Calibration Gas Humidifier

Gas Calibration

All photoionization (PID) analyzers, when calibrated with dry calibration gas, can be affected by changes in ambient humidity conditions (see graph below). A decrease in response with increasing humidity results from absorption of the light energy by the water (in the 125-105 nm region). The experienced user compensates for these effects by calibrating the unit with standards prepared at ambient humidity levels. While not particularly difficult this can become a cumbersome and time consuming procedure.

Here’s a simple way to calibrate your Model 101 analyzer to ambient humidity conditions.

Gas Calibration Curve (Graph)

Process Analyzers now offers a unique, inexpensive and easy-to-use device for calibrating our photoionization based analyzers {PI, IS, 102} at ambient humidity conditions. This simple is called a calibration gas humidifier. Consisting mainly of a permeable membrane, it is placed in-line between the calibration gas source and the probe of the PID analyzer. Once in place, the standard Model 101 calibration procedure is follow (see below). The membrane “instantaneously” equilibrates the calibration gas to ambient humidity conditions. As a result, ambient humidity effects are eliminated. The calibration gas humidifier lets you read directly in ppm with virtually no inaccuracies-even in high humidity conditions.



for the Process Analyzers Model 101

To perform ambient humidity calibration

  1. Turn on the 101 and check the Zero in the Standby Mode.
  2. Turn the Range switch to 0-2000
  3. Connect the tygon tubing end of the humidifier to the span gas cylinder regulator.
  4. Connect the fitting and (white polypropylene) of the humidifier to the 101 probe extension.
  5. Open the valve on the span gas cylinder.
  6. When the reading stabilizes (15-30 seconds), adjust the Span Pot until the meter reads the correct value for the calibration gas in use. For a benzene-referred calibration using Process Analyzers span gas, adjust the meter to read the value on the cylinder label (normally about 55 oom).
  7. The 101 is now calibrated for direct reading on the calibration gas (e.g. benzene) at ambient humidity.
  8. The calibration can be adjusted for changes in humidity by repeating the process.
  9. The Gas Humidifier can be retained to analyze samples which have higher or lower humidity than ambient. Care should be taken to determine whether the compounds of interest are compatible with the humidifier. 

NOTE: These procedures must be followed using our membrane device to provide correlative data between PID and FID analyzers for soil sampling equivalency  determinations (such as Florida DER 17.70 regulations).

Order Info

Catalogue NumberDescription
20-ME11012TT3-1Calibration Gas Humidifier Ideal for use with the Process Analyzers Calibration Kit. (Kits include two span gas cylinders, one regulator, a complete 'O' ring kit, a set of replacement fuses and a set of screwdrivers.
81-101-352PI Calibration Kit
81-IS101-352IS Calibration Kit

Our Company

PID Analyzers is an international leader in environmental monitoring technologies. Process Analyzers offers a complete range of photoionization-based instruments for industrial, hygiene, pollution measurement and process analysis. We also manufacture x-ray fluorescence analyzers, micro-analysis systems and sensitive balances for scientific gas blending and other ultra-precise weighing.

For further information on Process Analyzers products and accessories call (508) 660-5001 and ask for the sales department.

To order, call us toll-free at (800) 724-5600.

Specifications subject to change without notice PFS1191

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