Pyxis ST-774 User manual

ST-774 User Manual [email protected] | [phone]

ST-774 Dissolved Oxygen Sensor
User Manual
February 17, 2021
Rev. 1.00
Pyxis Lab, Inc.
1729 Majesc Dr. Suite 5
Lafayee, CO 80026 USA
www.pyxis-lab.com
© 2017 Pyxis Lab, Inc.
Pyxis Lab Proprietary and Condenal

Table of Contents
1 Introducon 2
1.1 Main Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Specicaons 3
3 Unpacking Instrument 3
3.1 Standard Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 Oponal Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4 Installaon 5
4.1 Piping ................................................. 5
4.2 Wiring ................................................. 6
4.3 Connecng via Bluetooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Setup and Calibraon with uPyxis® Mobile App 7
5.1 Download uPyxis® Mobile App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2 Connecng to uPyxis® Mobile App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3 Calibraon Screen and Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4 Diagnosis Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5 Device Info Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 Setup and Calibraon with uPyxis® Desktop App 12
6.1 Install uPyxis® Desktop App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.2 Connecng to uPyxis® Desktop App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.3 Informaon Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.4 Calibraon Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.5 Diagnosis Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7 Outputs 16
7.1 4–20mA Output Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.2 Adjusng 4–20mA Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.3 Communicaon using Modbus RTU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8 Sensor Maintenance and Precauon 18
8.1 Methods to Cleaning the ST-774 Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.2 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9 Troubleshoong 19
10 Contact Us 19

Warranty Informaon
Condenality
The informaon contained in this manual may be condenal and proprietary and is the property of Pyxis
Lab, Inc. Informaon disclosed herein shall not be used to manufacture, construct, or otherwise reproduce
the goods described. Informaon disclosed herein shall not be disclosed to others or made public in any
manner without the express wrien consent of Pyxis Lab, Inc.
Standard Limited Warranty
Pyxis Lab warrants its products for defects in materials and workmanship. Pyxis Lab will, at its opon, repair
or replace instrument components that prove to be defecve with new or remanufactured components
(i.e., equivalent to new). The warranty set forth is exclusive and no other warranty, whether wrien or oral,
is expressed or implied.
Warranty Term
The Pyxis warranty term is thirteen (13) months ex-works. In no event shall the standard limited warranty
coverage extend beyond thirteen (13) months from original shipment date.
Warranty Service
Damaged or dysfunconal instruments may be returned to Pyxis for repair or replacement. In some in-
stances, replacement instruments may be available for short duraon loan or lease.
Pyxis warrants that any labor services provided shall conform to the reasonable standards of technical com-
petency and performance eecve at the me of delivery. All service intervenons are to be reviewed and
authorized as correct and complete at the compleon of the service by a customer representave, or des-
ignate. Pyxis warrants these services for 30 days aer the authorizaon and will correct any qualifying
deciency in labor provided that the labor service deciency is exactly related to the originang event. No
other remedy, other than the provision of labor services, may be applicable.
Repair components (parts and materials), but not consumables, provided during a repair, or purchased
individually, are warranted for 90 days ex-works for materials and workmanship. In no event will the in-
corporaon of a warranted repair component into an instrument extend the whole instrument’s warranty
beyond its original term.
Warranty Shipping
A Repair Authorizaon (RA) Number 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 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. To receive an RMA you can generate a
request on our website at hps://pyxis-lab.com/request-tech-support/.
Pyxis Technical Support
Contact Pyxis Technical Support at [phone], [email protected], or by lling out a request for
support at hps://pyxis-lab.com/request-tech-support/.
ST-774 User Manual [email protected] | [phone]

