temperature & humidity

VP-4 / ATMOS-14 digital sensor


Continuously monitor temperature, relative humidity, vapour pressure and barometric pressure, all in one sensor, with the VP-4, also known as the ATMOS-14.

The ATMOS-14 is a digital, SDI-12 sensor that is compatible with our range of diverse data logging solutions or connect the sensor to your existing data logging system. The ATMOS-14 is ideal for Australian research and environmental monitoring because it is robust, accurate and can withstand harsh conditions for many years.

The ATMOS-14 can be inserted into a radiation shield for accurate meteorological and weather measurements.

The sensor is delivered pre-calibrated and ready to measure.


  • Low cost, high accuracy
  • IP65-rated environmental protection
  • Radiation shields with natural or forced ventilation
  • Compact, weather proof design


relative humidity and vapour pressure

The ATMOS-14 is a significant improvement on other temperature and relative humidity sensors because it can output RH and vapour pressure. These parameters describe important characteristics of the environment for evaporation, transpiration and water transport which are required for agriculture, horticulture and hydrology applications.

There are three components to vapour pressure: saturated vapour pressure, actual vapour pressure and vapour pressure deficit (VPD).

Saturation vapour pressure is the amount of water vapour that the air can hold.

Actual vapour pressure is the amount of water vapour that is actually in the air at the time of measurement.

Vapour pressure deficit is saturation vapour minus actual vapour pressure.

In evapotranspiration models, such as Penman-Monteith FAO56, saturation vapour pressure is defined es or eo and actual vapour pressure is defined as ea.

The ATMOS-14 outputs actual vapour pressure. This parameter was chosen as the output because actual vapour pressure is the vapour pressure of the atmosphere (not RH) that controls the rate of vapor phase water transport (e.g., evaporation, transpiration, and distribution of water vapour).

If you require an output of vapour pressure deficit (VPD), then the scientists at Edaphic Scientific can provide this parameter in the ES-SYS data logging system or we can assist you in programming this parameter into your existing data acquisition system.

As an aside, it is interesting to note that saturation vapour pressure is increasing as global temperatures increase. However, scientists have observed that actual vapour pressure has not been increasing at the same rate. Therefore, global vapour pressure deficit, VPD, has been increasing and is expected to increase with global warming. The drier atmosphere will increase rates of evaporation and transpiration as well as affecting other hydrological processes as well as photosynthesis and carbon cycles (Grossiord et al 2020).


whole system monitoring solutions

Edaphic Scientific is a one-stop shop for a whole system monitoring solution. We provide plant and soil monitoring systems for researchers and growers.

Our systems not only support dendrometers, but related sensors such as sap flow, soil moisture, weather parameters, and more.

At Edaphic Scientific we want to work with you from the start of your project through to its completion. We can provide:

  • Assistance with project and experimental design
  • Procurement of all monitoring equipment, including sensors, data loggers and data management software. Edaphic Scientific is a one-stop shop where we can source and find any necessary equipment for your project from our preferred suppliers or third party suppliers
  • Installation and training
  • On-going assistance with data interpretation and equipment maintenance
  • Data correction and analysis, including statistical analysis with the R-package
  • Report and publication preparation including tables, figures, graphs, and manuscript writing


advanced data collection and management solutions

Edaphic Scientific recognises the need for flexible and adaptable sensor and data logging solutions for experimental or environmental monitoring projects.

Data can be downloaded directly in the field from data loggers. A direct connection between the data loggers and your computer, via a USB cable, can be used for manual downloading of data.

Alternatively, data can be downloaded over the internet on your iPhone, iPad or desktop computer with the Eagle.io cloud-based, data management software solutions. Through this remote based downloading capabilities, you can download, view and manage your data, and system, anywhere in the world and at anytime.



feature specification
relative humidity
Measurement Range 0 to 100% RH
Measurement Accuracy Temperature and RH dependent | 2 to 5 %
Response Time (τ, 63%): < 40 s
Hysteresis < 1% RH typical
Signal Drift < 0.5% RH/year typical
Measurement Range -40 °C to 80 °C
Measurement Resolution 0.1 °C
Measurement Accuracy 0.5 °C
Response Time < 400 s
Signal Drift < 0.04 °C / year typical
vapour pressure deficit (VPD)
Measurement Resolution 0.01 kPa
Measurement Accuracy 0.07 kPa at 20 °C
barometric pressure
Measurement Range 49 to 109 kPa
Measurement Resolution 0.01 kPa
Measurement Accuracy 0.4 kPa
general specifications
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 Time 300 ms
Output 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 Any SDI-12 enabled data logger

manual & docs

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