The SL-series microprocessor based 4-20mA toxic gas monitors were designed to work with Gastronics line of organic electrochemical type sensors. The design criteria was set by one of the worlds leading oil companies.
The criteria included a gas monitor with a hydrogen sulfide sensor that would not go to sleep if the sensor did not see it’s target gas for a period of time. Also, it was required that the sensor would not be temperature or humidity sensitive and as a result would not require compensating circuitry. Additionally, it was desired to have a calibration mode, whereas the monitor could be calibrated without triggering alarms. A Class I, Division 2 approval was required so intrinsically safe barriers would not have to be used. The problem with Class I, Division I approvals for a Division 2 application is that even in a Division 2 area, an intrinsically safe barrier must still be used since that was how the monitor was approved.