1 Introducon
The Pyxis ST-774 sensor is an ultra-low range dissolved oxygen (DO) sensor with a lower limit of detecon
0.4 ppb (µg/L). It is based on the principle of uorescence quenching to determine the paral pressure of
the dissolved oxygen in water. It incorporates Pyxis’ advanced technology in the eld of uorescence. The
ST-774 oers the robustness associated with opcal/luminescent DO sensor technology while achieving the
ultra-low detecon limit compable to an amperometric DO sensor.
The ST-774 and other Pyxis dissolved oxygen sensors (ST-772 and ST-776) measure the oxygen paral pres-
sure that is at equilibrium with the dissolved oxygen in water. The relaonship between the paral pressure
(PO2) and the concentraon of the dissolved oxygen is governed by Henry’s law:
DO/ppb =KPO2.(1)
where Kis Henry’s Law constant, which is a funcon of the temperature and the ionic strength (or conduc-
vity) of the water sample. Pyxis uses the latest USGS equaons to convert the measured paral pressure
and temperature measured by the built-in temperature sensor to a DO value in ppb (or µg/L) for the ST-774
sensor.
The ST-774 sensor oers an easily replaceable, front loading DO membrane cap that has been indepen-
dently developed by Pyxis Lab, with a typical service life of up to two years. The at front-end design of
the ST-774 sensor makes this plaorm less prone to contaminaon or fouling and is very easy to clean. The
sensor body is composed of 304 stainless steel and is well suited for aggressive industrial applicaon use.
The ST-774 sensor oers both 4–20mA and RS-485 Modbus outputs and is Bluetooth enabled when used
in conjuncon with the MA-CR or PowerPACK Series Bluetooth Adapters.
1.1 Main Features
The ST-774 sensor includes the following features:
1. 0.4–2,000 µg/L measurement range
2. Built-in temperature and pressure sensors
3. Accurate and stable measurement with ultra-low dri
4. Built-in transmier without the need of using a preamplier or meter head
5. Dual outputs: isolated 4–20 mA signal and RS-485 Modbus
6. Long-distance transmission with higher stability and accuracy
7. Wireless calibraon, diagnoscs, data trend via uPyxis® App when used with MA-CR Adapter
8. Zero-point calibraon with nitrogen and slope calibraon in O2-containing calibraon gas
ST-774 User Manual [email protected] | [phone]

2 Specicaons
Table 1. ST-774 Specicaons
Specicaon*ST-774
Part Number (P/N) 53715
Dissolved Oxygen Range 0.4–2,000 µg/L (ppb)
Dissolved Oxygen
Resoluon 0.1 µg/L (ppb)
Dissolved Oxygen
Accuracy ±0.3 µg/L (ppb) or ±1%
Method Blue Light Irradiated Excitaon
Red Light Reference
Response Time <60 seconds
DO Membrane Cap Life 2 years
Calibraon High Point Calibraon: 0.1% Oxygen in Nitrogen Gas
Zero Calibraon: 99.999% Nitrogen Gas
Outputs 4–20mA Analog Output,
RS-485 Digital Output with Modbus protocol
Installaon 1/4” OD Swagelok
Cable Length Aached 1.5 m/4.9  8-Pin cable,
MA-1.5CR Cable (1.5 m/4.9  8-Pin Female Adapter/Flying Lead)
Power Supply 22–26 VDC, 0.6 W
Dimension (L ×Dia) 11.8 ×2.36 inch (300 ×60 mm)
Weight †4.74 lb (2150 g)
Material 304 Stainless Steel
Operaonal
Temperature 32–122 °F (0–50 °C)
Pressure Up to 145 psi (1.0 MPa)
Enclosure Rang IP67/IP68
Regulaon CE, RoHS
*With Pyxis’s connuous improvement policy, these specicaons are subject to change without noce.
†Cables excluded
3 Unpacking Instrument
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 accessory items are included. If any item is missing
or damaged, please contact Pyxis Lab Customer Service at [email protected].
3.1 Standard Accessories
The following accessories are included in the ST-774 sensor package:
• DCC-2 Dissolved Oxygen Membrane Cap P/N: 53716
• MA-1.5CR Cable (1.5 m/4.9  8-Pin Female Adapter/Flying Lead) P/N: 50746
• MA-CR Bluetooth Adapter for 8-Pin Sensors P/N: MA-CR
• Bluetooth/USB Adapter for use with uPyxis® Desktop App P/N: MA-NEB
• User Manual available online at hps://pyxis-lab.com/support/
ST-774 User Manual [email protected] | [phone]

3.2 Oponal Accessories
The following oponal accessories can be ordered at or[email protected] or the Pyxis E-Store at hps://pyxis-
lab.com/shop/
Table 2. Oponal Accessories
Accessory Name Part Number (P/N)
MA-CR Bluetooth Adapter For 8-Pin Pyxis Sensors MA-CR
DO-Zero Calibraon Kit 42058
ST-774/776 Flow Cell Assembly — Replacement 53718
DCC-2 Dissolved Oxygen Membrane Cap — Replacement 53716
DCC-3 Pure Nitrogen Gas 99.9999% Cylinder — 58L — Replacement 42059
DCC-4 Oxygen Gas 0.1% in Nitrogen Cylinder — 58L — Replacement 42060
UC-50 Display & Data Logger 43007
ST-774 Premounted Flow & Calibraon Panel 42056
MA-50CR Cable (15 m/50  8-Pin Male/Female Extension Cable) 50743
MA-100CR (30.5 m/100  8-Pin Male/Female Extension Cable) 50744
Pyxis Probe Cleaning Kit SER-01
Figure 1. DO-Zero Calibraon Kit (P/N: 42058)
ST-774 User Manual [email protected] | [phone]

