Decagon Devices 5TE Operator's Manual

Also see for 5TE: Operator's manual

Decagon Devices 5TE Operator's Manual Manual pdf 11 page image

5TE Operator’s Manual3.Theory7polar molecules that are in solution. EC is measured byapplying an alternating electrical current to two electrodes,and measuring the resistance between them. Conductivity isthen derived by multiplying the inverse of the resistance(conductance) by the cell constant (the ratio of the distancebetween the electrodes to their area).The 5TE uses a 2-sensor array to measure the EC. The arrayis located on the screws of two of the 5TE prongs. Smallamounts of oil from skin contact with the screws willcause significant inaccuracy in the EC measurement.See the sensor cleaning section at the end of this manual forinstructions on cleaning the sensors if contamination occurs.The 5TE uses a two electrode array to measure the bulk ECof the surrounding medium. The bulk EC measurement iscalibrated at the factory to be accurate within ±10% from 0to 7 dS/m. This range is adequate for most field, greenhouseand nursery applications. However, some special applica-tions in salt affected soils may requires measurements withbulk EC greater than the specified range. The 5TE will mea-sure up to 23.1 dS/m bulk EC, but user calibration isrequired above 7 dS/m. Additionally, EC measurementsabove 7 dS/m are very sensitive to contamination of theelectrodes by skin oils, etc. Be sure to read sensor cleaningsection at the end of the manual if you plan to measure theEC of salty soils.Converting Bulk EC to Pore ECFor many applications, it is advantageous to know the elec-trical conductivity of the solution contained in the soil pores(σp), which is a good indicator of the solute concentration in