The WP4 and WP4-T give water potential readings directly in Megapascals within 5 minutes. It directly measures water potential from 0 to -60 MPa with excellent accuracy. The instrument is easy to use and maintain, and calibration is simple. Using the AOAC-approved Chilled Mirror Dewpoint technique, the WP4 measures a sample's water potential by determining the relative humidity of the air above the sample in a closed chamber. At temperature equilibrium, relative humidity is a direct measurement of water potential, so after measuring a sample, the instrument does some quick calculations to read out directly in water potential units (MPa).
The WP4 currently comes in two models
WP4: Standard model, for basic water potential measurement
WP4-T: WP4 with user-selectable internal temperature control (temperature accuracy is NIST-traceable)
Why Temperature Control?
Though temperature control is usually unnecessary for most water potential measurement applications, there are some instances where it is desirable. For this reason, Decagon offers the WP4-T. There are several advantages in having a temperature-controlled model, here are a few major reasons ....
Research purposes. To study the effects of temperature on the water potential of a sample, comparison of the water potential of different samples independent of temperature, or other water potential studies where temperature control is critical.
To minimize extreme ambient temperature fluctuations. If the laboratory and WP4 temperatures fluctuate by as much as ± 5°C daily, water potential readings can vary as much as ± 0.5 MPa on a dry soil sample.
Specifications
Operating Enviroment: 5 to 43°C (41 to 110° F)
Temperature Control (WP4-T only): 15° to 40° C ±0.2 °C
Sensors: 1. Infrared temperature sensor 2. Cooled-mirror dewpoint sensor
Universal Power: 110V to 220V AC, 50/60Hz
Display: 20 x 2 alphanumeric dot-matrix LCD with backlighting.
Range: 0 to -300 MPa
Accuracy: ±0.1 MPa from 0 to -10MPa ±1% from -10 to -60 MPa
Read time: ~5 minutes
Interface Cable: Standard RS232 serial cable (included)
Data Communications: RS232 compatible, 8 data bit ASCII code, 9600 baud, no parity, 1 stop bit
