsPhycoStdConc = 1035.4234; // Concentration of the standard used

// for a 1-point sensor calibration.

const float cyclopsPhycoStdVolt = 0.5; // The voltage (in volts) measured for the conc_std.

const float cyclopsPhycoBlankVolt = 0.01; // The voltage (in volts) measured for a blank.