For some time I have been manually logging various parameters associated with my aquarium; pH, temperature and CO2 flow-rate. I have become very bored with the daily grind and wish to automate the whole process. The DrDAQ looks like a very good step in the right direction, but I have problem with how to log the CO2 flow-rate.
Currently, there is a "bubble-counter" fitted in the CO2 line. It lets me see, and sometimes hear, bubbles of CO2 as they are forced through a small, water filled bottle. I simply measure the period between these bubbles to obtain an uncalibrated flow-rate.
Do you have any ideas about how I might make a similar measurement using Pico technology?
The pH is obviously taken care of via the DrDaq's pH input. However flow is a little more complicated. You will need to source a suitable flow sensor with a voltage output. The sensor should give a voltage out proportional to the flow rate. The DrDaq's voltage input could then take care of the flow measurement.
Unfortunatley, we do not stock any flow sensors. A good place to source a suitable sensor would be http://www.sensorland.com
I hunted around for applicable flow sensors. Unfortunately, my requirements are rather awkward - the basic problem being a very small flow rate.
At some point I gave up the search and decided to make one myself. If I may say so myself, I am quite pleased with the results. It uses an IR detector and emitter to spot gas bubbles in a small water-filled container, and an Atmel microcontroller to do the measurements and a degree of signal filtering. Finally it uses a DAC and op-amp to provide the voltage required by the DrDAQ. Because of the resultant high current requirements, a mains adapter provides a parallel power supply.
Having got this far, I finally commited myself to buying the DrDAQ itself. It's an excellent piece of kit and does everything I want, except I cannot get it to recognise my sensor.
Last night I tried a using simple dummy sensor built from a 2K2 resistor and a 100K pot. Even this didn't seem to be recognised by PicoScope (5.08). The calibration file (bubbpers.dds) looks something like this:
When I try to use either my bubble sensor or the dummy, the Y-axis of the scope appears without the correct label and a simple 0 to 100 range. Can you help?
This worked fine on Ext1 so we know there's no problem with the software. Perhaps your sensing resistor is the wrong value? ... it should be connect between pins 2 and 3.
The voltage input should be between pins 1(+ve) and 2(ground).