Pyxis ST-725 User manual

ST-725/728 User Manual [email protected] | [phone]

ST-725/728 Ultra-Low Conducvity
Sensors
User Manual
April 4, 2022
Rev. 1.04
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 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 4
4.1 Piping ................................................. 4
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.5 Device Info Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7 Outputs 15
7.1 4–20mA Output Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.2 Adjusng 4–20mA Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.3 Communicaon using Modbus RTU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8 Sensor Maintenance and Precauon 17
8.1 Methods to Cleaning the ST-725/728 Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9 Troubleshoong 17
10 Contact Us 17

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-725/728 User Manual [email protected] | [phone]

1 Introducon
The Pyxis Lab ST-725/728 are industrial grade in-line ultra-low conducvity sensors specially designed for
pure and ultra-pure water applicaons. They can be used for ultra-low conducvity measurement of pure
water, ultra-pure water and deionized water including Boiler Feedwater and Condensate, RO and EDI/EDR
process water, Ion Exchange, Disllaon, Semi-Conductor Cleaning, Degas conducvity and other process
applicaons. These are ’smart sensors’ with a built-in transmier supporng digital and analog signal out-
puts and are designed to simplify eld installaon, calibraon and operaon. The sensors oer simple 3/4”
MNPT threaded installaon and are constructed with a Hastelloy electrode p and stainless-steel body. The
ST-725/728 sensors can be wirelessly calibrated with uPyxis app for mobile or desktop devices when used
with the MA-CR Bluetooth adapter. The sensors both oer two 4–20mA Analog outputs, one for conducv-
ity and one for temperature, as well as RS-485 Modbus output for a broad array of installaons that desire
to connect the smart sensor directly to receiving controller, PLC or DCS network. Both sensors have built-in
RTD for the automac compensaon of sample temperature.
1.1 Features
The ST-725 and ST-728 includes the following features:
• Easy installaon into 3/4” FNPT standard pipe Tee
• The latest short pulse type detecon method technology
• Built-in temperature sensor with automac compensaon
• Front-end fully digital detecon technology
• Accurate and stable measurement with ultra-low dri
• Built-in transmier without preamplier or meter head
• 2x 4–20mA isolated analog and RS-485 Modbus digital outputs
• Stainless-steel housing suitable for harsh environments
• Polluon-resistant and an-interference design
• Specially designed electrode greatly improves the long-term stability of the sensor in complex work-
ing environments and reduces the frequency of cleaning and maintenance
• Ultra-Low Detecon 0.02 µs/cm (50 MΩ Resisvity)
ST-725/728 User Manual [email protected] | [phone]

2 Specicaons
Table 1. ST-725/728 Specicaons
Item*ST-725 ST-728
Part Number (P/N) 53108 53117
Conducvity Range 0.02–200.0 µS/cm 0.02–10.0 µS /cm
Conducvity Precision ±0.1 µS/cm or 1% of the value
4–20mA Range for Temp 32–212 °F (0–100 °C)
Temperature Precision ±1% of the value
Cell Constant (K) 0.3
Sample Pressure Up to 100 psi (0.7 MPa)
Power Supply 22–26 VDC, Power Consumpon 2W
Dimension (L ×W×H) Length 8.46 inch (215 mm), body diameter 1.32 Inch (33.6 mm)
Installaon 3/4” NPT
Body Material 304 stainless steel
Weight 530 g (1.16 lbs)
Operaonal Pressure 100 psi (6.9 Bar)
Operang Temperature 40–104 °F (4–50 °C)
Storage Temperature 20–140 °F (-7–60 °C)
Outputs 8Pin - Isolated 4–20 mA Analog Output & Isolated RS-485 Digital Output
Wet Material HASTELLOY
Rang IP67, Fully Dustproof & Waterproof
Regulaon CE, RoHS Marked
Cable Length 5  (1.5 m) - (Extension Cables Available)
*With Pyxis’s connuous improvement policy, these specicaons are subject to change without noce.
3 Unpacking Instrument
Remove the instrument and nd the standard accessories from the shipping container as listed below. In-
spect 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 service@pyxis-
lab.com.
3.1 Standard Accessories
• One ST-725 (P/N – 53108) or ST-728 (P/N – 53117) sensor
• One MA-1.5CR Cable (1.5 m/4.9  8-Pin Male Adapter/Flying Lead)
• User Manual is also available for download at hps://pyxis-lab.com/support/
ST-725/728 User Manual [email protected] | [phone]

