Pyxis CR-301 Corrosion Rate Sensor
User Manual
Revision 1.02 | May 12, 2021
© 2017 Pyxis Lab, Inc. Pyxis Lab Proprietary and Confidential
Warranty Information
Confidentiality
The information contained in this manual is confidential and proprietary to Pyxis Lab, Inc. It shall not be used for manufacturing, construction, or reproduction of the described goods, nor disclosed to others without express written consent.
Standard Limited Warranty
Pyxis Lab warrants its products against defects in materials and workmanship. Pyxis Lab may, at its option, repair or replace defective components with new or remanufactured parts. This warranty is exclusive and supersedes any other written or oral warranties.
Warranty Term
The Pyxis warranty term is thirteen (13) months from the ex-works shipment date.
Warranty Service
Damaged or dysfunctional instruments can be returned to Pyxis for repair or replacement. Short-term loan or lease instruments may be available. Pyxis warrants labor services to meet reasonable technical competency standards. All service interventions require customer authorization. Pyxis warrants these services for 30 days post-authorization, correcting deficiencies related to the originating event. Repair components are warranted for 90 days ex-works. Incorporation of a repair component does not extend the instrument's original warranty term.
Warranty Shipping
A Repair Authorization (RA) Number must be obtained from Pyxis Technical Support before returning any product. Pyxis covers freight charges for shipping replacement or repaired products to the customer. Customers are responsible for return shipping charges. Products returned without an RA number will be returned to the customer.
1 Introduction
The Pyxis CR-301 corrosion sensor measures metal corrosion rate in aqueous environments using the principle of linear polarization resistance (LPR). A small DC polarization voltage is applied to two test metal electrodes, and the resulting current is measured. The polarization resistance (Rp) is calculated from the measured current and applied voltage. The metal corrosion rate, expressed in thousandths of an inch per year (mils per year, MPY), is determined by the formula:
MPY = B/Rp (1)
where Rp is the polarization resistance (LPR) and B is the proportional constant.
The CR-301 sensor calculates Rp by subtracting the solution resistance (Rs), influenced by test solution conductivity, from the total resistance measured between the electrodes. It accurately measures test solution conductivity using the two electrodes and a bipolar pulse technique, similar to other Pyxis conductivity sensors.
Measuring corrosion rates below 0.01 MPY presents a challenge due to the low pico- and nano-ampere current ranges. The CR-301 employs techniques from Pyxis fluorometers, including electromagnetic interference shielding, specialized analog circuit design, and digital signal processing. The proportional constant B has a theoretical value dependent on metal type and size. For a 5 cm² mild steel electrode, B is assumed to be 1.24 MPY·Ω, a common value in LPR research. This constant, also known as the alloy factor, can be adjusted by the user for specific application environments.
Assessing the corrosion status of process equipment is complex, influenced by fluid chemistry, temperature, velocity, and metallurgical composition. The CR-301's measured corrosion rate should not be used in isolation for prediction but can indicate corrosivity trends and correlations with process parameter changes.
Weight loss corrosion coupons are a common industry practice for measuring corrosion rate. LPR offers an instantaneous method, indicating changes within minutes. Theoretically, time-averaged LPR measurements should align with weight loss coupon results. For mild steel corrosion monitoring in cooling water systems, the LPR electrode itself can serve as a weight loss coupon for calibration by adjusting the alloy factor.
Electrochemical noise measurement quantifies localized or pitting corrosion. The CR-301 sensor measures short-circuit electric current flowing between the two LPR measurements. It applies a signal processing algorithm to remove high-frequency noise, calculates the standard deviation of the processed data, and scales it to generate a localized corrosion index. A 304-stainless steel electrode in a 10% ferric chloride solution at 72°F is arbitrarily defined as an index of 100. Real-time electrochemical current noise data can be graphically displayed on an optional Pyxis display panel for visual analysis.
1.1 Features
The CR-301 is a standalone, high-temperature, high-pressure rated LPR corrosion sensor powered by a 24 VDC source (e.g., controller, PLC, DCS). Its Titanium and PEEK construction ensures resilience in extreme environments. It offers an expanded general corrosion range up to 995 mils per year and a localized corrosion index up to 100.
