AMI Analyzer Manual
Expanded Installation Procedure
17
g) Turn the analyzer Sample/Span/Off valve to the SPAN position.
You will probably see the reading shoot up for a moment as the air in the span gas port is pushed past the
sensor, then the reading will start to stabilize.
h) Allow to stabilize for 2-5 minutes.
This will allow any residual air to be flushed out and the sensor to come to equilibrium.
i)
Verify that the analyzer reads within about 15% of the span gas value.
If it doesn’t, something is wrong. If the sensor reads very low, check it on air, and if that reading is also very
low, replace the sensor (you shouldn’t have to do this with a new sensor!) If the reading is too high, it is
possible that your span gas is contaminated, or you have a leak, or you have made some kind of error. One
thing to note is that if the analyzer temperature is very different from the sensor temperature when you
put it in, the reading will be quite wrong until the sensor has had a chance to equilibrate. Increase the flow
rate by doubling it, and see if the reading decreases after a few seconds. If the reading goes down with
higher flow, you certainly do have a leak. You can also time how long it takes, which will give you an
indication of where the leak is. The longer it takes for the flow change to affect the leak, the further from
the analyzer is the leak source. Fix it by using Snoop and try again.
j)
If so, adjust the analyzer span until it reads the span gas value.
Press the SPAN button. The SPAN flag should appear on the LCD. Press the UP or DOWN arrow buttons
until the reading is correct. After a few seconds the SPAN flag will go out and the analyzer will accept the
new calibration.
k)
Let it go back to normal operation then press the UP arrow and note the number displayed
(the “Calibration factor”).
You can use this to get an idea of the remaining cell life in the future. The analyzer also stores the
calibration values in memory so you can view the history later. When the sensor is new it will have a
Calibration factor (also called Span factor) of about 450. As it gets used up, this number will have to
increase when you span the analyzer until it gets up to around 950 or so (the Calibration factor doesn’t
increase by itself, it only does so when you span the analyzer). You will probably see the span factor remain
fairly constant, then suddenly change. When it does so it means that you will need a new sensor soon. The
sensor behaves rather like a NiCd battery – it is stable until suddenly it starts to fail.
l)
Rotate the valve back to the Sample position.
The analyzer is now set up and calibrated. It is normally good practice to give it a day or two and recheck
the calibration.
