Standard Pump Service UnitIncludesHand vacuum pumpPad of 4.5 x 6.25 in. (11.43 x 15.87 cm) chart forms1 fluid ounce (29.57 cc) bottle of IRROMETER Fluid (concentrated dye) Copy of IRROMETER's Moisture Indicator Reference bookPump FeaturesDesigned for outdoor field use Non-corrosive construction Easily serviceable Long lastingService Units are designed to aid users in the placement and installation, interpretation of readings, and maintenance of IRROMETER soil moisture indicators. Several helpful items are included in the kit. The primary component of a Service Unit is a small hand vacuum pump. The pump is designed to seal on the reservoir portion of the instrument body and is used to create a vacuum manually, evacuating any air contained in the tensiometer. These instruments function with the greatest accuracy when all air has been removed. One Service Unit will service multiple instruments.The standard pump included with the #1001 Service Unit is used for most applications.Operating PrincipleThe Service Units provide the IRROMETER user with valuable tools to ensure their soil moisture indicators function accurately and are easily operated and maintained. The hand vacuum pump serves to evacuate entrapped air from the IRROMETER body which optimizes accuracy and response time. This is important for initial installation and also for periodic maintenance purposes, as air may be drawn into the instrument from the soil under normal operating conditions. Viewing of the fluid level in the instrument and refilling is made easier by using the IRROMETER Fluid concentrate to color the fill water. Included Chart Forms provide a convenient way to graph the periodic IRROMETER readings for use when analyzing soil moisture trends. The instruction booklet provides detailed information on unpacking, preparing, installing, servicing and storing IRROMETERS as well as guidance on instrument placement and data interpretation.