PCX Module

The PCX module is a light scattering based, optical particle counter like the Profiler module, with several important advantages. The PCX module has the capability to report 5 particle mass channels (PM₁, PM_2.5, PM₄, PM₁₀, and TSP) in addition to 6 particle count channels (optional) and includes several ‘smart’ features that improve the performance while reducing operator burden.

·         Integrated Flow Management: Active flow control maintains the flow rate at a steady 1 L/min, ensuring all particles are sized and counted correctly, and minimizing setup and maintenance time by reducing the need for flow checks.

·         Dynamic Heater Control: The PCX module has an integrated inlet heater that can be controlled dynamically if the PCX module is equipped with a temperature and humidity sensor measuring the ambient conditions. This allows for automatic control to the minimum required temperature (and subsequently power consumption) to reduce humidity interference, resulting in increased power savings.

·         Advanced Failure Warning: The PCX module can automatically notify you in the event maintenance may be required. By monitoring and recording the amount of particulate through the module, the instrument can notify you when a filter may require replacement. The system will also monitor pump speed relative to module flow rate and can raise a warning in the event a pump may soon need replacing.

The PCX module contains two LED which can indicate module status. The main LED, which is present on all Aeroqual modules, and a secondary LED which can indicate additional states unique to the PCX module.

The PCX module can provide more detailed error states than previous Aeroqual modules. The table below summarizes which error states the module may present, the possible cause, and the recommend action the user should take.

The zero process in the PCX module has been improved throughout the design lifecycle. V1.2 firmware adds the concept of a ‘zero check’ vs a ‘zero calibration’.

During a zero calibration the system takes current mass at the end of the zero calibration cycle and calculates an offset based on the data reading. During a zero check the system checks to ensure the PM level drops low enough that the baseline is correct but does not apply an offset. The PCX executes an automatic zero check or calibration at start up and every subsequent 1440 minutes (24 hours), by default.

In V1.0 the firmware can only run a zero calibration. By default, this occurs at startup and at the automatic frequency as controlled in the module settings. In V1.2 firmware, the system runs a zero check at startup and daily. The zero calibration can be re-enabled as described in the module settings or executed manually via a button in Connect if required.

Depending on the version of hardware (V1.0 vs V1.2) the sample pump on/off state may also differ during a zero check or zero cycle. Due to changes in flow path to speed up the zeroing process, the sample pump will run during zero checks and zero calibrations for V1.2 hardware.

The zero calibration procedure on the PCX takes 10 minutes by default and causes the baseline to be adjusted. The zero check procedure length varies depending on the ambient levels of dust prior to the zero check, but has a minimum length of 5 minutes, and maximum length of 30 minutes. Generally, this will be around 5-10 minutes except in exceedingly dusty environments.

The module settings of the particle count channels can be used to adjust the function and the timing of zero check and calibration cycles as described below. Modules settings can be accessed via the Diagnostics and Advanced page > Module Settings tab. Modules running V1.0 or V1.1 firmware can only run zero calibrations, while modules with V1.2 firmware can run both a zero check and a zero calibration cycle. The zero check is a pass/fail of the accuracy of the zero, while the zero calibration adjusts the offset.

In V1.0 and V1.1 firmware, the default settings will run a zero calibration 5 minutes after startup and subsequently every 24 hours.

·       TIMA - Auto calibration cycle frequency (in minutes) – how often the zero calibration will run once it has started. Set this value to -1 to disable the auto zero calibration. Default: 1440.

·       TIMR – Zero calibration run time (in seconds) – how long a zero calibration runs for. Default: 600.

·       TEMA – Startup zero calibration delay (in minutes) – once a unit is online and running it will run a zero calibration after this many minutes. Set this value to -1 to disable the startup zero. Default: 5.0.

In V1.2 firmware, the default settings will run a zero check 5 minutes after startup and subsequently every 24 hours.

·       TIMA – ******Auto check cycle frequency (in minutes) – how often the zero check will run once it has started. Minimum value of 10 (or -1) required. Set this value to -1 to disable the auto zero check Default: 1440.

·       TIMR – Zero calibration run time (in seconds) – how long a zero calibration runs for. Default: 600.

·       TEMA – Startup zero check delay (in minutes) – once a unit is turned on and running it will run a zero check after this many minutes. Set this value to -1 to disable the startup zero check. Default: 5.0.

·       PWMH – Auto calibration cycle frequency (in minutes) – how often the zero calibration will run once it has started. Minimum value of 10 (or ≤0) required. Set this value to 1440 to enable daily auto zero calibration. Default: 0.

PCX Firmware V1.2 provides some additional diagnostic detail on the result of the most recent zero cycle (check or calibration) in the diagnostic data channels of the PM measurements. The fifth column has a diagnostic named Zero Status. This value reports the result of the most recent zero, where the values mean:

·       0 – The most recent zero cycle was a calibration that was successful.

·       >0 – The most recent zero cycle was a zero check that was successful, and the value was how long for the check to complete successfully (in seconds).

·       -1 – The most recent zero cycle was a zero check that failed.

·       -2 – The most recent zero cycle was a zero calibration that failed.