... -4Q 1.LCD screen display 2.auto-zeroing 3.HC,CO,CO2,O2 Auto gas Analyzer SV-4Q Features Used to measure ... the concentration of HC,CO,CO2,O2,NOx ( ... allowed value for indication error(1 hour).5,indication error: CO:±5% (relative error,0-10%) CO2:±5% (relative ... 220V±10%;50Hz7,preheat time: 5min Other products photos: Auto gas Analyzer SV-4Q