INSTRUMENT REQUIREMENTS AND METHODS FOR MEASURING VACUUM IN MILKING MACHINES

Abstract

The instrument specifications given in current international (ISO) and national (ASAE) standards state thatmeasured values should be within 90% of the true amplitude of vacuum change at the various locations in the milking machine.Recommendations are given for the minimum sampling rate and response rate of instruments used to measure vacuum changesfor dry, wet, milkingtime, and cleaningtime tests. These minimum performance requirements should ensure that themeasurement accuracy stated in the ISO and ASAE standards are met.A simple method was developed to measure the response rate of a vacuum recording system. The method can be used, quicklyand easily, by field or laboratory technicians to specify the response rate of their vacuum recording systems. The predominanteffects on response rate of vacuum recording systems are caused by the fittings connecting the electronic vacuum recorderto the measurement point. A major source of measurement error was water or milk in connecting tubes and fittings.Dry and wet tests in the milkline and receiver confirmed previous studies showing that the rate of vacuum change during drytests or in dry parts of the milking machine are much lower than those in wet parts of the machine. The fastest vacuum changeswere measured in the short milk tube and mouthpiece chamber during a liner slip in a milkingtime test. Measurements madein the short milk tube during wet tests corresponded well with those made during wet tests at the teatend of the ISO standardudder.