Hobo RX3000 Series User manual

Using the pHionics STs pH Sensor with a
HOBO® RX3000 Station
19315-C
This application note describes how to connect, calibrate, and operate the pHionics STs pH sensor with the HOBO
RX3000 station. The pH sensor is compatible with any RX3000 configuration (cellular, Ethernet, or Wi-Fi) that is
equipped with the optional four-channel analog input module (RXMOD-A1). It is suggested that a 6-watt solar
panel be used to ensure that the battery is kept charged properly.
Portions of the pHionics Technical Manual are used within this application note, but the full manual is available at
http://www.phionics.com/130216_phionics_006.htm#pdf_downloads and should be read and understood before
attempting to use this device with the RX3000 station. Questions regarding the specific application, accuracy or
use of the pHionics sensor should be sent to pHionics directly at http://www.phionics.com/ or
[email protected].
More information on configuring the RX3000 station with HOBOlink® can be found in the HOBOlink User’s Guide at
http://www.onsetcomp.com/support/manuals/17672-hobolink-users-guide.More information on the
RX3000 station hardware can be found in the product manual at http://www.onsetcomp.com/manual/rx3000.
To ensure the best accuracy for your application and to confirm proper operation of the transmitter, periodic
recalibration is recommended. The frequency of the recalibration is best determined empirically for each
application. If you wish to discuss your application to determine the best calibration frequency, contact pHionics
directly at http://www.phionics.com/.

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Wiring to the RX000 Analog Sensor Module (RXMOD-A1)
Calibrating the Sensor using the RX3000 Station and HOBOlink
Important: For the instructions in this section, be sure to follow safe laboratory procedures when handling pH
buffers. Rubber gloves and eye protection are suggested.
1. Immerse the pH sensor in a liquid of a known, stable pH value near the bottom of the range to be
monitored (this example uses a pH 4.01 buffer).
2. In HOBOlink, select Devices from the left menu and then click List and find your station in the list. From
the icon, select Module/Sensor Configuration as shown below.
* Note: Automatic temperature
compensation is provided for the pH
sensor measurement internally in
the sensor. The additional internal
temperature sensor output does not
have to be used to get accurate pH
measurements.

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3. In the Module Configuration screen, configure the RX3000 analog input module for a 1-minute logging
interval. Select “Use excitation power.” Select “Warmup” and enter 3 seconds. Click Next; this will save
the configuration and take you to the next menu item.
4. Select “Enable Graph” and “Enable this channel” in the Sensor Configuration screen. Enter a label if
desired. Select “RAW-C-20, Raw Current -20mA” under Sensor Type/Input. Click Save.
5. Allow the sensor to stabilize (a minimum of 5 minutes).
6. Initiate a call to HOBOlink by pressing the Connect button below the cloud icon on the RX3000 station.
Note: If the station is not currently logging, press the Start button instead of the Connect button to begin
logging data.

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registered trademarks of Onset Computer Corporation. All other trademarks are the property of their
respective companies.
19315-C
7. Take note of the mA value reported on your device page in HOBOlink.
8. Immerse the sensor in liquid of a second known pH value (this example uses a pH 7.00 buffer).
9. After stabilization, initiate another call to HOBOlink by pressing the Connect button below the cloud icon
on the station. Take note of the reported mA value on your device page in HOBOlink as you did in step 7.
10. Select Module/Sensor Configuration again. Select Channel 1 from the left menu to set up scaling for the
sensor. Click “Enable Scaling” and enter the two mA values as your two raw scaled values and the known
concentrations as your respective scaled values. Enter pHionics as the Scaled Measurement Type. Click
Save.
11. From the left menu, select Module 1 and reset the analog module logging interval from 1 minute to your
desired value. Click Save.
12. Initiate another call to HOBOlink or wait until the next scheduled connection for the changes to take
effect.