Gemini 501-B, Руководство пользователя

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15
6.0 Servicing
6.1 General
The servicing section discusses the procedure for internal calibration check, routine maintenance
information, problem diagnostics, causes, and remedies.
6.2 Calibration and Working Standards
Though the instrument has been calibrated at the factory before shipment, there is no assurance that the
calibration will remain unchanged after it has been used in the field for any length of time. By using a working
standard, you can check your own calibration and avoid returning the instrument to the factory.
A working standard, in the form of two commercial smoke detectors (one ion chamber type and the other
photoelectric), can be used to determine the reference benchmarks while the instrument is new and in
calibration. The benchmarks are the alarm threshold of the two detectors based on the LCD sensitivity
readings of the instrument. Store these two working standard detectors and only use them to check the
Gemini Tester.
Any change in the alarm thresholds of these two detectors in subsequent tests can reasonably be assumed
to be a shift in calibration of the instrument, rather than to shift in detector sensitivity. Periodic checking with
the standards may be used as the criteria for need of service action (i.e., cleaning of small orifices and filter
change) and thus to insure correct calibration.
The two working standard detectors we recommend are the System Sensor 1451 ionization type and the
ESL 611U pulse LED photoelectric. Other well-designed detectors may also be used.
After familiarizing yourself with the instrument by triggering the alarm on several smoke detectors and
recording the concentration/sensitivity readings, the alarm threshold for the two standard detectors should
then be established. We suggest that the average of several replicate runs be taken. All readings for a single
detector should be within 5 mm (one tic mark space = 5 mm) while the difference between the two detectors
may be large.
Calibration check using the working standards may be performed after the instrument has tested over a few
hundred detectors. The frequency for check should be guided by your own test experience.
Three main causes for shift in calibration are: (1) Clogging of the small orifices (holes) in the nebulizer or
impactor. (2) Vacuum filter overload. (3) Not using Rudol Liquid. (See Table 1: Problem Diagnostics, on
page 15 to remedy these situations.)