Using the Bluelab Guardian Monitor
Check out the One Stop Grow Shop Blog to find out how to get pH right in hydroponics. You'll also find information on calibration and the availability of nutrients at different pH ranges. To learn how to control nutrient strength, see the following article.
Before doing anything, you should soak the pH probe in KCL (potassium chloride) solution for 24 hours. This is very important!
The Bluelab Guardian can be mounted in a suitable area, using the 4 supplied screws. Make sure that it is placed in an area that will allow the probes to reach the reservoir tank comfortably – no further than two meters away. Two cable ties are supplied with the unit, which can be used to mount it to a support or hanging bar. Avoid positioning the Guardian in areas of direct sunlight. Though the unit is water resistant, you should also avoid positioning it in areas where it can easily be splashed with nutrients. Mineral salt deposits can be corrosive and cause damage over long periods of time.
Choose the correct plug adapter from the supplied selection, connect it to the Guardian's power supply, then connect the power supply to the underside of the main unit. Attach the pH probe to the underside of the unit, by inserting and twisting. The temperature / conductivity probe is supplied pre-attached. The unit can now be powered up at the mains supply.
To select your desired conductivity unit, hold the unit button, located next to the conductivity display, down for 3 seconds. This process will trigger a move to the next unit of measurement, as indicated by the 3 LEDs to the right of the display. Repeat this process until you have arrived at your chosen unit of measurement. Repeat the whole process again for your choice of temperature measurement.
The conductivity / temperature probe is supplied factory calibrated and will only require periodical cleaning. The pH probe, however, will need to be calibrated before use. Add a small amount of pH 7.0 calibration solution to a small beaker or plastic container, dip the end of the probe in the solution and hold the 'pH cal' button, located to the left of the pH read-out display. Rinse the probe tip and repeat the process with either pH 4.0 or pH 10.0 solution to provide a more accurate calibration.
Long-term, the two pH LEDs located to the right of the pH read-out display will keep you informed of the pH calibration status. Consult the full instruction manual for full details on the different statuses. Effectively, if both LEDs are not lit permanently then calibration of some form is required.
The two probes can then be placed in the reservoir tank. Fit the included suction cup holder to the pH probe by gently pushing it over the tip and twisting it round the stem. The probe can now be stuck to the side of the reservoir, preventing it from damage when stirring solutions, etc. The conductivity / temperature probe is less delicate and can be placed straight into the nutrient reservoir.
The alarm function will warn you with a flashing LED when readings drop below, or rise above, a pre-determined value. To set the alarm hold the alarm button until the letters 'AL H' are displayed in each of the three display windows. As soon as you take your finger off the button, the current highest values will be displayed in the three windows. Use the unit buttons to select which parameter you wish to adjust and then use the up and down buttons to lower or increase the each maximum parameter value. Remember that you are setting the highest acceptable value. If levels go above this, then the visual alarm will start to flash. Once you've set the high values, press the alarm button to move onto the low values and repeat the process. Press the alarm button again and your chosen parameters will be saved.
Always take great care with the pH probe. Under no circumstances should you ever allow it to dry out – when not in use, replace the storage cap.