CABLE AND CABLE STOPS
The 503 DR Hydroprobe comes with a cable 12 feet long and 5 cable stops.
If you need more cable stops, you can order them from the manufacturer.
The cable and cable stops are shown in the picture at the right. The black
arrow is pointing to a cable stop. One end of the cable is connected to
the probe and the other end is connected to the control unit. When you
measure the soil moisture with the neutron probe, lower the probe by letting
the cable connected to the probe down little by little. You stop the cable
and hold the probe in the desired position by an attached cable stop holder.
There are five cable stops, which allows you to measure 5 depths. Fig. 5 shows the cross section of the gage. Since the measurement point of the probe is 13.6 cm above the bottom line of the gage when the probe is in standard position, the first cable stop should be placed at the point that the cable length before the first cable stop equals (13.6 + height of gage base above the ground + the first desired depth cm). For example, the gage is 10 cm above the ground, and the first depth desired is 30 cm, then the first cable stop should be placed at (13.6 + 10 + 30) = 53.6 cm. Then the other cable stops should be placed at points that increase the cable length by one unit increments (e.g. 30 cm) from the previous cable stop. The cable stop positions need to be checked at the beginning of each growing season.
The Neutron Probe
StandYou can make a neutron probe stand as shown in fig. 6. It is a short pipe with a little wider diameter than the access pipes. (The picture below shows a neutron probe sitting on a stand about 30 cm high.) Using a neutron probe stand has two advantages: one is to lift the gage high above the soil ground, so that it will not be affected by the soil ground surface condition; the other is that it makes the height of the gage from the ground consistent. It will not be affected by the height of the access pipe above the ground. Because the heights of the access pipes above the ground may be different, if you do not have a stand, every time you get to a pipe, you will need to make adjustments in your depth calculations to account for the differences. With the neutron probe stand, the height of the gage is always the same, [the length of the stand], regardless of which pipe you are at. Therefore, you only need to set the cable stops once, and use the stand whenever you use the neutron probe.
* Special Thanks to Dr. Ron Sorenson for providing the innovative idea
and prototype neutron probe stand.
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