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Zero Point: is the point at which a detector reads zero on a given scale (PPM, % LEL or % Volume Gas). An accurate and stable zero point is important for a gas leak detector where the lower PPM values (20 PPM on a VSR) are critically important in determining an indication of a gas leak. It is likewise important in an explosimeter or catharometer where determination of the potential for an explosive event is critical. Note some units, such as GMI Gaz Meter and Gas Surveyor series, though certified as explosion proof, are required to be turned on outside of an enclosed space. This is because they set their zero point based on the atmosphere sample they initially take into their sensor. If turned on in an area with 2% volume gas, the unit will read 0% volume gas. If the actual % volume gas goes to 5%, the unit will read only 3%. The CATEX+ has a compensation circuit included so that if the unit is turned on and sees 1% volume gas, it will automatically revert to the previous zero point setting from its last use.
AB - CD - EF - GH - IJ - KL - MN - OP - QR - ST - UV - WX - YZ
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