Hach 900 MAX manual Section, Intake Tube Pre-Rinse, Sample Retry

Section 1

Intake Tube Pre-Rinse

The liquid sensor also rinses the intake tubing with the liquid from the sample source before taking each sample.

Upon sample initiation, the pump purges the intake line. The pump then reverses, pulling liquid through the tubing, until it reaches the liquid sensor. When the sensor detects liquid, the pump purges back to the source, and then draws a sample. After the desired sample is collected, the pump purges the intake line and awaits the next sample cycle. The sampler can be programmed for up to 3 rinses before each sample.

Sample Retry

The liquid sensing system permits the sampler to repeat a collection cycle if a sample is not obtained during the regular cycle.

The intake line length is user-programmed into the sampler memory. For a line length of 3 to 99 feet, the sampler has a built-in “look up” table that detects the maximum time required for liquid to reach the sensor. If liquid does not reach the sensor within the defined time period, the pump will automatically purge the intake line and initiate another sample cycle. The sampler may be programmed for up to three repeated attempts. If a sample is not obtained, the sampler retains in memory the time, date and reason for the missed sample.

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Principle of Operation	8990int.fm