For quick reference, here’s the Official Meter Guide from Blumat Austria.
Without further ado, here’s the:
Sustainable Village Guide to the Blumat Digital Moisture Meter
The Blumat Digital Moisture Meter is a great tool for any gardener. While I typically recommend it to first-time Blumat system users to ease the learning curve, it can be useful for cultivators with any irrigation system. The meter displays exactly how much moisture is in your growing medium. This is displayed in terms of mbar.
Mbar is a unit of pressure measurement. The digital meter uses the same technology as a tropf Blumat to measure pressure differences in your medium, and displays that measurement digitally.
The meter is composed of three parts:
1) Digital Display:
2) Extension & Ceramic Sensor:
3) Recommended Protective Silicone Cap (Included on sustainablevillage.com orders):
How It Works
The ceramic extension is soaked in and filled with water, just like a Blumat sensor. When this is inserted into growing medium, the medium exerts a pressure on the water inside the cone. When the medium is more dry, it pulls harder on the water inside the cone. When the medium is more moist, the force pulling inside the cone is less. These forces of pressure correlate to different readings on the meter. A reading of 0 indicates standard water, while a high reading of 750 or so indicates sawdust completely void of moisture. The digital moisture meter is a tensiometer, but indicates moisture levels using pressure as a correlative.
How to Use
- Water medium the night before you intend to install the meter. Follow up the morning after. The goal is to get medium to a moisture level that your plants seem happy with–prior to using the meter.
- Separate the three meter components.
- The ceramic cone and plastic extension should be soaked in water for at least 15 minutes. This ensures the pores of the ceramic will be saturated with moisture.
- While the digital display is disconnected, hold the on button for 3 seconds or so. The display should read “000.” Wait a moment, then screw the display onto the pre-soaked and water-filled ceramic/plastic extension. Unlike Tropf Blumat Sensors, it is not imperative that the extension is completely void of air/gases.
- Insert the meter into your medium. Wait 20-45 minutes.
- Push the button, and the meter should be displaying an accurate measurement in terms of mbar. Depending on environmental factors, you’ll want different readings. In living soil, depending on conditions, growth stage, etc., I aim for 80-160mbar at any given time.
- The meter can be moved and re-situated to get readings at various places in a garden. Once it is moved to a new spot, it needs another 20-45 minutes or so to get an accurate reading.
Over time, the meter will begin displaying inaccurate readings. This will be fairly obvious. In soil that seems healthy, you might get readings of several hundred mbar. Don’t be alarmed! The meter has probably voided of water.
If this is the case, here is the re-calibration procedure:
- Unscrew the digital display from the ceramic cone.
- Soak the ceramic cone in water for 15 minutes.
- Remove cone from water while keeping the cone full of water.
- Hold the on-button for 3 seconds until “000” is displayed.
- Screw the digital display back onto the cone.
- Insert meter into growing medium. Wait 20-45 minutes.
- Push on button, and observe the digital display.
Changing the Battery:
- Using a small Phillips head screwdriver you can unscrew the two plastic halves.
- Replace the old battery with a new battery (purchase here).
- Wait until after watering media to let the moisture evenly disperse and stabilize before trusting readings from the meter.
- Aim for 100mbar on average in living soil. Some gardeners report best results at 40mbar–I personally get overwatering symptoms there. Let mbar readings on your meter be a guide to plant health, not a tyranny that rules your mental peace.
- The meter cannot be used in extremely airy or chunky media such as chunky perlite, lava rock, etc. When the ceramic is in contact with air, the pressure readings will be extremely high. However, your plant roots may have access to moisture in these media even when the meter is displaying high readings.
- Avoid getting the digital display wet. The silicone cap is highly encouraged in all circumstances, and is completely necessary for outdoor growers as well as those who supplement with any over-the-top watering.
- Do not drop or otherwise rattle the display.
- Keep the digital display in dry storage when it’s not in use.
- If the meter is not performing as it should, and you’ve attempted the re-calibration procedure recommended above, you can also try to reposition the meter in the soil.