Product Manual

Rod Length Water

8 inches (20 cm) 60 - 65%

4.8 inches (12 cm) 70 - 75%

3 inches (7.5 cm) 75 - 80%

1.5 inches (3.8 cm) 65 - 70%

Note: The meter does not read 100% in water because the soil moisture

calibration equations were created to be most accurate in the volumetric

water contents typically found in mineral soils.

Appendix 2

Checking VWC Readings

There are two tests that can be performed to check if the meter is operat-

ing properly.

Test 1 (No rods): Disconnect the rods from the probe block. Select the

Period option for Moisture Type (p. 12). With no rods connected, the

meter should read 1930 ± 30 µs.

Test 2 (Rods attached): Readings can be taken in three standard environ-

ments; air, distilled water, and playground sand saturated with distilled

water. It is important that any troubleshooting be done with distilled wa-

ter. Readings taken in tap water can differ greatly from the expected re-

sults observed in distilled water. When readings are taken in water and

saturated sand, the container should have a diameter of at least 3 inches

(7.5cm) and should be tall enough so the rods can be completely im-

mersed or inserted.

Readings should be taken with the Soil Type set to Standard (p. 11) and

Moisture Type (p. 12) set to TDR 300 mode. Be sure that the correct

Rod Length (p. 11) is selected. The meter should read VWC=0% in air.

In saturated sand, it should read between 35% and 45%. The table below

shows the approximate ranges of volumetric water content that are ex-

pected for the different rod lengths in distilled water.