When used with the MA-CR Pyxis Bluetooth Adapter, the CR-301 is configured via the uPyxis APP (Mobile or Desktop). The app allows users to select metallurgy, assign sensor names, view live readings, and apply default or custom alloy factors and measurement ranges. Diagnostic information aids in performance assessment and maintenance needs.
- Anti-electromagnetic interference (anti-EMI) design with Titanium sensor body.
- 2x 4-20mA Outputs (General Corrosion and Localized Corrosion).
- RS-485 Modbus Output.
- Integrated Cooling Fin Design for High Temperature Applications.
- Bluetooth connectivity to uPyxis app when used with MA-CR Adapter.
- Default 4-20mA Output scales and Alloy Factors assigned for selected metallurgy via uPyxis.
- Customization of Alloy Factor and upper MPY / Index (20mA) scale as desired via uPyxis.
- Ultra-low general corrosion rate detection down to 0.001 MPY.
1.2 uPyxis APP Configuration
The uPyxis APP manages Pyxis portable meters and inline sensors on mobile (iOS, Android) and desktop devices. It enables users to configure CR series sensors for specific metallurgy, name sensors, set system and data log frequency, and view live corrosion rate trends. Wireless access to the CR-301 requires the MA-CR Bluetooth Adapter, which is included with each CR-301 purchase.
*NOTE* The uPyxis Mobile APP is evolving rapidly; the latest version is available at no cost on the Apple App Store or Google Play.
2 Specifications
Table 1. CR-301 Specifications
| Item | CR-301 |
|---|---|
| P/N | 51021 |
| General Corrosion Range - MPY (4-20mA Output) | 0.001–995 (Default Assigned MPY is Customizable Via uPyxis) |
| Resolution | 0.001 MPY or 1% of Reading |
| Localized Corrosion Range – Index (4-20mA Output) | 0.001–100 (Default Assigned Index is Customizable Via uPyxis) |
| Conductivity Compensation | 10–50,000 µS/cm |
| Reading Interval | 3 to 1440 Minutes (>3 Minutes Required for Localized Corrosion Data) |
| Alloy Factor Range | 0–3 (Adjustable Default Assigned via uPyxis on Metallurgy UNS Code) |
| Power Supply | 24V DC, 2W |
| Output | Output RS-485 and 4–20 mA Dual Output |
| Weight | 1150g |
| Dimensions (L x D) | 280mm L X 52mm D |
| Installation | 3/4" NPT |
| Enclosure Material | Titanium + PEEK |
| Operating Pressure | Up to 500 psi (34.5 bar) |
| Operating Temperature | -10 – 240°C (14 – 464°F) |
| Storage Temperature | -20 – 70°C (-4 – 158°F) |
| Cable Format | 8Pin - 5 ft. (1.5 m), Extension Cables Available |
| Protection | IP68 |
| Regulation | CE / RoHS |
3 Unpacking the Instrument
Remove the instrument and standard accessories from the shipping container. Inspect each item for damage incurred during shipping and verify all accessory items are included.
3.1 Standard Accessories
3.1.1 CR-301 - Wired / 24VDC LPR Corrosion Sensor Package (P/N 51021)
- One CR-301 sensor, a 5-foot extension cable with connectors, and a 2-foot flying lead cable with one connector.
- One Bluetooth Adapter for CR-301 (P/N: MA-CR).
- One Bluetooth Adapter for PC (P/N: MA-NEB).
- One pair of copper (P/N: 51003) and one pair of mild steel electrodes (P/N: 51002).
- One 2.0 MPY Calibration Check/verification cap (P/N: 51010).
- One 0.1 MPY Calibration Check/verification cap (P/N: 51011).
