Under the new AS2290.3:2018 Coal Mining Standard, Section 4.7, gas sensors are required to be calibrated six monthly based upon the following criteria.
1. (a) Where flammable gas sensors used in explosive (or potentially explosive) atmospheres are calibrated in-situ, the calibration shall be conducted at zero, and two points of span check.
NOTE: The highest calibration point is recommended to be 50% LEL.
(b) Infrared sensors with an operating range up to 5%, shall have the calibration conducted at zero and three points of span check.
NOTE: Recommended calibration values of 20%, 40% and 80%.
(c) Infrared sensors with an operating range of greater than 5%, shall have the calibration conducted at zero and five points of span check.
NOTE: Recommended values of 10%, 30%, 50%, 70% and 90%.
(d) All other gas sensors shall have the calibration conducted at zero and three points of span check.
In all cases each instrument must be calibrated at multiple gas levels.
To meet this criteria traditional methods would require multiple gas cylinders at different gas values. This is costly, time consuming, takes up valuable space in laboratories and can create safety issues in regards to manual handling of large gas cylinders.
A solution to these issues is a gas mixer/dilution device.
A single gas mixture connected to a gas mixer and dilution gas creates a simplified process of calibrating instruments at multiple points. By using one gas standard, multiple concentrations can be set to allow calibration at all gas levels.
Zephyr, the latest gas mixer in the CAC GAS range, makes dilution even easier and more accessible. It is the right tool for laboratories looking for an affordable and accurate solution to their calibration needs.
Its 5-inch / 13 cm touch screen enables controlling 2 mass flow controllers to prepare standard gas from a concentrated gas and a diluent gas. These mixtures and dilutions can be programmed into sequences that allow to automatically establish a multipoint calibration curve.
Easy to use and programmable CAC Gas Mixers are a valuable tool for coal mining calibration laboratories.