Teledyne 2120XL - Trace Nitrogen Analyzer - Manual (Page 67)

Trace Nitrogen in Argon Analyzer Operation
Teledyne Analytical Instruments 55
regulator on the sample inlet. Do not exceed a maximum of
20 psig (138 kPa).
4.5.2.2 R ECOMMENDED C ALIBRATION G ASES
Teledyne recommends the following gases be used for calibration:
Zero Gas: N
2
-free Ar
Span Gas:
For 0-1 ppm range: 0.7-1.0
ppm N
2
in Ar
For 0-10 ppm range: 7-10 ppm N
2
in Ar
For 0-100 ppm range: 70 – 100 ppm N
2
in Ar (best for overall
accuracy on all ranges)
The first calibration point is fixed by a zero gas. The most
convenient source of nitrogen-free argon is through an activated
molecular sieve scrubber cooled to liquid oxygen temperatures or a
heated transition metal scrubber. A commercially available scrubber the
Teledyne Part number S1748 is ideal for this. Alternatively, a zero gas
cylinder with a low ppb nitrogen level can be used for zeroing in the low
ppm range specified, as long as the N
2
concentration is known.
The second point is fixed by a certified span gas normally supplied
in a high-pressure cylinder.
4.5.2.3 Z ERO C AL
The ZERO button on the front panel is used to enter the zero
calibration function. Zero calibration can be performed in either the
automatic or manual mode. In the automatic mode, an internal
algorithm compares consecutive readings from the sensor to determine
when the output is within the acceptable range for zero. In the manual
mode, the operator determines when the reading is within the acceptable
range for zero. Make sure the zero gas is connected to the instrument.
See Section 3.6
for gas connections.
After pressing the ZERO button, the mode selection screen appears:
Select Zero
Mode : Manual (Auto)
where Manual and Automatic can be toggled back and forth using the