3.2 Oponal Accessories
The following oponal accessories can be purchased via your Regional Sales contact or Pyxis Customer
Service at [email protected]om.
Table 2. Oponal Accessories
Oponal Accessory Part Number (P/N)
MA-CR
(Bluetooth Adapter For uPyxis use with ST-725 / ST-728)
MA-CR
MA-NEB
(Bluetooth-USB Adapter For Desktop use with uPyxis)
MA-NEB
MA-50CR (50’ Extension Cable w/8Pin Adapters) 50743
MA-100CR (100’ Extension Cable w/8Pin Adapters) 50744
Pyxis ST-Series Sensor Cleaning Kit SER-01
POWERPack — 1
(Bluetooth Adapter with Power Supply for 1x Pyxis Sensor)
MA-BLE-1
4 Installaon
The dimensional drawings of the ST-725 are as follows.
Figure 1. Dimension of the ST-725 (mm)
4.1 Piping
Proper Installaon Methods:
• Water owing from the boom up in the pipe keeps the conducvity cell full of water and prevents
air bubbles and air buildup while ensuring accurate measurement. As shown in Figure 2.
• The conducvity cell is located at the boom of the water stream and is less likely to accumulate
air. However, it is worth nong that this type of installaon should avoid the conducvity cell from
reaching in too short and forming a dead zone. As shown in 3.
• The conducvity cell is located on the side of the pipe, which avoids the accumulaon of air to a
greater extent and is less suscepble to contaminant deposits and ensure accurate measurements.
As shown in 4.
ST-725/728 User Manual [email protected] | [phone]

Figure 2. Installaon Method
(1)
Figure 3. Installaon Method
(2)
Figure 4. Installaon Method
(3)
Improper Installaon Methods:
The following 3 installaon methods should be avoided. These installaon methods can easily produce air
bubbles and air accumulaon leading to unstable measurement. As shown in Figure 5.
Figure 5. Installaon methods to be avoided
ST-725/728 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 @ 65mA.
*NOTE*The negave 24V power terminal (power ground) and the negave 4–20mA ter-
minal on the ST-725/728 sensor are internally connected.
Follow the wiring table below to connect the ST-725/728 sensor to a controller:
Table 3.
Wire Color Designaon
Red 24V +
Brown 24V Power ground
White Conducvity, 4–20mA +
Pink Temperature, 4–20mA +
Gray*4–20mA -
Blue RS-485 A
Yellow RS-485 B
Green RS-485 C
Black Shield, earth ground
*Internally connected to the power ground
4.3 Connecng via Bluetooth
A Bluetooth adapter (P/N: MA-CR) can be used to connect the ST-725/728 sensor to a smart phone with the
uPyxis® Mobile App or a computer with the uPyxis® Desktop App. The power should be sourced from a 24
VDC power terminal of a controller. If a controller is not available, the user may also use Pyxis PowerPACK-1
or PowerPACK-4 as an alternave to both an external power supply and a Bluetooth adapter. PowerPACK
from Pyxis Lab oers external power, Input/Output signal, and Bluetooth connecvity.
Figure 6. Bluetooth connection to ST-710SS sensor with MA-CR and uPyxis Mobile App.
ST-725/728 User Manual [email protected] | [phone]

5 Setup and Calibraon with uPyxis® Mobile App
The ST-725 / ST-728 ultra-low conducvity sensors are rigorously calibrated before leaving the factory. As
such, users do not need to calibrate the probe for a period of one year if the sensor is maintained clean.
Users can however calibrate the probe according to their needs and as desired using the MA-CR Bluetooth
adapter and uPyxis APP for mobile or desktop devices.
The ST-725 / ST-728 sensors require a slope calibraon for conducvity. The conducvity can be calibrated
with a standard containing 0.02 µS /cm to 200 µS /cm conducvity (depending on the sensor selected) or
with the sample water itself. The conducvity concentraon of the sample water can be measured using
the Pyxis SP-600 Portable Water Mulmeter (P/N – 50353). Before calibraon, the sensor should be cleaned
with deionized water.
*NOTE*Please take special care to avoid direct contact of the sensor electrode with the
hand or ngers.
5.1 Download uPyxis® Mobile App
Download uPyxis® Mobile App from Apple App Store or Google Play.
Figure 7. uPyxis® Mobile App installaon
ST-725/728 User Manual [email protected] | [phone]

5.2 Connecng to uPyxis® Mobile App
Connect the ST-725/728 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-725/728 and its Serial Number (SN) will be displayed (Figure 8).
4. Press on the ST-725/728 sensor image.
Figure 8.
ST-725/728 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 Slope Calibraon and 4-20mA Span. Follow the screen
instrucons for each calibraon step.
Figure 9.
ST-725/728 User Manual [email protected] | [phone]

5.4 Diagnosis Screen
From the Diagnosis screen, you can check the diagnosis condion. This feature may be used for technical
support when communicang with [email protected].
Figure 10.
ST-725/728 User Manual [email protected] | [phone]

