Testing soils with pH meter

Before testing

  • Always calibrate the meter every time before testing
  • Mix soil and water well and leave 10 to 20 minutes to ensure consistency of results
  • Wash the probe between each soil sample to prevent cross contamination between samples.
  • Soil pH meter readings should never be used for lime recommendations. Lime advice should only be based on a laboratory soil test result for consistency of results and to avoid over estimation of soil pH.

………......

Testing a soil sample

  1. Remove cap and press on/off button to turn on the tester
  1. Take a level scoop of soil & place in a clean container
  1. Add an equal volume of distilled water
  1. Stir / shake for a few minutes
  1. Leave stand for 15 - 20 minutes. Stir / shake again before testing
  1. Insert pH meter & stir once and let the reading stabilize.
  1. Note the pH value. Press hold/ent button to hold (HO) the reading. Annunciator will flash to indicate reading is in hold mode. Press hold/ent again to cancel (HC) the hold mode.
  1. Wash the probe between each soil sample with distilled water in wash bottle.
  1. Once finished press the on/off button to shut tester off.
  1. Place the probe in storage solution provided to maintain / condition the meter probe.

Setting up pH meter

1.Conditioning

Condition the tester before first use. Remove the transparent cap and fill with tap water to a height of 20 mm. Recap the tester and soak* sensor for one hour. This will activate the sensor and dissolve any crystals present. Rinse the cap after use. If the electrode has dried out (during storage) re-wet/soak in storage solution for 24hrs. Before calibration immerse sensor in buffer pH 7.0 for 20 minutes to prime electrode.

2.Calibration

  1. This tester allows up to 3-point calibration. Start with pH 7.0 buffer
  1. Press on/off button to power on.
  1. Immerse sensor in about 20 mm of buffer and stir gently
  1. Wait for displayed value to stabilize at or near pH 7.0
  1. Press cal button to enter calibration sequence. CAL will flash momentarily and then show a flashing default reading.
  1. To complete the first calibration point, press hold/ent button to confirm (Ent).
  1. Proceed to next buffer value (pH 4.0) and repeat the calibration procedure to obtain your second calibration point. Buffers 4 & 7 should be adequate for calibration & testing soils.
  1. To abort calibration, press cal button to escape (ESC). (Restart calibration)
  1. You have successfully calibrated the instrument.

3.Maintenance

  1. Rinse the sensor in tap water after use.
  1. In harsh samples, take readings quickly, then rinse sensor immediately afterwards with de-ionized water to remove residues and prevent electrode contamination.
  1. For long-term storage, fill the cap with 20 mm of storage solution (NOT de-ionized water), and replace cap*. This will keep the sensor conditioned and ready for next use.

Notes:

* The tester cap is not leak-proof. Please keep tester upright

If no button is pressed for 15 seconds, tester will automatically confirm calibration.

Tester automatically shuts off after 8.5 minutes of non-use to conserve batteries.

Prepared by: - Mark Plunkett, January 2014