Pyxis ST-772 User manual

ST-772 Dissolved Oxygen Probe
Operation Manual
April. 10, 2020
Rev. A
Pyxis Lab, Inc.
1729 Majestic Dr. Suite 5
Lafayette, CO 80026 USA
www.pyxis-lab.com
© 2017 Pyxis Lab, Inc.
Pyxis Lab Proprietary and Confidential

The information contained in this manual may be confidential and proprietary and is the property of Pyxis Lab, Inc.
Information disclosed herein shall not be used to manufacture, construct, or otherwise reproduce the goods
described. Information disclosed herein shall not be disclosed to others or made public in any manner without the
express written consent of Pyxis Lab, Inc.
Limited Warranty
Pyxis Lab warrants its products for defects in materials and workmanship. Pyxis Lab will, at its option, repair or
replace instrument components that prove to be defective with new or remanufactured components (i.e.,
equivalent to new). The warranty set forth is exclusive and no other warranty, whether written or oral, is expressed
or implied.
Device Warranty Term
The Pyxis warranty term for the ST-772 probe is thirteen (13) months from original shipment from Pyxis. In no event
shall the standard limited warranty coverage extend beyond thirteen (13) months from original shipment date.
Warranty Service
Damaged or dysfunctional instruments may be returned to Pyxis for repair or replacement. In some instances,
replacement instruments may be available for short duration loan or lease.
Pyxis warrants that any labor services provided shall conform to the reasonable standards of technical competency
and performance effective at the time of delivery. All service interventions are to be reviewed and authorized as
correct and complete at the completion of the service by a customer representative or designate. Pyxis warrants
these services for 30 days after the authorization and will correct any qualifying deficiency in labor provided that the
labor service deficiency is exactly related to the originating event. No other remedy, other than the provision of labor
services, may be applicable.
Repair components (parts and materials), but not consumables, provided in the course of a repair, or purchased
individually, are warranted for 90 days ex-works for materials and workmanship. In no event will the incorporation
of a warranted repair component into an instrument extend the whole instrument’s warranty beyond its original
term.
Warranty Shipping
A Repair Authorization Number (RA) must be obtained from Pyxis Technical Support before any product can be
returned to the factory. Pyxis will pay freight charges to ship replacement or repaired products back to the customer.
The customer shall pay freight charges for returning products to Pyxis. Any product returned to the factory without
an RA number will be returned to the customer.
Pyxis Technical Support
Contact Pyxis Technical Support at [email protected] or 1-866-203-8397 (Mo-Fri 7:00AM-5PM MT)

Pyxis ST-772 Operation Manual 3
Table of Contents
1Introducing the Pyxis ST-772 Probe .............................................................................................4
1.1 Features of the Pyxis ST-772 Probe ..............................................................................................4
1.2 Specifications ................................................................................................................................5
1.3 Unpacking the Pyxis ST-772 Probe................................................................................................5
1.4 Standard Accessories ....................................................................................................................6
1.5 Optional Accessories.....................................................................................................................6
2Installation.................................................................................................................................7
3Quick 4-20mA Start.....................................................................................................................8
4Calibration and Diagnosis............................................................................................................9
4.1 Calibration and Diagnosis by uPyxis Mobile App..........................................................................9
4.1.1 Calibration by uPyxis Mobile App .......................................................................................10
4.1.2 4-20mA Span.......................................................................................................................12
4.1.3 Diagnosis .............................................................................................................................12
4.2 Calibration and Diagnosis by uPyxis Desktop App......................................................................14
4.2.1 Calibration...........................................................................................................................16
4.2.2 4-20mA Span.......................................................................................................................19
4.2.3 Diagnosis .............................................................................................................................20
4.3 Calibration Through the Controller.............................................................................................22
5Modbus RTU.............................................................................................................................22
6Probe Cleaning and Maintenance..............................................................................................23
6.1 Cleaning Procedure.....................................................................................................................23
6.2 Other Common Troubleshooting Issues .....................................................................................24

