Campbell Scientific PVS4151C PVS4100/4120/4150 Portable Automatic Samplers - Page 74
Programming OTHER OPTIONS, 5.6.1 OTHER OPTIONS Overview
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Section 5. Programming 5.6 Programming OTHER OPTIONS 5.6.1 OTHER OPTIONS Overview SET or VIEW This feature allows the user to SET or VIEW the internal Real-Time clock of the microprocessor. This feature allows the user to SET or VIEW the duration for which the sampler will purge the intake line prior to drawing in a sample to the chamber. The maximum allowable setting is 99 seconds. This feature allows the user to change how the pinch valve will operate during sampling cycles. Depending on which generation of sampler the controller is to be used on determines the setting. If this is a new unit, the pinch valve action will have been factory set. Should the controller be used as a retrofit into an older model, the setting may have to be changed. If the sampler has a pinch valve that squeezes shut the discharge tube even during an inactive state, this model is termed as normally closed. Should the tubing be shut only when the pinch valve is energized, it is termed normally open. This is the ONLY setting for the PVSsamplers. This feature will enable or disable the ability of the controller to cease operations when it encounters repeated difficulties in the drawing of samples. The controller normally will attempt to obtain a valid sample by repetition of its programming with extended purge times and vacuum cycles, also extending the time allowed for the acquisition of the sample. When a sample is not obtained, this fact is noted in the controller memory and the program resumes. If after two (2) successive attempts have failed, the controller will Shut Down, halting sampling until operator intervention clears any reason for fault and RESTARTs the program. This is not always a required course of action. If FAULT SHUTDOWN is disabled, the program will record all failures to obtain samples and without further 5-34