3.2 Optional Accessories
A table lists optional accessories:
| Accessory Name / Description | Part # | Photo |
|---|---|---|
| MA-10CR-10' Cable for CR300 LPR Sensor | 50741 | [Coiled cable] |
| MA-20CR-20' Cable for CR300 LPR Sensor | 50742 | [Coiled cable] |
| MA-50CR-50' Cable for CR300 LPR Sensor | 50743 | [Coiled cable] |
| MA-100CR 100' Cable for CR300 LPR Sensor | 50744 | [Coiled cable] |
| MA-4.9CR-4.9 Cable For CR300 LPR Sensor | 50745 | [Coiled cable] |
| MA-1.5CR - 1.5 Meter Connection Cable For CR300 w Flying Leads | 50746 | [Cable with flying leads] |
| CR-200 3.6V ER26500 Battery | 50730 | [Cylindrical battery] |
| 2.0 MPY Calibration Cap | 51010 | [Calibration cap] |
| 0.1 MPY Calibration Cap | 51011 | [Calibration cap] |
| CR-Series Bluetooth Adapter - 8Pin | MA-CR | [Bluetooth adapter] |
| CE-01 Mild Steel Electrode Pair | 51002 | [Electrode pair] |
| CE-02 Copper Electrode Pair | 51003 | [Electrode pair] |
*NOTE* Pyxis Lab does not manufacture LPR electrodes. Some electrodes are provided by Pyxis Lab from Metal Samples as a convenience. UNS Codes for each electrode format are provided in the Test Metal Electrodes section. Users may purchase these electrodes directly from Metal Samples at https://www.alspi.com/ms.htm.
4 Installation
The CR-301 sensor is shipped without electrodes installed. Copper and mild steel electrode pairs are included. To install, remove O-rings from the electrode package, place one O-ring onto each sensor threaded rod, and fasten the electrodes, slightly compressing the O-ring. Clean electrodes with isopropanol to remove any oil or foreign materials.
*NOTE* Pyxis recommends wearing latex gloves during electrode installation to prevent contamination with skin oils.
Figure 2. CR-301 Installation in the sample flow line: A diagram illustrates the sensor probe inserted into a pipe via a 3/4-inch threaded tee. The sensor should be fully immersed in the water sample, away from turbulence, and ideally parallel to the flow for optimal performance.
Figure 3. CR-301 Dimensions in Inch (mm): A technical drawing displays the sensor's dimensions, including a 3/4" NPT threaded connection.
4.1 Wiring
Connect the CR-301 sensor to a controller using the following wiring table:
| Wire Color | Designation |
|---|---|
| Red | 24V + |
| Brown | 24V Power ground |
| White | General corrosion rate, 4–20mA + |
| Pink | Localized corrosion rate, 4–20mA + |
| Gray* | 4–20mA - |
| Blue | RS-485 A |
| Yellow | RS-485 B |
| Green | Shield, earth ground |
* Internally connected to the power ground.
The CR-301 features embedded 4-20mA transmitters for general and localized corrosion rates. Default alloy factors and scales are pre-programmed via the uPyxis APP based on selected metallurgy. Users can adjust these values, including the alloy factor, sensor's 4-20 mA range, and controller's 4-20 mA range.
4.2 Connecting via Bluetooth
Wireless connection to the CR-301 requires the MA-CR Bluetooth Adapter and the uPyxis APP. Refer to Section 6.2 for mobile app connection and Section 7.2 for desktop app connection.
5 Instrument Overview
5.1 Test Metal Electrodes
Pyxis provides 5-cm² (0.736 sq inch) metal electrodes for LPR corrosion measurement. Common names, UNS codes, and alloy factors are listed in Table 3.
Figure 10. Test Metal Electrode Dimensions, Inch [mm]: A technical drawing shows the dimensions of a test metal electrode, including its diameter and 4-40 UNC-2B thread.