1Introducing the Pyxis ST-772 Probe
The Pyxis ST-772 dissolved oxygen (DO) sensor is based on the principle of fluorescence quenching to
determine the dissolved oxygen content in water. It incorporates Pyxis' advanced technology in the field
of fluorescence detection and uses dual light source detection technology with excitation and reference
light sources, offering a wide detection range and low detection limit. The sensor integrates temperature
and pressure sensors, which can perform temperature and pressure compensation for the measurement
of dissolved oxygen based on ambient environmental conditions present in the application of use. The
ST-772 offers an easily replaceable, front loading DO membrane cap that has been independently
developed by Pyxis Lab, with a typical service life of up to two years. This unique DO membrane cap design
incorporates a black microporous PTFE membrane material designed to provide extreme scratch
resistance, extended life span and simple replacement. The flat front-end design of the ST-772 makes this
platform less prone to contamination or fouling and is very easy to clean. The sensor body is composed
of 304 stainless steel and is well suited for aggressive industrial application use. The ST-772 may be
utilized in a drop in submersed application with the Pyxis submersion rod and stand-pipe assembly, or it
may also be used in an in-line pressurized Tee assembly format. Both options are discussed in the
Installation Section 2.0 of this manual. The ST-772 offers both 4-20mA and RS-485 Modbus outputs and
is Bluetooth enabled when used in conjunction with the MA-CR Bluetooth Adapter.
1.1 Features of the Pyxis ST-772 Probe
The ST-772 includes the following features:
•0.004-20mg/L measurement range
•Built-in temperature and pressure sensor with automatic compensation
•Accurate and stable measurement with ultra-low drift
•Built-in transmitter without preamplifier or meter head
•Dual Outputs both 4-20mA isolated signal or RS-485 Modbus
•Long-distance transmission with higher stability & accuracy
•Wireless Calibration, Diagnostics, Data Trend via uPyxis APP when used with MA-CR Adapter
•The sensor can be Slope calibrated with air or air saturated water
•Zero-point calibration with 5% Sodium Sulfite solution or Nitrogen gas
•Submersible or Inline Pipe Tee installation accessories are optional
•Suitable for dissolved oxygen monitoring of
oActivated Sludge / Aerated Basin
oWastewater & Sewage Processing
oChemical & Process Water Applications
oDomestic Water Applications
oFiltration Applications
oAquaculture
oAgriculture

Pyxis ST-772 Operation Manual 5
1.2 Specifications
Specifications are subject to change without notice. Contact Pyxis ([e-mail]) for an
updated specification list.
Item
Specification
P/N
53703
Measuring Range
0.004-20mg/L
Resolution
0.01mg/L
Accuracy
± 0.1mg / L or ± 1%, whichever is greater
Light Source
Blue Light Irradiated Emission
Red Light Quenching Excitation
Response Time
<60s
Operational Temperature
0 °C –45 °C (32 - 113° F)
Operating Voltage
22 –26V DC, Power 0.6W
Signal Output
4-20mA analog output / RS-485 digital output
Dimension (L x D)
296 x33.6 mm (11.65x 1.32 inches)
Weight
760 g (1.67 lb) cable excluded
Installation Method
Pipeline installation or submerged installation
Material
304 stainless steel
Working Pressure
20 psi
Wet Material
304 stainless steel / PVC and polycarbonate
Cables Provided
MA-1.5CR –8Pin Female Adapter / Flying Lead Cable –1.5m
MA-50CR –8Pin Male/Female Adapter Cable –15m
Calibration
Slope calibration：Air or Air Saturated Water
Zero calibration: 5% Sodium Sulfite or Nitrogen Gas
DO Membrane Cap Life
2 years
Protection Grade
IP-67/IP-68
Regulation
CE
1.3 Unpacking the Pyxis ST-772 Probe
Remove the instrument and accessories from the shipping container and inspect each item for any
damage that may have occurred during shipping. Verify that all items listed on the packing slip are
included. If any items are missing or damaged, please contact Pyxis Customer Service at service@pyxis-
lab.com

Pyxis ST-772 Operation Manual 6
1.4 Standard Accessories
The following accessories are included in the ST-772 probe package (as shown in Figure 1):
•One ST-772 Dissolved Oxygen Probe (P/N - 53703)
•One DCC-1 Membrane Cap for ST-772 (P/N –53712)
•One MA-1.5CR Cable (1.5 Meter/ 4.9 ft 8Pin Female Adapter/Flying Lead)
•One MA-50CR Cable (15 Meter/ 50 ft 8Pin Male/Female Extension Cable)
•One MA-CR Bluetooth Adapter for 8Pin Sensors
•One MA-NEB Bluetooth/USB Adapter for use with Desktop uPyxis APP
•The full instrument manual is available for download at www.pyxis-lab.com/support.html
Figure 1 ST-772 Dissolved Oxygen Probe / DCC-1 Membrane Cap / MA-CR Bluetooth Adapter / MA-NEB USB Adapter
1.5 Optional Accessories
The following optional accessories can be ordered at [e-mail] or the Pyxis E-Store
at www.pyxis-lab.com/shop
Optional Accessory
P/N
MA-CR Bluetooth Adapter for 8-Pin Pyxis Sensors
MA-CR
MA-150-1 Submersion Adapter Mounting Bracket for Floating Install
53705
MA-150-3 Submersion Pipe Assembly with Float Plate
(Floating installation)
50791
MA-120-B Submersion Pipe & Adapter Mounting Bracket
(Fixed installation)
50783
ST-001 Inline Tee Assembly (¾” FNPT – CPVC)
50704
DCC-1 Dissolved Oxygen Membrane Cap - Replacement
53712
MA-50CR (50’ Extension Cable w/8Pin Adapters)
50743
MA-100CR (100’ Extension Cable w/8Pin Adapters)
50744
Pyxis ST-Series Pro
be Cleaning Solution Kit
SER-01

