How does a soil pH meter work?

A soil pH meter is a handy little gadget that will let you know just how acidic your soil actually is.

In fact, knowing your soil acidity levels when looking at making adjustments to its pH is vital. This is because an increase of 1 on a soil pH meter translates to 10 times the acidity of the soil in chemistry terms and will directly affect your planting and growing capabilities in your garden.

A pH meter relies on a voltage test to determine hydrogen ion levels and thus pH.The more hydrogen ions in a solution, the more conductive it will be. So the more acidic a solution, the more electricity it will conduct. This is what the pH meter relies on.

In order for electricity to flow around a circuit, it must be complete. A pH tester circuit is completed by the test sample. The sample soil comes into contact with two electrodes which are found on the probe.

An electrode is a part of a circuit which comes into contact with non-metallic elements. The electrons travelling around the circuit are attracted to the electrodes’ membrane.pH meters have two electrodes, a glass electrode and a reference electrode. The glass electrode has a permeable membrane made from specialised glass, which houses a chemical solution and a silver-based wire. The reference electrode is also made up of a wire in a chemical solution.

The reference electrode is stable and works as a buffer and a reference against which the other electrode can be compared, and the pH determined.The glass electrode attracts the hydrogen ions. This then creates a small voltage which can be compared to the reference electrode.

The voltage difference between the two electrodes is then sent as a signal to the indicator, which is translated into a pH reading.For analogue pH meters this signal acts upon an electromagnetic coil which causes the needle to rotate about its hinge and give a pH reading on the scale.Digital pH meters require an analogue-to-digital converter to produce the number displayed on the LCD screen.

The reference electrode is calibrated before the devices are sold, which means it is set at a certain pH (generally 6.86 – close to neutral). Calibration is usually set using a buffer solution with a known pH, which the device can then be altered to.

Most basic soil pH meters cannot be calibrated after purchase. However, they can be placed in a buffer solution to check the device is indicating correctly. Buffer solutions are not widely available and can cost more than the meter itself, so this test is not usually deemed necessary.

pH meter results may be affected by temperature, but pH itself is temperature-dependent and so the results are a true reflection of these changes. However, the probes may also have slight discrepancies determined by temperature. These will be minimal but should be considered if an unexplained change occurs.

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How do you use a soil Ph meter?

1.Clean the prongs of the tester with distilled water and a clean cloth before use, and between uses. This will keep the readings from being affected by the pH of a previous test or tap water.

2.Insert the prongs into the soil you wish to measure. The first reading that appears will be a pH, which is measured on a scale from 1 to 14, with 1 being the most acidic and 14 being the most alkaline. Seven is a neutral pH. Most plants will grow in a pH between 6 and 7.5. The soil tester measures pH levels from 3.5 to 8. Alter soil pH by adding limestone to raise it, or sulfur to lower it.

3. Press the button on the tester to view the moisture readings. The tester measures the percentage of moisture content in 10 percent increments, from no moisture to complete saturation. Most plants will want moist soil in the mid-range. Sand can be added to soil to increase drainage capabilities for excessively wet soil.

4.Press the button on the tester again to view the light readings. Light readings measure light intensity in foot-candles from 0 to 2,000. For reference, average indoor home lighting is around 100 foot-candles. Plants requiring full sun can be planted in the upper light ranges, and plants requiring shade can be planted in the lower light areas.

Which Soil PH Meter Should You Buy?

The accuracy of soil pH meters and testing kits varies, but not by much. The choice you make will come down to how much you want to spend, how often you intend to test, and how easy you want it to be. While an electronic meter will provide the best accuracy, which registers to the nearest decimal point, it may be an expensive purchase and more than a general gardener would require.

If you are looking for a rough guide to the acidity of your garden soil purely for planting purposes, then the Dye & Test strips will suffice. However, if you are looking at changing or increasing your soil pH via the use of soil additives, then you really need an electronic meter to prevent your garden becoming overly acidic and leading to plant death.

Try to work out how often you intend to test your soil pH level, how much you want to splash out on a tester, and whether you need detailed information or just a rough estimate of acidity levels. Hopefully, this article will help you make up your mind and see how accurate are soil pH meters are for your garden needs.