These are Tensiometers for manual use. They are simple, reliable, inexpensive devices for local readings. The vacuum gauge installed at the top, shows the soil water tension value.
Structure and principles of operation:
The tensiometer consists of a PVC tube, with a transparent part (the control window) at the top and a porous ceramic cap at the bottom. A clock shaped, mechanical vacuum gauge, is screwed on the top. Ami tens' standard gauge consists of a G1/4" back thread and a special adaptor with a rubber seal that prevents vacuum lost from the device. In order to fill-up the tube with water the gauge is removed through its adaptor and installed manually and firmly after refill.
The tensiometer is installed into the root zone to create a good contact with the ceramic tip and the soil water. When the soil is drying the water tension gets bigger and vacuum power in the pipe is rising and displayed by the gauge. Our standard gauge displays the vacuum power in Centibars or Millibars (Depends on the model)
Following rain or irrigation the tension gets lower. By following the results continuously, the user can get the right decision when and how much to irrigate for best results.
Gauges thread configuration:
The models we supply, consists of a G1/4" thread, in 2 configurations:
1) Back thread for top installation. This is our standard type.
2) Bottom thread (for side installation), supplied only for special orders.
Gauges reading options:
Our standard gauges scale is in Centibars (equal to Kpa)
Available ranges: 0-100 CB or 0-60 (only for special orders)
Low tension models are used for artificial media or rough sand, with low water capacity, where the users need to detect small tension changes and start irrigation cycles at low values. The scale of these models is in Millibars (MB)
Available ranges: 0-250 MB / 0-100 MB (nonstandard)
Each of these gauges also include a calibration screw to delete the vacuum value, created by the pipe's length.
For Tube's configuration, allocation and data interpretation, please read the relevant chapters on Tensiometers General page.
Yet, one important tip for Mechanical tensiometers is the need of a daily follow up of results in order to study the on-going changes of water content in the soil and react accordingly.