The Otto family of above ground soil moisture probes are installed into a slightly oversized hole, and bedded into a slurry.





Materials Required:
- Installation auger: T-handle, 1m bar, 35mm auger (additional 0.5 or 1m extension bars may be required for longer probes)
- 10 litre bucket
- sieve
- hand trowel
- 10 litres water
- tarpaulin or plastic sheet
- packet of zip lock bags.


Preparing the probe


Above Ground Probe:
- unscrew the cap from the probe head
- disconnect the 3 wires from the probe cable, loosen the cable gland and remove the
robe cable
- withdraw the probe internals from the probe tube and set it aside where it will not be damaged




Sub Surface Probe:
- the sub surface probe requires no preparation.


Preparing hole


Using   insulation tape, mark the installation auger to the required depth:
- above ground probes: measure the length of the probe from the bottom of the probe read to the end of bottom stopper plus an extra 3cm
- below ground probes: measure the length of the probe from the cap to  the bottom stopper plus an extra 3cm plus the depth below ground the  probe will be installed
Now drill the hole to the required depth. You will have to remove the auger every 10cm or so to clean the flutes. As you do so, lay the soil out on the tarpaulin. Take note of the changes in soil texture and record the  depths at which they occur. Set aside a sample of the soil from each  layer and place it in a zip lock bag.
Once the hole is finished, pour in enough water to fill the hole to the  surface, then allow the water to infiltrate into the soil. This will  help ensure that the moisture in the slurry is not immediately sucked  out into the soil once the slurry is poured in.


Preparing Slurry


Once you have set aside the samples from each depth, sieve the remaining soil to get rid of any organic matter or rocks
- mix the soil with water until it reaches the consistency of thick cream.


Installing probe


Pour slurry into the hole until it is filled to about 10cm below the surface
- now push the probe into the slurry to the required depth
- if you can not push the probe down to the correct depth, pull it out  again and use the auger to remove the slurry. Wet the hole up again,  then re-mix the slurry and try the installation again.


Cable Considerations




When installing probes you should always pay attention to providing adequate protection to the probe cable.
Above ground probes:
- ensure there is no slack cable on the ground which could get caught up in passing machinery
- always leave a goose-neck of cable at the base of the telemetry equipment / logger just in case the cable gets snagged.
Sub surface probes:
- after installing the probe, make a trench to hold the probe cable
- take the cable 100 to 150mm past the probe, then loop it back again.  The goose-neck created in this fashion will give you a reserve of cable  to cope with subsidence of the ground
- at the telemetry equipment / data logger end, leave a loop of cable  loosely cable tied to the post. If anything snags the cable, this will  act as a buffer hopefully avoiding cable damage