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Delmhorst Instrument Co.
Model KS-D1
Operating Instructions
TABLE OF CONTENTS
1 Introduction
3 Figure 1
4 Figure 1A
5 Operating Procedure
5 Interpretation of the Meter Readings
6 Meter Reading Guidelines
7 Figure 3
8 How To Use Irrigation Charts
8 Installation of the Blocks
9 Where To Place Blocks
10 Depth Of Installation
10 Care of Your Meter
11 Service of Your Meter
12 Warranty
INTRODUCTION
The Delmhorst soil moisture measuring system consists of two parts: the gypsum
soil blocks (sensors) and the measuring instrument, Model KS-D1 moisture
tester. The blocks are made of gypsum cast around two concentric electrodes.
The gypsum acts as a buffer against the effect that the salts might have on the
electrical conductivity and the concentric electrodes confine the flow of current to
the interior of the block, eliminating the effects of soil conductivity.
When a block is buried in the soil it absorbs moisture from the soil or releases
moisture into the soil, until its moisture content approaches equilibrium with the
moisture content of the soil. When the block is connected to the meter, current
flows between the electrodes and the electrical resistance of the gypsum is
measured. Such readings are an indication of the moisture available to the
plants.
For irrigation purposes, the water of importance is that amount which can be
extracted from the soil by the roots of the plants, and not the percent moisture
content (which is related to the weight of the soil). We refer to this reservoir of
moisture as “available moisture.”
Each soil has a different capacity to hold water, depending on its structure and
texture. The maximum amount of water available to the plants (called Field
Capacity) is the amount held by the soil against drainage by gravity. When