Pyxis ST-772 Operation Manual 7
2Installation
Submersed Floating Installation: The ST-772 may be installed in a submersed/floating application using
the MA-150-1 Submersion Adapter Mounting Bracket and the MA-150-3 Floating Submersion Pipe
Assembly. The ST-772 dissolved oxygen probe needs to be installed as shown in Figure 2. For installation,
users only need to keep the MA-105-1 and MA-105-3 assemblies in place permanently. For probe
replacement and maintenance, users only need to pull the MA-150-3 and DO probe from fixing bracket
vertically (upwards).
Figure 2 ST-772 in a submersed floating installation
Submersed Fixed Installation: The ST-772 may be installed in a submersed/fixed application using the
MA-120-B Submersion Adapter Mounting Bracket. The ST-772 dissolved oxygen probe needs to be
installed as shown in Figure 3. For installation, users only need to keep the MA-120-B assembly in place
permanently. For probe replacement and maintenance, users only need to pull the MA-120-B and DO
probe from fixing bracket vertically (upwards).

Pyxis ST-772 Operation Manual 8
Figure 3 ST-772 in a submersed fixed installation
Pipeline Installation The ST-772 may also be installed in an inline flow application using the Pyxis ST-001
Inline Tee Assembly. The ST-001offers ¾” FNPT Thread or Socket Weld Adapters with Unions for easy
installation and sensor maintenance. Pyxis recommends installation in a vertical flow format from bottom
up to reduce the impact of water bubbles. Install O-ring on the probe and then install the probe into the
tee and ensure the DCC-1 membrane cap is in the direction of water flow as shown in Figure 3.
Figure 4 ST-772 in a pipeline installation using ST-001 inline Tee Assembly
3Quick 4-20mA Start
Follow the wiring table below to connect the ST-772 probe to a controller.
Color
Designation
Red
24V
Brown
0V-

Pyxis ST-772 Operation Manual 9
Color
Designation
Grey
0V
White
4-20mA +
Pink
485GND
Blue
RS-485 A
Yellow
RS-485 B
Green
Shield
*NOTE* The 24V power ground and the 4-20 mA- return are internally connected.
If the 24V power ground and the 4-20 mA return in the controller are internally connected (non-isolated
4-20mA input), it is unnecessary to connect the 4-20 mA- (blue wire) to the 4-20 mA negative terminal in
the controller. If a separate DC power supplier other than that from the controller is used, make sure that
the output from the power supply is rated for 22-26 VDC @ 65mA.
Detailed wiring diagrams for common controllers are available from https://pyxis-lab.com/support-2/
4Calibration and Diagnosis
The ST-772 dissolved oxygen probe is rigorously calibrated before leaving the factory. Users can calibrate
according to their needs. Before calibration, the probe needs to have a relatively stable temperature and
dissolved oxygen reading when placed in the calibration solution or gas.
4.1 Calibration and Diagnosis by uPyxis Mobile App
Connect and power the ST-772 probe using the MA-CR Pyxis Bluetooth adapter (P/N: MA-CR) as shown in
the following connection diagram. The power should be sourced from a 24 VDC power terminal from the
receiving controller. If a controller is not available, please purchase a 24 V power supply that can directly
connect to the ST-772 probe with proper cable connectors from Pyxis.
Figure 5 ST-772 and MA-CR Bluetooth Adapter powered by Receiving Controller

