7777, I use a Bridge 2005 five gas analysier which was purchased in 2002 at a cost of 2700.00 USD. In addition to the hand held analysier I am using the PC software which I find highly useful in the diagnostic of engine emission control problems. Some of the features are: ability to calculate and display real timeLamba/air fuel ratio; it's small and light weight; it only takes me five minutes before it's at operating temperature; it performs data capture and with the optional printer (which is great to give an actual read out of each of the customer's trucks on a yearly basis along with the lead in for additional service work); it has an automatic calibration and zero function; the filters aren't that expensive and they are not difficult to change; it has a self contained battery charger which can be plugged into a cigarette lighter; it has a gas accuracy verification test protocol. See your LPG equipment supplier for any other information. I am sure they would be able to assist you.