4 Installaon
4.1 Piping
The ST-774 sensor must always be installed in sample ow at or below the upper temperature limit of the
sensor (<122 °F). In many applicaons a sample pre-cooler will be required to adjust sample temperature
to an acceptable level. To properly install the ST-774 sensor, follow the steps below:
1. Mount the ow cell of the sensor to a at surface.
2. Connect the ow cell’s 1/4” Swagelok ports are connected to the sample ow line and allow ow cell
and ports to fully drain.
3. Make sure that the O-ring is installed properly in the ow cell.
4. Hand ghten the ST-774 sensor body to the ow cell.
Figure 2. Pipeline installaon using ST-774 Flow Cell Assembly (P/N: 53718) with dimesions (mm)
ST-774 User Manual [email protected] | [phone]

4.2 Wiring
If the power ground terminal and the negave 4–20mA terminal in the controller are internally connected
(non-isolated 4–20mA input), it is unnecessary to connect the 4–20mA negave wire (gray) to the 4–20mA
negave terminal in the controller. If a separate DC power supply other than that from the controller is
used, make sure that the output from the power supply is rated for 22–26 VDC @ 65 mA.
*NOTE*The negave 24V power terminal (power ground) and the negave 4–20mA ter-
minal on the ST-774 sensor are internally connected.
Follow the wiring table below to connect the ST-774 sensor to a controller:
Table 3.
Wire Color Designaon
Red 24V +
Brown 24V Power ground
Gray*4–20mA -
White 4–20mA +
Pink RS-485 C
Blue RS-485 A
Yellow RS-485 B
Green Earth ground
Black Shield
*Internally connected to the power
ground
4.3 Connecng via Bluetooth
A Bluetooth adapter (P/N: MA-CR) can be used to connect a ST-774 sensor to a smart phone with the uPyxis®
Mobile App or a computer with a Bluetooth/USB Adapter (P/N: MA-NEB) and the uPyxis® Desktop App.
Figure 3. Bluetooth connecon to ST-774 sensor
ST-774 User Manual [email protected] | [phone]

5 Setup and Calibraon with uPyxis® Mobile App
5.1 Download uPyxis® Mobile App
Download uPyxis® Mobile App from Apple App Store or Google Play.
Figure 4. uPyxis® Mobile App installaon
ST-774 User Manual [email protected] | [phone]

5.2 Connecng to uPyxis® Mobile App
Connect the ST-774 sensor to a mobile smart phone according to the following steps:
1. Open uPyxis® Mobile App.
2. On uPyxis® Mobile App, pull down to refresh the list of available Pyxis devices.
3. If the connecon is successful, the ST-774 and its Serial Number (SN) will be displayed (Figure 5).
4. Press on the ST-774 sensor image.
Figure 5.
ST-774 User Manual [email protected] | [phone]

5.3 Calibraon Screen and Reading
When connected, the uPyxis® Mobile App will default to the Calibraon screen. From the Calibraon
screen, you can perform calibraons by pressing on Zero Calibraon,Air Calibraon, and 4–20mA Span.
*NOTE*Before calibrang, remove the ST-774 sensor 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 so cloth, taking special care not to damage the membrane.
Figure 6.
A depressurized nitrogen source can be connected to the sample cell through the 1/4” OD stainless tubing
for the zero-point calibraon. The gas ow rate should be regulated between 2 and 10 liter per minute.
Alternavely, the Pyxis DO-Zero Calibraon Kit (P/N: 42058, seen in Figure 1) can be used for the zero and/or
slope calibraons. The kit contains an aluminum gas cylinder 99.9999% Nitrogen (P/N: 42059) equipped
with ow regulang pressure gauge and an extra sample cell mounted onto a portable stainless steel panel.
See the DO-Zero Calibraon Kit in the ST-774 Datasheet for details.
5.3.1 Zero Calibraon
1. Place the sensor into the sample cell.
2. Turn on a nitrogen gas ow.
3. Allow the gas ow and the temperature to be stabilized for 15 minutes.
4. Once the displayed oxygen and temperature values are stable, press Zero Calibraon to preform a
zero calibraon.
5. If the calibraon is successful, the interface will return a message ”Calibraon Succeeded”. If the
calibraon fails, press Zero Calibraon again and repeat.
ST-774 User Manual [email protected] | [phone]

