An IBM compatible laptop computer (Pentium 166 MHz processor) was equipped with a data acquisition system with a 16-channel, 12-bit A/D converter with a capability of up to 1000 Hz per channel (Keithly KPMCI-12 AI, Cleveland, OH). Vacuum sensors with a response time of 1 ms (MICRO SWITCH # 141PC15GL, Freeport, IL) were used to measure the pulsator waveform in the short-pulse tube of the milking machine teat cup. An analogue laser sensor with a response time of 1 ms, a resolution of <20 _m, and a response frequency of 500 Hz (Wenglor # YP 06 MGV-P24, D- 88069 Tettnang, Germany) was clamped to a plastic teat cup to measure liner wall movement (Figures 1 and 2).

Vacuum changes and liner wall movement..

The measuring distance of the laser was 50 mm, with a range of 20 mm. The teat cup liner was marked in the area of the point of laser measurement with a white permanent marking stick (Sanford Corp., Bellwood,IL) to improve reflectance of the liner wall surface to the laser beam. The teat cup liner used for purposes of this report was a DeLaval WC01 in a plastic shell dimensioned to the standard 06 DeLaval shell (Alfa Laval Agri, Kansas City, MO). The teat cup was fitted with a plastic artificial teat dimensioned to ISO Standards (ISO 3918) (1). The point of measurement on the liner wall was as close as possible to the “touch point” of the liner, where the liner walls first touch during the collapse phase. Recordings of liner wall movement and pulse chamber vacuum were taken at 60 pulsations/ min for 10 s duration for analysis. The first and last pulsation cycles were dropped from the analysis and the middle eight pulsation cycles were averaged for final analysis. Pulsation chamber vacuum was also determined with a Surge TRI-SCAN electronic recorder to verify the precision of the Micro Switch transducer and data acquisition system. All comparisons were within ± 2 ms.