Table 3. Test Metal Electrode Default Settings
| Common Designation | UNS | Alloy Factor | Default 4–20mA General Corrosion Scale (MPY) | Default 4–20mA Localized Corrosion Scale (Index) |
|---|---|---|---|---|
| Aluminum AA1100 | A91100 | 0.94 | 0–50 | 0–100 |
| Aluminum AA6061 | A96061 | 0.94 | 0–50 | 0–100 |
| Aluminum AA2024 | A92024 | 0.86 | 0–50 | 0–100 |
| Cu/Ni - 70/30 | C71500 | 1.50 | 0–5 | 0–10 |
| Copper 110 ETP | C11000 | 2.00 | 0–5 | 0–10 |
| CDA 687 Aluminum | C68700 | 1.62 | 0–5 | 0–10 |
| Brass Arsenical | ||||
| CDA 642 Aluminum | C64200 | 1.48 | 0–5 | 0–10 |
| Silicon Bronze | ||||
| Arsenical Admiralty Brass CDA443 | C44300 | 1.67 | 0–5 | 0–10 |
| Phosphorized Admiralty Brass CD445 | C44500 | 1.68 | 0–5 | 0–10 |
| Pipe Grade Carbon Steel | A135 | 1.00 | 0–50 | 0–100 |
| Mild Steel C1010 | G10100 | 1.00 | 0–50 | 0–100 |
| Mild Steel C1015 | G10150 | 1.00 | 0–50 | 0–100 |
| Mild Steel C1018-C1020 | G10180 | 1.00 | 0–50 | 0–100 |
| Mild Steel C1080 | G10800 | 1.00 | 0–50 | 0–100 |
| Stainless Steel 304 | S30400 | 0.89 | 0–2.5 | 0–10 |
| Stainless Steel 304L | S30403 | 0.89 | 0–2.5 | 0–10 |
| Stainless Steel 316 | S31600 | 0.90 | 0–2.5 | 0–10 |
| Stainless Steel 316L | S31603 | 0.90 | 0–2.5 | 0–10 |
| Duplex Stainless 2205 - F51 | S31803 | 0.90 | 0–2.5 | 0–10 |
| Duplex Stainless 2507 - F53 | S32750 | 0.90 | 0–2.5 | 0–10 |
| Common Lead | L50045 | 2.57 | 0–2.5 | 0–1 |
*NOTE* Metal electrodes with a different length and diameter may be used if they have a 4-40 internal thread and a surface area of 5 cm². The alloy factor is proportional to surface area; adjustments are needed for different surface areas.
5.2 Default Sensor Settings
The default 4–20 mA outputs for mild steel are scaled as:
- 4 mA = 0 MPY or 0 localized corrosion index.
- 20 mA = 50 MPY (general corrosion).
- 20 mA = 100 Index (localized corrosion).
The sensor defaults to measuring mild steel corrosion. The uPyxis APP assigns default alloy factors and scales. For steel measurement, scale the controller to 20 mA = 50 MPY. Refer to Table 3 for other metallurgies.
5.3 Confirm 4–20mA Output to MPY using the Calibration Check Caps
The CR-301 includes 2.0 MPY and 0.1 MPY calibration check/verification caps. These caps simulate known MPY values when connected to the uPyxis APP and the sensor is configured with default settings. They help confirm the controller reads properly when scaled to match uPyxis defaults.
*NOTE* Allow up to 15 minutes for the corrosion value to stabilize during testing with calibration caps.
To configure the controller's 4–20 mA range:
- Install two new test electrodes (e.g., Steel or Copper).
- Connect the sensor to the appropriate calibration check cap and wait at least 15 minutes for three complete measurements.
- Confirm the controller's analog input 4–20mA scale is programmed correctly so the displayed corrosion rate matches the calibration cap value.
Figure 11. Plug the sensor into the calibration check cap: An illustration shows the sensor being connected to a calibration cap.
6 Setup and Calibration with uPyxis® Mobile App
The CR-301 is pre-configured for mild steel corrosion measurement with the theoretical iron alloy factor. It can be configured for other metals using the uPyxis® Mobile or Desktop App, which also sets 4-20mA scales for general and localized corrosion rates.
6.1 Download uPyxis® Mobile App
Download the uPyxis® Mobile App from the Apple App Store or Google Play.
Figure 12. uPyxis® Mobile App installation: Screenshots show the Pyxis logo, app interface elements, and QR codes for app store downloads.
6.2 Connecting to uPyxis® Mobile App
Connect the CR-301 sensor to a mobile smart phone:
- Open the uPyxis® Mobile App.
- Pull down to refresh the list of available Pyxis devices.
- If connection is successful, the CR-301 and its Serial Number (SN) will be displayed.
- Press on the CR-301 sensor image.
Figure 13. A screenshot of the uPyxis Mobile App showing a connected CR-301 sensor with its SN and status.
6.3 Reading Screen
The uPyxis® Mobile App defaults to the Reading screen upon connection. From here, you can initiate a calibration by pressing 'Slope Calibration' and following on-screen instructions.
Figure 14. A screenshot of the uPyxis Mobile App's Reading screen, displaying corrosion rate, output values, temperature, and a trend graph.
6.4 Setting Screen
The Setting screen allows configuration of Reading Interval, Metal Selection, 20 mA MPY/pitting values, two smoothing factors, and a device password. Ensure you press 'Apply Settings' to save changes.
