1. How do I know my instrument is reading correctly?
Having confidence in your AQM 65’s readings comes from fully understanding the specifications of your instrument, staying within operational limits (e.g. ambient temperature and humidity range), always following the User Guide with respect to service intervals, and performing regular calibrations according to the needs of your application.
2. What is the difference between a zero and span calibration?
A zero calibration sets the baseline to zero. This involves delivering a controlled flow of zero air to your AQM 60 and adjusting the settings so that the instrument is reading at or near zero. A span calibration ensures the instrument reading is accurate to a known concentration of target gas. It is necessary to perform both a zero and span calibration in sequence to fully calibrate the AQM 60.
3. How do I zero calibrate my AQM 65?
A controlled flow of zero air is delivered to the AQM 65 via the inlet. Zero air can come from a cylinder of certified zero air from a reputable gas supplier, or by filtering ambient air with the appropriate combination of filter media to remove contaminants (e.g. a zero air generator). The AirCal 1000 and AirCal 8000 both include a zero air generator. All gas modules can be zero calibrated using the same source of zero air.
4. How do I span calibrate my AQM 65?
Span calibration ensures your instrument reading is accurate to a known concentration of target gas. A controlled flow of span gas can be achieved by a) obtaining a certified cylinder of calibration gas at the target concentration (the Direct Method), or b) obtaining a certified cylinder of calibration gas at higher concentration then using a gas dilution calibrator (e.g. the AirCal 1000) to dilute to the target concentration (the Dilution Method). After the sensor response to the span gas has stabilized (15 to 30 minutes) the gain and offset parameters are adjusted so the instrument reading corresponds with the span gas concentration. For full instructions on span calibrating your AQM 60 please see the User Guide.
Note: Ozone cannot be obtained in a cylinder due its instability. Instead it must be generated in-situ by photolysis of ambient oxygen using high energy ultra violet light from a high pressure UV lamp. The Aeroqual AirCal 1000 does not contain a UV lamp for Ozone calibrations. For span calibrating the ozone module, we can recommend using the 2B Technologies Model 306 Ozone Calibration Source.
5. What gases do I need to span calibrate my AQM 65?
We recommend using single gas mixtures in a balance of air. Technical Note Calibration gases, regulators and Fittings Open this document for a table that lists the recommended gases to be used to calibrate the most common AQM 65 modules. The table shows concentrations for both the direct method and the dilution method.
Note: Unfortunately, ozone is one of the few gases which cannot be stored in a cylinder due to its high reactivity. Ozone must be generated using a calibrated ozone generator. For calibrating ozone, we recommend the 2B Technologies Model 306 Ozone Calibration Source.
6. Where do I go to get certified calibration gases?
Certified calibration gas can be procured from international providers such as Air Liquide or Linde or Gasco. There is a range of gas cylinder sizes available from small portable and disposable cylinders suitable for air freight through to large cylinders which must be correctly transported using appropriate safety protocols. Smaller cylinder sizes are generally more convenient, especially for field calibrations. Contact your gas supplier for advice, pricing and delivery.
7. What other equipment do I need?
In addition to certified calibration gases you will need to have the correct regulators and tubing for delivery of gas from cylinder to inlet of the AQM 65. All the tubing required is supplied with your AQM 65. Regulators vary according to the type of cylinder used, so we recommend these are purchased from the calibration gas supplier, if you do not have them already. If you are using the Direct Method you will need a fixed flow regulator. If you are using the Dilution Method you will need a pressure regulator; you will also need a gas dilutor such as the AirCal 1000. For ozone generation/calibration you should consider the 2B Technologies Model 306 Ozone Calibration Source.
8. How often should I zero and span calibrate my AQM 65?
We recommend calibration of the AQM 65:
- Upon initial installation
- After relocation
- After any repairs or service that might affect its calibration
- When there is prolonged interruption in operation
- At some routine interval (see below).
The frequency of routine calibration is a trade-off between desired accuracy and economic factors. More frequent calibration gives greater confidence in the accuracy of the measurements, but it also results in higher cost in terms of materials and labour. For simplicity we recommend one of two calibration regimes.
Indicative Monitoring. We recommend an initial field calibration upon deployment followed by at least quarterly gas module calibrations with weekly data inspections to identify early evidence of sensor drift.
Compliance Monitoring. We recommend an initial field calibration upon commissioning followed by at least monthly gas module calibrations and daily data inspections. However, National, State or Federal compliance monitoring regulations may apply to the project and these should be consulted to ensure your intended calibration schedule fully complies.
The AirCal 8000 automatic zero and span module is recommended as a calibration alternative to high labour-intensive site visits. For a full discussion of calibration frequency please see the User Guide.
9. What is the difference between field and factory calibration?
Field calibration is performed by a qualified calibration engineer on site and is the best way to ensure the accuracy of your instrument. Factory calibration is undertaken by Aeroqual prior to shipment of your AQM 65 and the factory calibration certificate is evidence that the instrument meets our quality and performance specifications. If an instrument or module is returned to Aeroqual for a repair or upgrade we will perform a complete factory calibration as part of our standard service.
10. How do I calibrate my Particle Monitor or Particle Profiler?
For a complete discussion of how to calibrate the particle monitor within your AQM 65 please refer to the User Guide or the Dust Sentry Calibration FAQs. A factory service is required once every two years for the particle monitor and once a year for the particle profiler. To have your particle monitor or profiler factory serviced and optics calibrated please contact us for a RMA number.
11. Do I need to calibrate my wind or weather sensors?
All sensors provided to Aeroqual from third party manufacturers come with a factory calibration. It is not necessary to perform a calibration of these sensors upon receipt of the instrument. The method and frequency of calibration can be found in the appropriate Manufacturer’s User Guide supplied with the AQM 65.
12. What do I do if I think the sensor module is not responding correctly during the calibration?
First ensure that you have followed the leak checks and calibration instructions exactly as outlined in the User Guide. Should the expected response not occur, there may be a problem with the gas module. Aeroqual sensor modules have a finite lifetime and an unexpected response may be due to the sensor reaching the end of its life. If you think a gas module has failed or you are unsure please contact your supplier or Aeroqual.