Apex Instruments XD-502 - 4 Maintenance; Pre-Test Calibrations; Factory Meter Calibration

Apex Instruments performs an initial 5-point calibration following the procedures outlined in EPA
Method 5. The result of the calibration is an average calibration factor Y (V / V , adjusted to the
i w m
same reference temperature and pressure) that is used as the calibration factor for subsequent test
runs. Calibration flow rates are performed at 5 points using the calibration part number below:
DGMC-5A-HF
4.1 Pre-Test Calibrations
4.0 Maintenance
4.1.1 Factory meter calibration
4.1.2 Initial end user calibration checks
Apex Instruments suggests that the end user perform calibration checks on the dry gas meter, thermo-
couples, vacuum gauge and pressure sensors before performing a field test (post-test calibrations fulfill
this suggestion). Perform an audit using a critical orifice set (rated for the intended sampling flow rates)
plugged in to the sample inlet on the console. Run the audit at 1-2 in. Hg (25-50 mm Hg) above the
calculated critical vacuum. Calculate the Y (Gamma) using the standardized orifice’s flow rate and
compare this value to the standardized flow rate metered by the dry gas meter after a minimum of
10 minutes using this formula: (Q / Q ) * 100.
cr(std) m(std)
If these values differ by more than 5%, check the integrity of the console before beginning sampling.
To audit the thermocouples, use a calibrated temperature simulator (NIST-traceable preferred) to
simulate a known temperature and compare the value on the simulator to the console’s displayed
value by plugging in directly to one of the thermocouple jacks on the front of the console. If the
displayed value on the console does not match the simulator, use the console’s menu to offset the
displayed value to match the simulator’s value.
Another quick check is done by taking the TC out of the dry gas meter outlet and dipping it in an ice
bath that also has a calibrated thermometer dipped inside. Ensure the dry gas meter thermocouple
channel reading matches the calibrated thermometer at or near freezing, 32 °F (0 °C). If it is not,
adjust the console reading to match the ice bath’s thermometer.
Apex Instruments, Inc.
45
XD-502 Digital Console