5.3.2 High Point (Slope) Calibraon
1. Carry out the zero calibraon using nitrogen gas rst. See the Zero Calibraon secon.
2. Place the sensor into the sample cell.
3. Turn on a calibraon gas (with known oxygen concentraon) ow.
4. Allow the gas ow and the temperature to be stabilized for 15 minutes.
5. Once the displayed oxygen and temperature values are stable, press High Point Calibraon
6. Enter the % concentraon of the calibraon gas to preform a high point (slope) calibraon.
7. If the calibraon is successful, the interface will return a message ”Calibraon Succeeded”. If the
calibraon fails, press High Point Calibraon again and repeat.
5.3.3 Air (Slope) Calibraon
1. Place the ST-774 sensor in the air with a stable temperature or in air-saturated water.
2. Let the ST-774 sensor stand for a minimum of 6 minutes. Observe the values being displayed on the
Calibraon screen.
3. Once the displayed oxygen and temperature values are stable, press Air Calibraon to perform an air
(slope) calibraon.
4. Enter the humidity value:
• If you are using air for calibraon, you will need to enter the real-me (current) humidity value.
• If you are using air-saturated water for calibraon, you will need to enter a humidity value of
”1”.
5. If the is successful, the interface will return a message ”Calibraon Succeeded”. If the calibraon fails,
press Air Calibraon again and repeat.
ST-774 User Manual [email protected] | [phone]

5.4 Diagnosis Screen
From the Diagnosis screen, you can check the diagnosis condion as well as Export & Upload. This feature
may be used for technical support when communicang with [email protected].
To preform a Cleanliness and Selife Check, rst select the Diagnosis Condion which denes the uid
type that the ST-774 sensor in currently measuring, then press Cleanliness and Selife Check. If the sensor
is clean, a Clean message will be shown. If the sensor is severely fouled, a Please replace the DO membrane
cap message will be shown. In this case, follow the procedure in the Methods to Cleaning the ST-774Sensor
secon of this manual.
Figure 7.
ST-774 User Manual [email protected] | [phone]

5.5 Device Info Screen
From the Device Info screen. You can name the Device or Product as well as set the Modbus address.
Figure 8.
6 Setup and Calibraon with uPyxis® Desktop App
6.1 Install uPyxis® Desktop App
Download the latest version of uPyxis® Desktop soware package from: hps://pyxis-lab.com/upyxis/ this
setup package will download and install the Microso.Net Framework 4.5 (if not previously installed on the
PC), the USB driver for the USB-Bluetooth adapter (MA-NEB), the USB-RS485 adapter (MA-485), and the
main uPyxis® Desktop applicaon. Double click the uPyxis.Setup.exe le to install.
Figure 9. uPyxis® Desktop App installaon
Click Install to start the installaon process. Follow the screen instrucons to complete the USB driver and
uPyxis® installaon.
ST-774 User Manual [email protected] | [phone]

6.2 Connecng to uPyxis® Desktop App
Connect the ST-774 sensor to a Windows computer using a Bluetooth/USB adapter (P/N: MA-NEB) according
to the following steps:
1. Plug the Bluetooth/USB adapter into a USB port in the computer.
2. Launch uPyxis® Desktop App.
3. On uPyxis® Desktop App, click Device →Connect via USB-Bluetooth (Figure 10).
4. If the connecon is successful, the ST-774 and its Serial Number (SN) will be displayed in the le pane
of the uPyxis® window.
*NOTE*Aer the sensor and Bluetooth is powered up, it may take up to 10 seconds for the
adapter to establish the wireless signal for communicaon.
Figure 10.
ST-774 User Manual [email protected] | [phone]

6.3 Informaon Screen
Once connected to the device, a picture of the device will appear on the top le corner of the window and
the uPyxis® Desktop App will default to the Informaon screen. On the Informaon screen you can set the
informaon descripon for Device Name,Product Name, and Modbus Address, then click Apply Sengs
to save.
Figure 11.
6.4 Calibraon Screen
From the Calibraon screen, you can perform calibraons by pressing on Zero Calibraon,Air Calibraon,
and 4–20mA Span.
*NOTE*Before calibrang, remove the ST-774 sensor 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 so cloth, taking special care not to damage the membrane.
Figure 12.
ST-774 User Manual [email protected] | [phone]

