Model 17i Ammonia Analyzer FAQs

1. Calibration

100% N₂ or zero air is acceptable to perform zero calibrations.

For span calibrations, typically NO balance N₂ is used for NO/NOx/Nt. For NH₃ calibrations, NH₃ balance N₂ is typically used. For NH₃, however, you should not run the calibration gas for long periods of time as it can strip the iron oxide layer from the NH₃ hi temp converter. If NO₂ is to be calibrated, a GPT test should be run same as for NO/NOx analyzer to determine converter efficiency.

You cannot obtain a NO₂ calibration gas bottle at a low enough concertation for this test. Using a multi-gas calibrator to dilute NO₂ gas is also NOT recommended as when diluting the NO₂ with air the NO₂ can react and turn into NO skewing the results low. A GPT test is how to perform calibrations on the NO₂ channel.

For the Model 17i, O₂ is not necessary for calibrations but is for reading sample gas. Calibrations are typically run for only a short amount of time and will not deplete the iron oxide layer in the high temp NH₃ converter. The sample must contain the O₂ level to keep the self-regenerative iron oxide layer intact over longer periods of time. If O₂ is used in the calibration zero or span gas, that is also acceptable.

2. RS485 Communication

For either RS232 or RS485 serial communications, either serial connection port can be used. They are joined in parallel inside the analyzer. You can follow the wiring diagram from the manual. But to make it simple a standard DB9 serial cable may be used. For direct connection to a laptop a NULL (crossover) type cable from computer direct to the analyzer must be used. For connection to some other device such as a hub or something similar a straight type cable must be used.