Pyxis ST-772 Operation Manual 10
Download and install the uPyxis APP from Apple iStore or Google Play. Turn on the Bluetooth in the mobile
device being used (please do not pair the device Bluetooth to any Pyxis device, the uPyxis
APP will do the pairing). Open the uPyxis APP in the mobile device. Swipe down to refresh
the phone screen and scan for available Pyxis Bluetooth devices. The discovered devices will
be listed (Figure 4).
Tap the discovered ST-772 probe to connect to the probe. The uPyxis app can identify the probe type if
multiple Pyxis probes are discovered in the scan. For legacy generation Pyxis probes,
a dialog message window will be displayed to ask the user to tell the app
the probe type. In this case, please select ST-772.
As shown in Figure 6, after connected to the ST-772 probe through the MA-
CR Bluetooth Adapter and uPyxis APP, the Calibration Page will display the
current/live dissolved oxygen value. Three functional tabs are available in this page:
Zero Calibration, Slope Calibration, and 4-20mA Span.
4.1.1 Calibration by uPyxis Mobile App
Remove the ST-772 dissolved oxygen probe from the water and wipe it with a damp
cloth to remove debris and any biofouling. If there is water on the membrane, dry
it with a soft cloth, taking special care not to damage the membrane.
Conducting Air Calibration - Place the dissolved oxygen probe in the air with a stable temperature or in
air-saturated water and allow it to stand for a minimum of 6 minutes. Observe the values being displayed
in uPyxis Calibration Page data readout. Once the displayed oxygen and temperature values are stable
proceed by click "Air Calibration" to perform air calibration as shown in Figure 8.
Enter the humidity value into the uPyxis APP through the “Air Calibration Process” outlined using the
following entry values.
•If you are using air for calibration, you will need to enter the real-time (current) humidity value.
•If you are using air-saturated water for calibration, you will need to enter a humidity value of "1".
If the Air-Calibration was successful, the interface will return a message "Calibration Succeeded”. If you
receive a “Calibration Failed” message, please click "Air Calibration" again and repeat.
Conducting ZERO Calibration - Place the probe in Nitrogen Gas or 5% Sodium Sulfite solution (anaerobic
water) and allow the probe to stand for a minimum of 15 minutes. Observe the values being displayed in

Pyxis ST-772 Operation Manual 11
uPyxis Calibration Page data readout. Once the displayed oxygen and temperature values are stable, then
click "Zero Calibration" to perform zero calibration (Figure 7). If the calibration is successful, the interface
will feedback a message "Calibration Succeeded". If the calibration fails, click "Zero Calibration" again.
Figure 6 A ST-772 discoveredby Bluetooth scan
Figure 7 Calibration page
Figure 8 Zero calibration
Figure 9 Air calibration
Figure 10 Calibration feedback

Pyxis ST-772 Operation Manual 12
4.1.2 4-20mA Span
The default 4-20mA span is 20 mA = maximum range (20ppm) and 4 mA = 0 ppm DO in water. Tap
4-20mA Span to change the DO in water value corresponding to the 20 mg/L output (Figure 10).
*NOTE* The 4-20mA Span feature allows users to REDUCE the upper 20mA output scale only.
You cannot INCREASE the upper limit of the sensor.
Figure 11 Enter DO ppm In Water concentration to set 4-20mA
4.1.3 Diagnosis
Tap Diagnosis in the bottom of the app page to launch the diagnosis page (Figures 11 and 12).

Pyxis ST-772 Operation Manual 13
Figure 12 Select Diagnosis Condition
Figure 13 Operation tips
In this page, the raw data measured by the probe is displayed. To help troubleshooting possible issues
with the probe, please remove the dissolved oxygen probe from the water and put the probe in air or air-
saturated water, Nitrogen gas or 5% Sodium Sulfite solution (anaerobic water) respectively to save the
image of these data. This data can be exported to [email protected]om for real-time support in trouble
shooting needs.
In the Diagnosis page, the probe cleanliness check can be performed. Please put the probe in air or air-
saturated water and select the sample condition by tapping Diagnosis Condition (Figure 12). Tap
Cleanliness Check to carry out the check.
As shown in Figure 13, If the DCC-1 (DO membrane cap) is in need of replacement, the APP will display
"Please replace the DO membrane cap". In this case, please replace the DCC-1 dissolved oxygen
membrane cap. If you are in need of a new replacement cap, contact [email protected] for pricing
details.

