I have an Analoxs EIICO that is giving high number readings without being connected to anything. I tried to zero the reading but the adjustment doesn't work. I have also changed the battery but the unit is still giving the same erratic readings. Is this a sensor issue and the sensor needs replacement? If the sensor needs replacement, is Analox the only supplier for the sensor for the Analox EIICO or are there other suppliers for the sensor?