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Enabling better global research outcomes in soil, plant & environmental monitoring.

Decagon VP-4 Temp & Humidity

Relative Humidity, Barometric Pressure, Air Temperature, and Vapor Pressure with or without a passive radiation shield.

Use the rugged VP-4 sensor with soil moisture probes in microclimate and evapotranspiration studies

RELATIVE HUMIDITY
RANGE 0 to 100% RH
ACCURACY Sensor measurement accuracy is variable across a range of temperatures.
Refer to the chart in Figure 1 to determine the accuracy specification for the VP-4 sensor.
EQUILIBRATION TIME
(τ, 63%):
< 40 s (response time in 1 m/s air stream)
HYSTERESIS < 1% RH typical
LONG TERM DRIFT < 0.5% RH/year typical
TEMPERATURE
RANGE -40°C to 80°C
RESOLUTION 0.1°C
ACCURACY Sensor measurement accuracy is variable across a range of temperatures. Refer to the chart in Figure 2 to determine the accuracy specification for the VP-4 sensor
EQUILIBRATION TIME
(Τ, 63%)
< 400 s (response time in 1 m/s air stream)
LONG TERM DRIFT < 0.04°C / year typical
VAPOUR PRESSURE
RANGE 0 to 47 kPa
RESOLUTION 0.01 kPa
ACCURACY Sensor measurement accuracy is variable across a range of temperatures and RH. Refer to the chart in Figure 3 to determine the accuracy specification for the VP-4 sensor.
BAROMETRIC PRESSURE
RANGE 49 to 109 kPa
RESOLUTION 0.01 kPa
ACCURACY 0.4 kPa
GENERAL
DIMENSIONS 1.96 cm (dia) x 5.4 cm (h)
POWER REQUIREMENTS 3.6 to 15 VDC, 0.03 mA quiescent, 4 mA during 300 ms measurement
RESPONSE (MEASUREMENT) TIME 300 ms
OUTPUT Decagon Digital or SDI-12
OPERATING TEMPERATURE -40°C to 80°C
CONNECTOR TYPES 3.5 mm (stereo) plug or stripped and tinned lead wires (pigtail)
CABLE LENGTH 5 m standard; custom cable length available upon request
DATA LOGGER COMPATIBILITY
(NOT EXCLUSIVE)
Decagon: Em50 Series (Firmware 2.19+)
ICT SDI-12 logger, AML, AWS, Universal Telemetry Hub
Campbell Scientific: Any logger with serial I/O
HANDHELD READER COMPATIBILITY ProCheck (rev 1.57+)
SOFTWARE COMPATIBILITY ECH2O Utility (rev 1.74)​
DataTrac (rev 3.11+)

VP4 Humidity Acc

VP4 VP Acc

Temperature Acc VP4

SDI-12 Compatible

Integrate into non-Decagon data loggers with the easy-to-use SDI-12 communication protocol.

Compact

This 5 cm x 2 cm sensor is able to fit into the smallest of spaces.

Weatherproof

Thanks to its unique Teflon screen, the relative humidity sensor can survive a deluge. Naturally, it won’t be transmitting accurately while waterlogged; but as soon as it has dried out, it’s back in the game.

Fast Response

The Teflon screen protects the sensor from liquid water and dust without limiting diffusion of water vapor. The protected sensor is still able to quickly respond to changes in humidity.

Integrated Temperature for Accuracy

Accurate relative humidity readings require accurate air temperature readings taken at the same place and time. This sensor takes both measurements simultaneously for the best possible accuracy.

Radiation Shield Included

The included radiation shield is designed to improve air temperature readings by minimizing radiation and maximizing airflow over the surface of the sensor. Specially designed to preserve the correlation between actual air temperature and sensor air temperature while keeping the shield size small.