Accessories; Calibration Equipment; Sensor Covers - General Monitors 580A Instruction Manual

7.6

Accessories

7.6.1 Calibration Equipment

Calibration accessories may be purchased from GMI. Contact the factory, or your local
representative, for technical or ordering information.
The Portable Calibration Chamber is used to calibrate sensors for any specific
combustible vapor, which has a flash point below ambient temperature. The customer
must provide his own sample of the liquid to use with the chamber. GMI provides a micro-
liter syringe for exact measurement of volumes to be used. Instructions for use are
provided with the chamber.
The Portable Purge Calibrators are available for several common gases, including
hydrogen, methane, ethane, propane and butane. The portable purge calibrator is a
ready-for-use assembly, including a lecture bottle containing approximately 50% LEL of
the gas ordered, plus regulator and an adapter, which fits over the sensor. Replacement
cylinders are also available.

7.6.2 Sensor Covers

The information below is of a general nature. GMI, or your local representative, should be
contacted for specific recommendations:
NOTE: If sensor covers are used, they should remain in place during calibration. If they
are going to be cleaned, the sensor should be recalibrated after the sensor cover
is re-installed. Although several of the available covers do not effect sensitivity or
response-time themselves, accumulations of dust, dirt, water, etc., may do so.
7.6.2.1 Dust Guard Assembly (P/N 10110-1)
The Dust Guard assembly is a simple, threaded stainless steel (type 303) cylinder with a
disposable wire screen at one end. It is easily unscrewed for cleaning and/or replacement
of the screen. The screen material is stainless steel (type 316) with a nominal 40-micron
mesh. This accessory is specially designed to prevent dust and particulate matter from
reaching the sensor flame arrestor. Such debris can plug the screen and limit the amount
of gas reaching the active surface of the sensor. When the Dust Guard is installed, this
problem is minimized and sensor response is virtually unchanged. The Dust Guard is
also available in a kit with twelve replaceable screens. It can be used as an effective
windscreen, and is recommended for corrosive, windy or high temperature environments.
A typical application would be in the area surrounding a drying oven.
7.6.2.2 Sintered Stainless Steel Dust Guard (P/N 1800822)
The construction of this accessory is similar to the Dust Guard assembly, above, but it
has a 1/8" (3mm) thick sintered stainless steel disc at one end. The body material is
stainless steel. It has an internal thread for installation on the sensor body. This Dust
Guard provides protection from fine particulates and windy environments. It should be
used only in dry locations because of the tendency of the sintered disc to absorb water,
which would then act as a gas diffusion barrier until the disc dried-out again. This Dust
Guard reduces sensor response, so it must never be removed for calibration.
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Model 580A