5.5 Device Info Screen
From the Device Info screen you can name the Device or Product and set the Modbus Address
Figure 11.
ST-725/728 User Manual [email protected] | [phone]

6 Setup and Calibraon with uPyxis® Desktop App
The ST-725 / ST-728 ultra-low conducvity sensors are rigorously calibrated before leaving the factory. As
such, users do not need to calibrate the probe for a period of one year if the sensor is maintained clean.
Users can however calibrate the probe according to their needs and as desired using the MA-CR Bluetooth
adapter and uPyxis APP for mobile or desktop devices.
The ST-725 / ST-728 sensors require a slope calibraon for conducvity. The conducvity can be calibrated
with a standard containing 0.02 µS /cm to 200 µS /cm conducvity (depending on the sensor selected) or
with the sample water itself. The conducvity concentraon of the sample water can be measured using
the Pyxis SP-600 Portable Water Mulmeter (P/N – 50353). Before calibraon, the sensor should be cleaned
with deionized water.
*NOTE* Please take special care to avoid direct contact of the sensor electrode with the hand or fingers.
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 13. uPyxis® Desktop App installation
Click Install to start the installation process. Follow the screen instructions to complete the USB driver and
uPyxis® installaon.
ST-725/728 User Manual [email protected] | [phone]
Figure 12. Bluetooth connection to ST-710SS Sensor with MA-CR, MA-NEB and uPyxis Desktop.

6.2 Connecng to uPyxis® Desktop App
Connect the ST-725/728 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 13).
4. If the connecon is successful, the ST-725/728 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 14.
ST-725/728 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 15.
6.4 Calibraon Screen
To calibrate the device, click on Calibraon. On the Calibraon screen there are two calibraon buons,
Slope Calibraon and 4-20mA Span. The screen also displays the reading of the device. The reading refresh
rate is every 4 seconds. Follow the screen instrucons for each calibraon step.
Figure 16.
ST-725/728 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].
Figure 17.
7 Outputs
7.1 4–20mA Output Setup
The 4–20mA output of the ST-725 sensor is scaled as:
• Conducvity:
–4 mA = 0 µS/cm
–20 mA = 200 µS/cm
• Temperature:
–4 mA = 32 °F (0 °C)
–20 mA = 212 °F (100 °C)
The 4–20mA output of the ST-728 sensor is scaled as:
• Conducvity:
–4 mA = 0 µS/cm
–20 mA = 10 µS/cm
• Temperature:
–4 mA = 32 °F (0 °C)
–20 mA = 212 °F (100 °C)
ST-725/728 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 conducvity value corresponding to
the 20 mA output via uPyxis®. For the uPyxis® Mobile App, press 4-20mA Span found on the Calibration
Screen and Reading, shown in Figure 18. For the uPyxis® Desktop App, click 4-20mA Span found on the
Calibration Screen, shown in Figure 19.
Figure 18.
Figure 19.
7.3 Communicaon using Modbus RTU
The ST-725/728 sensor is congured as a Modbus slave device. In addion to the µS/cm conducvity 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-725/728 User Manual [email protected] | [phone]

8 Sensor Maintenance and Precauon
8.1 Methods to Cleaning the ST-725/728 Sensor
The ST-725/728 sensor is designed to provide stable conducvity measurements in pure water, so in general,
the sensor is less likely to become contaminated. If scaling occurs, parcularly iron oxide deposits, they can
be removed using a cleaning soluon capable of removing iron, such as the Pyxis Lab Inline Probe Cleaning
Soluon Kit (P/N: SER-01) which can be purchased at our online E-Store hps://pyxis-lab.com/product/st-
series-probe-cleaning-kit/
Figure 20. Inline Probe Cleaning Solution Kit
To clean the ST-725/728 sensor, soak the lower half of the sensor in 100 ml of in-line sensor cleaning soluon
for 10 minutes or longer (the cleaning soluon should completely submerge the front e lectrode). Aer
soaking, gently scrub the electrode surface with a coon s wab. The cleaned sensor should be thoroughly
cleaned with DI water and recalibrated before use.
9 Troubleshoong
If the ST-725/728 sensor output signal is not stable and uctuates signicantly, make an addional ground
connecon — connect the black (shield, earth ground) wire to a conductor that contacts the sample water
electrically such as a metal pipe adjacent to the ST-725/728 tee.
10 Contact Us
Pyxis Lab, Inc
1729 Majesc Dr. Suite 5
Lafayee, CO 80026 USA
www.pyxis-lab.com
Phone: [phone]
Email: [email protected]
ST-725/728 User Manual [email protected] | [phone]