A depressurized nitrogen source can be connected to the sample cell through the 1/4” OD stainless tubing
for the zero-point calibraon. The gas ow rate should be regulated between 2 and 10 liter per minute.
Alternavely, the Pyxis DO-Zero Calibraon Kit (P/N: 42058, seen in Figure 1) can be used for the zero and/or
slope calibraons. The kit contains an aluminum gas cylinder 99.9999% Nitrogen (P/N: 42059) equipped
with ow regulang pressure gauge and an extra sample cell mounted onto a portable stainless steel panel.
See the DO-Zero Calibraon Kit in the ST-774 Datasheet for details.
6.4.1 Zero Calibraon
1. Place the sensor into the sample cell.
2. Turn on a nitrogen gas ow.
3. Allow the gas ow and the temperature to be stabilized for 15 minutes.
4. Once the displayed oxygen and temperature values are stable, click Zero Calibraon to preform a
zero calibraon.
5. If the calibraon is successful, the interface will return a message ”Calibraon Succeeded”. If the
calibraon fails, click Zero Calibraon again and repeat.
6.4.2 High Point (Slope) Calibraon
1. Carry out the zero calibraon using nitrogen gas rst. See the Zero Calibraon secon.
2. Place the sensor into the sample cell.
3. Turn on a calibraon gas (with known oxygen concentraon) ow.
4. Allow the gas ow and the temperature to be stabilized for 15 minutes.
5. Once the displayed oxygen and temperature values are stable, click High Point Calibraon
6. Enter the % concentraon of the calibraon gas to preform a high point (slope) calibraon.
7. If the calibraon is successful, the interface will return a message ”Calibraon Succeeded”. If the
calibraon fails, click High Point Calibraon again and repeat.
6.4.3 Air (Slope) Calibraon
1. Place the ST-774 sensor in the air with a stable temperature or in air-saturated water.
2. Let the ST-774 sensor stand for a minimum of 6 minutes. Observe the values being displayed on the
Calibraon screen.
3. Once the displayed oxygen and temperature values are stable, click Air Calibraon to perform an air
(slope) calibraon.
4. Enter the humidity value:
• If you are using air for calibraon, you will need to enter the real-me (current) humidity value.
• If you are using air-saturated water for calibraon, you will need to enter a humidity value of
”1”.
5. If the is successful, the interface will return a message ”Calibraon Succeeded”. If the calibraon fails,
click Air Calibraon again and repeat.
ST-774 User Manual [email protected] | [phone]

6.5 Diagnosis Screen
Aer the device has been calibrated and installaon has been completed, to check diagnosis, click on Diag-
nosis. When in the Diagnosis screen you can view the Diagnosis Condion of the device. This feature may
be used for technical support when communicang with [email protected]. To preform a Cleanliness
and Selife Check, rst select the Diagnosis Condion which denes the uid type that the ST-774 sensor
is currently measuring, then click Cleanliness and Selife Check. If the sensor is clean, a Clean message
will be shown. If the sensor is fouled, a Please replace the DO membrane cap message will be shown. In
this case, follow the procedure in the Methods to Cleaning the ST-774 secon of this manual.
Figure 13.
7 Outputs
7.1 4–20mA Output Setup
The 4–20mA output of the ST-774 sensor is scaled as:
• Dissolved Oxygen:
–4 mA = 0 ppb
–20 mA = 2000 ppb
ST-774 User Manual [email protected] | [phone]

7.2 Adjusng 4–20mA Span
Users may adjust the output scale using 4–20mA Span to change the dissolved oxygen ppb value corre-
sponding to the 20 mA output via uPyxis®. For the uPyxis® Mobile App, press 4-20mA Span found on the
Calibraon and Reading Screen, shown in Figure 14. For the uPyxis® Desktop App, click 4-20mA Span
found on the Calibraon Screen, shown in Figure 15.
Figure 14.
Figure 15.
7.3 Communicaon using Modbus RTU
The ST-774 sensor is congured as a Modbus slave device. In addion to the dissolved oxygen ppb value,
many operaonal parameters, including warning and error messages, are available via a Modbus RTU con-
necon. Contact Pyxis Lab Customer Service ([email protected]) for more informaon.
ST-774 User Manual [email protected] | [phone]