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

PSY1 Leaf Psychrometer

The leaf psychrometer follows the same principle of measurement as the stem psychrometer, however the body of the chamber is reduced to accommodate smaller and thinner leaf areas in several plant species. The technique used to prepare and install this instrument has also changed as it requires additional care to prepare the installation site. The leaf psychrometer measures the water potential (water status) on a leaf of a plant. The leaf water potential is a quantified indicator of how water stressed a particular plant is based on the measurement taken from the leaf.

In terms of data logging capabilities of the PSY1, they all remain the same regardless of the application (Leaf or Stem psychrometer chambers). The difference between a leaf and stem psychrometer chamber is the size and plant preparation.

See Full Playlist of PSY1 Psychrometer Youtube Videos Here


Introduction Videos

PSY1 Psychrometer Theory of Operation:

PSY1 Psychrometer Principle of Operation:

Professor Mike Dixon: In Situ Stem Psychrometer, Part A:

Professor Mike Dixon: In Situ Stem Psychrometer, Part B:


Installation Videos

PSY1 Psychrometer Installation:

PSY1 Psychrometer Installation Preparation Video
PSY1 Psychrometer Installation Issues Video
PSY1 Psychrometer De-Installation Video
PSY1 Psychrometer Adjustment Video


Calibration Videos

PSY1 Psychrometer Calibration Procedure:

PSY1 Psychrometer Calibration Sealant Video
PSY1 Psychrometer Calibration Solutions Video
PSY1 Psychrometer Calibration Equipment Video


Cleaning Videos

PSY1 Psychrometer Cleaning With Chloroform:

PSY1 Psychrometer Cleaning With Electronic Contact Cleaner Video


Diagnostics Video

PSY1 Psychrometer Diagnostics:


Leaf PSY - Pepper

Figure 1 – The leaf water potential (MPa) of a pepper plant was monitored by a psychrometer continuously at a 10 minute measurement interval.

Leaf PSY on Pepper

Figure 2 – The diurnal plant water status of a pepper plant was measured by leaf psychrometer, represented by the green line. Measurements were monitored every 10 minutes continuously for a two week period. Irrigation events were represented by the dashed blue lines and occurred on the 4th, 7th, 8th and 14th August 2016 at 19:15, 15:49, 19:40, and 14:30, respectively.

Leaf Psy - Poplar

Figure 3 – Poplar tree instrumented with psychrometers (stem and leaf) and a sap flow meter on the main stem.

Leaf PSY on Poplar

Figure 4 – Diurnal time course showing the plant water status (psychrometers) of both the stem and leaf with concurrent sap flow measurements over a 4-day period. Measurements were collected every 10 minutes with PSY1 and SFM data logging systems. The red line represents the heat pulse velocity (cm/hr), blue line represents the water status on the stem, and the green line represents the water status of the poplar tree.



Units MPa
Range -0.1 MPa to -10 Mpa
(1 to 100 Bars)
Resolution 0.01 MPa (0.1 Bar)
Accuracy ±0.1 MPa (1 Bar)
Response Time Measurement mode: 51 seconds
Live mode: 1 second
Sampling Rate 10 Hz


Computer Interface USB, Wireless RF 2.4 GHz
Data Storage MicroSD Card
Memory Capacity Up to 16GB, 4GB MicroSD card included.

Operating Conditions

Temperature Range -10 to 50°C
R/H Range 0-99%


Logger Length: 170 mm
Width: 80 mm
Depth: 35 mm
Psychrometer Chamber Diameter: 19mm
Depth: 19mm
Depth with calibration chamber: 27mm
Weight with cable: 120g
Leaf Clamp Clamp length with Aluminium Rod: 140mm
Clamp length: 30mm
Clamp width: 21mm
Clamp depth: 25mm
Weight of Clamp: 26g
Weight of Clamp with Aluminium Rod: 50g



Instrument Logging

Analogue Channels 1x Input, (1x Sensor) High precision 24bit ADC circuit
1x Output – PSY Chamber Heater Circuit
Minimum Logging Interval 1 second
Delayed Start Suspend Logging, Customised Intervals
Sampling Frequency 10Hz


Communications USB, Wireless Radio Frequency 2.4 GHz
Data Storage MicroSD Card, SD, SDHC & SDXC Compatible (FAT32 format)
Software Compatibility Windows 8, 8.1, 10 and Mac
Data Compatibility FAT32 compatible for direct exchange of SD card with any Windows PC and Mac
Data File Format Comma Separated Values (CSV) for compatibility with all software programs
Memory Capacity Up to 16GB, 4GB MicroSD card included.

Operating Conditions

Temperature Range -40°C to +80°C
R/H Range 0-100%
Upgradable User Upgradeable firmware using USB boot strap loader function
Internal Battery Specifications
960mAh Lithium Polymer, 4.20 Volts fully charged
External Power Requirements
Bus Power 8-30 Volts DC, non-polarised, current draw is 190mA maximum at 17 volts per logger
USB Power 5 Volts DC
Internal Charge Rate
Bus Power 60mA – 200mA Variable internal charge rate, maximum charge rate of 200mA active when the external voltage rises above 16 Volts DC
USB Power 100mA fixed charge rate
Internal Power Management
Fully Charged Battery 4.20 Volts
Low Power Mode 3.60 Volts – Instrument ceases to take measurements
Discharged Battery 2.90 Volts – Instrument automatically switches off at and below this voltage when no external power connected.
Battery Life varies
  • With a recommended power source connected, operation can be continuous.
  • 3 days at hourly logging interval without chamber heating
  • 1 day with chamber heating
    Small Leaf Clamp for the PSY1 Leaf Psychrometer.