Teledyne GFC-7001E - Trace CO Analyzer - Manual (Page 187)

Calibration Procedures Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 187
9.1.2.2. Span Gas
Span Gas is a gas specifically mixed to match the chemical composition of the type of gas being measured at
near full scale of the desired measurement range. It is recommended that the span gas used have a
concentration equal to 80-90% of the full measurement range. If Span Gas is sourced directly from a calibrated,
pressurized tank, the gas mixture should be CO mixed with Zero Air or N
2
at the required ratio.
For oxygen measurements using the optional O
2
sensor, we recommend a reference gas of 21% O
2
in N
2
.
 For quick checks, ambient air can be used at an assumed concentration of 20.8%.
 Generally, O
2
concentration in dry, ambient air varies by less than 1%.
9.1.2.3. Traceability
All equipment used to produce calibration gases should be verified against standards of the National Institute for
Standards and Technology (NIST). To ensure NIST traceability, we recommend to acquire cylinders of working
gas that are certified to be traceable to NIST Standard Reference Materials (SRM). These are available from a
variety of commercial sources.
Table 9-1: NIST-SRMs Available for Traceability of CO Calibration Gases
NIST-SRM TYPE NOMINAL CONCENTRATION
1680b CO in N
2
500 ppm
1681b CO in N
2
1000 ppm
2613a CO in Zero Air 20 ppm
2614a CO in Zero Air 45 ppm
2659a 1 O
2
in N
2
21% by weight
2626a CO
2
in N
2
4% by weight
2745 2 CO
2
in N
2
16% by weight
1 Used to calibrate optional O
2
sensor.
2 Used to calibrate optional CO
2
sensor.
NOTE
It is generally a good idea to use 80% of the reporting range for that channel for the span point
calibration.
For instance if the reporting range of the instrument is set for 50.0 PPM, the proper span gas would be
40.0 PPM
9.1.3. DATA RECORDING DEVICES
A strip chart recorder, data acquisition system or digital data acquisition system should be used to record data
from the serial or analog outputs of the GFC 7001E/EM.
 If analog readings are used, the response of the recording system should be checked against a NIST
traceable voltage source or meter.
 Data recording devices should be capable of bi-polar operation so that negative readings can be recorded.
 For electronic data recording, the GFC 7001E/EM provides an internal data acquisition system (iDAS),
which is described in detail in Section 7.1
APICOM, a remote control program, is also provided as a convenient and powerful tool for data handling,
download, storage, quick check and plotting (see Section 8.4).