AirCal 8000 (Optional)

The AirCal 8000 is an integrated calibration system for the AQM60. It consists of three main components:

1. Housing: Gas cylinder housing with regulators

2. Gas Dilution Module: 2 span gas inputs with a zero air mass flow meter (MFM) 0-3 SLPM and a mass flow controller (MFC) 0-0.05 SLPM.

3. Zero Air Source: Scrubbing media activated carbon, Purafil chemisorbant and heated carulite

4.5.1. Overview

The AirCal system delivers a controlled concentration of calibration gas for calibration of ambient gas instruments. To do this the calibration gas inside the cylinder is mixed with zero air, which is generated by the scrubbing material inside the AirCal 8000 module. The calibration gas is therefore diluted by the zero air to provide a given concentration which is directed into the AQM60. The concentration of calibration gas is calculated using a dilution ratio which is determined by the zero air and cylinder gas flow rates.

 The zero air generator will deliver a flow rate of approximately 2 – 2.5 LPM. The flow rate of the zero air is monitored using a mass flow meter (MFM).

 The flow rate of the cylinder gas is controlled dynamically using a mass flow controller (MFC). The cylinder gas flow rate can range from between 0.005 – 0.045 LPM. The MFC will adjust the flow of the calibration gas so as to maintain a user defined dilution ratio according the equation:

The user dilution ratio needs to be calculated in order to deliver the required concentration of calibration gas.

Calibration gas

Exhaust USB cable

Nafion Humidifier

(R21) Zero Air

Generator Calibrator

Analyser

Page | 34 Example: If 10ppm of CO was required and the cylinder concentration is 1000ppm, then the required dilution ratio would be 100. The dilution ratio of 100 will be entered into the relevant section in the PC software and the MFC flow rate will automatically adjust to meet the desired calibration gas concentration.

Note: Both the MFM flow rate and the MFC flow rate are logged to the S.D. card so that the user may confirm that the appropriate dilution has been applied.

4.5.2. Pneumatics

4.5.3. Gas cylinder Housing

The AirCal 8000 system allows for two gas bottles to be contained in a secure compartment on the side wall of the AQM enclosure.

To achieve the best performance from the AirCal 8000 it is important to connect gas cylinders with gas concentrations which are appropriate for the calibration being performed. Example cylinder concentrations are as follows: Zero Flow - Sample Flow

Sample

Page | 35 Note 1: The recommended dilution ratio range is between 50 and 500

Note 2: If the cylinder contains calibration gas in a balance of Nitrogen, a minimum dilution ratio of 50 should be used

Gas lines in to AQM

The regulator provides gas into the AQM via 1/8 OD stainless steel tube with a 1/8 compression fitting at the end of the tube to allow connection to the regulator.

Regulators

The AirCal 8000 comes supplied with 2 two stage regulators. The maximum input pressure allowed into the first stage is 3000 psi.

The inlet fitting is a ¼ FNPT. The regulator is also supplied with a

¼ FNPT to 5/8 x 18 thread fitting which will allow it to be attached to many commercially available gas cylinders including the Calgaz range.

The maximum outlet pressure from the second stage is 15 psi. The outlet fitting from the regulator is a 1/8 FNPT thread fitting. The regulator is supplied with a 1/8 FNPT to ¼ Swagelok compression fitting.

Gas Connection

Screw the gas cylinder into the stainless steel regulator and adjust the pressure valve (screw in) until the outlet pressure is 6 PSI.

4.5.4. Configuring the AirCal 8000 scheduler

Calibration can be configured to be carried out automatically at a set time for a chosen running period:

 Define the composition of the cylinders attached to the AirCal inlet ports by clicking “Setup” 

“Calibration configuration” in the software.

 When the calibration dialogue is first accessed there will be no information in the cells describing the port configuration.

 To configure the port click in the cell and enter the appropriate information.

 To configure the run scheduler, right click inside the run scheduler dialogue box and select “add new run”.

 A run may include up to 5 points including zero air which is defined as Port 0.

 A maximum of 3 runs can be configured for automatic calibration.

 The user will need to define the dilution ratio for Port 1 and 2 as well as the run time.

 The schedule can then be selected from the drop down menu to configure the calibration run frequency, day of week/month and start time.

 Once all the parameters have been set click save then click read to ensure the run has been saved.

Page | 36 To remove a run, right click inside the run scheduler and select remove run. Note that run three will be

removed first followed by run two and then run one. Once a run has been removed click save and then click read to make sure that the run has been removed.

Note: The information contained in the Calibration Configuration is stored on the AQM controller and not on the PC containing the Aeroqual software.

4.5.5. The Calibration Record

Each time a scheduled calibration run is executed a calibration log (CL) is written to the s.d card in the date time format: CLMMDDHH, where MM = month, DD = day of month, HH = hour. An example of the

calibration log is shown below.

Monitor ID: 1

Page | 37 The calibration log will record the port specification and the data from all of the configured sensors including the port which is being used and the dilution ratio. In the example shown above Port 1 has been opened and the AirCal is applying a dilution ratio of 10. The flow rate from the MFM and the MFC is recorded to allow the user to confirm that the correct dilution ration has been applied.

4.5.6. Performing a Manual Calibration

Zero Check (Port 0)

 Select “Tools”  “Turn on Zero Scrubber” to initiate the zero air check

 Readings will be taken every minute

 Allow for the sample gas to stabilise (15 minutes). Be aware that there may be some fluctuation in the MFM measurement (±5ml/min)

 To stop the zero check select “Tools”  “Stop Check”

Span Check

 Select “Tools”  “Turn on Span Check” to initiate the span check

 The port and dilution ratio need to be defined

Note: In this example, if port 1 is configured with CO (250 ppm) then the AirCal will deliver 25 ppm CO assuming the correct cylinder has been defined in the calibration configuration dialogue (Section 4.5.4.)

 Readings will be taken every minute

 Allow for the sample gas to stabilise (15 minutes). Be aware that there may be some fluctuation in the MFM measurement (±5ml/min)

 To stop the span check select “Tools”  “Stop Check”

4.5.7. Data Displayed

During normal sampling mode the status bar will read Sample: Ambient and the inlet column will read Sample.

Page | 38 During a scheduled calibration or during a manual calibration, the status bar will indicate what the AirCal is doing. If zero air is being applied the status bar will indicate Sample Port 0 (P0). The flow rate through the MFM will be logged to the S.D. card and be displayed in the real time table. The inlet column will read Zero Air.

When the AirCal is applying a span point the status bar will show Sample Px where x is the port number and DR is the user defined dilution ratio. Both the flow through the MFM and the MFC will logged to the S.D. card and be displayed in real time. The inlet column will display Px.

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