Pyxis ST-772 Operation Manual 14
Figure 14 Cleanliness check result and raw data
4.2 Calibration and Diagnosis by uPyxis Desktop App
Download and install the uPyxis desktop app from www.pyxis-lab.com/support-2 . Connect and power
the ST-772 probe using the MA-CR Pyxis Bluetooth adapter (P/N: MA-CR) as shown in the following
connection diagram. The power should be sourced from a 24 VDC power terminal from the receiving
controller. If a controller is not available, please purchase a 24 V power supply that can directly connect
to the ST-772 probe with proper cable connectors from Pyxis.
Figure 15 Connect the ST-772 to a computer via Pyxis MA-CR Bluetooth adapter
Establish connection between uPyxis app and the ST-772 through the following steps:
1. Open the desktop uPyxis app.
2. Click Device tap to launch the connection option menu.

Pyxis ST-772 Operation Manual 15
3. Select Connect via MA-NEB Bluetooth USB adapter. (Figure 15)
4. Normally only one Bluetooth adapter is identified by uPyxis. If more than one Bluetooth adapter
listed in the selection dropdown, select the appropriate device to make connection. (Figure 16)
After the connection is established, the ST-772 probe series number and current DO in water
reading are displayed on the left of the information page (Figure 17). In this page, a nickname can
be assigned to the probe. The probe Modbus address can be changed.
USB Bluetooth Adapter (P/N - MA-NEB) for use with PC and uPyxis Desktop App
Figure 16 Connection Options

Pyxis ST-772 Operation Manual 16
Figure 17 Select Appropriate Bluetooth Source
Figure 18 Connected to the ST-772 probe and information page
4.2.1 Calibration
Remove the ST-772 dissolved oxygen probe from the water and wipe it with a damp cloth to remove
debris and any biofouling. If there is water on the membrane, dry it with a soft cloth, taking special care
not to damage the membrane.
Conducting Air Calibration - Place the dissolved oxygen probe in the air with a stable temperature or in
air-saturated water and allow it to stand for a minimum of 6 minutes. Observe the values being displayed

Pyxis ST-772 Operation Manual 17
in uPyxis Calibration Page data readout. Once the displayed oxygen and temperature values are stable
proceed by click "Air Calibration" to perform air calibration as shown in Figure 19.
Enter the humidity value into the uPyxis APP through the “Air Calibration Process” outlined using the
following entry values.
•If you are using air for calibration, you will need to enter the real-time (current) humidity value.
•If you are using air-saturated water for calibration, you will need to enter a humidity value of "1".
If the Air-Calibration was successful, the interface will return a message "Calibration Succeeded” as in
Figure 21. If you receive a “Calibration Failed” message, please click "Air Calibration" again and repeat.
Conducting ZERO Calibration - Place the probe in Nitrogen Gas or 5% Sodium Sulfite solution (anaerobic
water) and allow the probe to stand for a minimum of 15 minutes. Observe the values being displayed in
uPyxis Calibration Page data readout. Once the displayed oxygen and temperature values are stable, then
click "Zero Calibration" to perform zero calibration (Figure 20). If the calibration is successful, the interface
will feedback a message "Calibration Succeeded" as in Figure 21. If the calibration fails, click "Zero
Calibration" again.
Figure 19 Calibration Page

Pyxis ST-772 Operation Manual 18
Figure 20 Air Calibration
Figure 21 Zero Calibration

Pyxis ST-772 Operation Manual 19
Figure 22 Calibration Feedback
4.2.2 4-20mA Span
The default 4-20mA span is 20 mA = maximum range (20ppm) and 4 mA = 0 ppm DO in water. Tap 4-20mA
Span to change the DO in water value corresponding to the 20 mg/L output (Figure 22). *NOTE* The 4-
20mA Span feature allows users to REDUCE the upper 20mA output scale only. You cannot INCREASE the
upper limit of the sensor.

Pyxis ST-772 Operation Manual 20
Figure 23 Set 4-20mA Span
4.2.3 Diagnosis
In this page, the raw data measured by the probe is displayed. To help troubleshooting possible issues
with the probe, please remove the dissolved oxygen probe from the water and put the probe in air or air-
saturated water, Nitrogen gas or 5% Sodium Sulfite solution (anaerobic water) respectively to save the
image of these data. This data can be exported to serv[email protected]om for real-time support in trouble
shooting needs.
In the Diagnosis page, the probe cleanliness check can be performed. Please put the probe in air or air-
saturated water and select the sample condition by tapping Diagnosis Condition (Figure 24). Tap
Cleanliness Check to carry out the check.
As shown in Figure 26, If the DCC-1 (DO membrane cap) is in need of replacement, the APP will display
"Please replace the DO membrane cap" . In this case, please replace the DCC-1 dissolved oxygen
membrane cap. If you are in need of a new replacement cap, contact [email protected] for pricing
details.