Pyxis ST-601
Operation Manual
17
4.3
Calibration through the Controller
It is recommended that ST-601 calibration is carried out using the uPyxis app as demonstrated in the
sections above. Alternatively, a single point calibration can be carried on the receiving controller by
adjusting the mA-to-ppm CLO2 ratio. A two-point calibration could also be carried out on the controller
by adjusting both the mA-to- ppm CLO2 ratio and the zero-point 4-20mA current value. Please follow
the controller manufacturer’s procedure to carry the 4
-20mA calibration. With the default probe
settings, the controller should be set up to convert 4 mA = 0 ppm and 20 mA = 3000ppm for ST-601
concentrations.
For the single calibration involving the CLO2 sample itself, please determine the CLO2 concentration in
the sample by using the Pyxis SP-910 CLO2 High Range Direct Read method (0-1,500ppm) or by
conventional titration method.
5
Modbus RTU
The ST-601 probes are configured as a Modbus slave device. In addition to the ClO2 value, many
operational parameters, including warning and error messages, are available via a Modbus RTU
connection.
Contact Pyxis Lab Customer Service (
) for more information.
6
Probe Cleaning and Maintenance
The ST-601 probes are designed to provide reliable and continuous ClO2 concentration readings even
when installed in moderately contaminated samples. Although the optics are compensated for the
effects of moderate fouling, heavy fouling will prevent the light from reaching the sensor, resulting in
false readings.
The ST-601 probes are designed to be easily removed, inspected, and cleaned if required. It is suggested
that the ST-601 probes be checked for fouling and cleaned/calibrated on a monthly basis. Heavily
contaminated samples may require more frequent cleanings however most ClO2 storage tanks are quite
clean internally and periodic sensor cleanliness checks with uPyxis will help validate the actual
application need for cleaning and calibration.
6.1
Cleaning Procedure
A light deposit inside the probe quartz tube can be cleaned by a Q-tip. Aged heavy deposition, especially
carbonate and iron oxide deposits, can be removed using a cleaning solution that is capable of removing
these inorganics, such as the Pyxis ST Series Sensor Cleaning Solution Kit (P/N SER-01) available from
Pyxis online EStore /Catalog
https://pyxis-lab.com/product/st-series-probe-cleaning-kit/
. The
Soak the lower half of the ST-601 probe in 100 mL probe cleaning solution for 10 minutes. Rinse the ST-
601 probe with distilled water and then check for the flashing blue light inside the ST-601 probe quartz
tube. If the surface is not entirely clean, continue to soak the ST-601 probe for an additional 10 minutes.
Repeat as needed.