VH400 Economic Soil Moisture Sensor

Economic Soil Moisture Sensor Probe - VH400
All of Vegetronix soil moisture sensors have the following properties:
Low cost
Low power
Durable
High accuracy
Small size
Insensitive to salt.
Regulated input voltage
Wide input voltage range

Note: VH400 model is compatible with HOBO U12 loggers only by using the specially designes SSE Electronics. It is also directly compatible with the analog channels of the HOBO U30 and H22  loggers and stations, and the GP2 Data Logger from Delta-T.

The VH400 has a narrow sensing range, and only senses in the immediate proximity, and so is insensitive to differences in the volume of the medium being measured.

If the probe is going to be buried or if the probe is going to be used to measure pots of differing volumes then the VH400 should be used.

Use the VH400 soil moisture sensors in soils where the soil will have higher water saturation.
Use the VH400 where you need an absolute moisture measurement that is independent of volume, as in the case of measuring moisture in potted plants.

 See Video: Soil Moisture Sensor as Water Level Sensor

The Techno Gardener demonstrates how a Vegetronix soil moisture sensor can be used as a water level sensor. 

See Video: How To Wire Up a Soil Moisture Sensor

 The Techno Gardener shows you how to wire up a Vegetronix soil moisture sensor to a digital multimeter.

VH400 Piecewise Curve

Most curves can be approximated with linear segments of the form:

y= mx-b,

where m is the slope of the line

The VH400's Voltage to VWC curve can be approximated with 4 segents of the form:

VWC= mV-b

m= (VWC2 - VWC1)/(V2-V1)

After m is determined, the y-axis intercept coefficient b can be found by inserting one of the end points into the equation:

b= mv-VWC

Soil Moisture Sensor VH400 Wiring Table:

Some Data Loggers of this list may require the use of the SSE Anticipator with the VH400 Sensor.