Figure 15. A screenshot of the uPyxis Mobile App's Setting screen, showing configuration options.
7 Setup and Calibration with uPyxis® Desktop App
The CR-301 sensor can be configured for various metals and 4-20mA scale settings using the uPyxis® Mobile or Desktop App.
7.1 Install uPyxis® Desktop App
Download the latest uPyxis® Desktop software package from: https://pyxis-lab.com/upyxis/. This package includes Microsoft.Net Framework 4.5 (if needed), USB drivers for Bluetooth (MA-NEB) and RS-485 (MA-485) adapters, and the main application. Install by double-clicking 'uPyxis.Setup.exe'.
Figure 16. uPyxis® Desktop App installation: A screenshot shows the uPyxis Setup installer with an 'Install' button.
Click 'Install' and follow the on-screen instructions to complete the USB driver and uPyxis® installation.
7.2 Connecting to uPyxis® Desktop App
Connect the CR-301 sensor to a Windows computer using a Bluetooth/USB adapter (P/N: MA-NEB):
- Plug the Bluetooth/USB adapter into a USB port.
- Launch uPyxis® Desktop App.
- Navigate to Device → Connect via USB-Bluetooth.
- If successful, the CR-301 and its Serial Number (SN) will appear in the left pane.
*NOTE* Allow up to 10 seconds for the adapter to establish a wireless signal after the sensor and Bluetooth are powered on.
Figure 17. A screenshot of the uPyxis Desktop App menu showing connection options, including 'Connect via USB-Bluetooth'.
7.3 Information Screen
Upon connection, the uPyxis® Desktop App defaults to the Information screen. Here, you can set the Modbus Address and click 'Apply Settings' to save.
Figure 18. A screenshot of the uPyxis Desktop App's Information screen, showing device details and the Modbus Address field.
7.4 Reading Screen
The Reading Screen displays current corrosion and pitting data, along with trend data.
Figure 19. A screenshot of the uPyxis Desktop App's Reading screen, showing current data and a trend graph.
7.5 Setting Screen
The Setting screen allows configuration of Reading Interval, Metal Selection, 20 mA MPY/pitting values, and two smoothing factors. Click 'Apply Settings' to save any changes.
Figure 20. A screenshot of the uPyxis Desktop App's Setting screen, showing configuration options.
8 Outputs
8.1 4–20 mA Output Setup
The default scaling for mild steel is: 4 mA = 0 MPY (general) or 0 index (pitting), and 20 mA = 50 MPY (general) or 100 Index (pitting). Users can adjust these scales as needed via the fields shown in Figures 15 and 20. Pre-loaded metallurgies in the Test Metal Electrode Default Settings table offer default 4-20mA scales.
8.2 Communication using Modbus RTU
The CR-301 can be configured as a Modbus slave device. In addition to corrosion rate and index, operational parameters, warnings, and error messages are accessible via Modbus RTU connection.
9 Sensor Maintenance and Precaution
For optimal performance, replace severely corroded sensor metal electrodes. Clean any deposits from the sensor body and electrode base area. Minor corrosion product deposit on the electrode surface is acceptable. Remove non-corrosion product deposits like calcium carbonate scale. Avoid leaving the sensor in stagnant water for extended periods unless that is the intended measurement condition.
10 Regulatory Approval
United States
The CR-301 sensor complies with FCC Rules Part 15 for Class B digital devices, designed to provide reasonable protection against harmful interference in residential installations. This equipment generates, uses, and radiates RF energy. Improper installation or use may cause harmful interference to radio communications. If interference occurs, users are encouraged to try measures such as reorienting antennas, increasing separation between equipment and receivers, or connecting to a different circuit. Consult a dealer or technician for assistance.
Canada
This device complies with Industry Canada license-exempt RSS standard(s). Operation is subject to two conditions: (1) the device must not cause interference, and (2) it must accept any interference, including interference that may cause undesired operation. (Le présent appareil est conforme aux CNR d’Industrie Canada applicables aux appareils radio exempts de licence. L'exploitation est autorisée aux deux conditions suivantes: (1) l'appareil ne doit pas produire de brouillage, et (2) l'utilisateur de l'appareil doit accepter tout brouillage radioélectrique subi, même si le brouillage est susceptible.)
11 Contact Us
For further assistance, please refer to the contact information provided by Pyxis Lab, Inc.
