Daviteq pH transmitter
PH
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1. Introduction
Overview
PH is a transmitter with built-in ultra-low-power amplifier for connecting to external pH probe and temperature sensor like PT100 or PT1000, based on 14-year experience in design and manufacturing Industrial sensor of Daviteq Company. The transmitter can be configured with fixed temperature compensation or automatic temperature compensation. It has been factory pre-calibrated for high accuracy and quick set-up. The PH transmitter can be integrated into the wireless node from Daviteq, such as Sub-GHz WS433, LoRaWAN WSLRW, and Sigfox WSSFC, to build the complete wireless PH transmitter.
Some typical applications are pH and temperature monitoring for factories, agriculture, boilers...
Specification
pH Sensor Input: pH sensor
pH Measuring range: pH 0∼14
Resolution of pH: 0.1
Accuracy of pH: ±0.1
Temperature Sensor Input: PT100, PT1000
Temperature measuring range: 0∼100℃
Temperature resolution: 0.1℃
Working temperature: -40∼60℃
pH Connector: BNC
Temperature Connector: Terminal block
2. Principle of Operation
A pH transmitter is responsible for converting the signal from a pH sensor into a readable and transmittable format. Here's how it operates:
1. Signal Reception:
Input Signal: The transmitter receives the voltage signal generated by the pH sensor, which corresponds to the pH level of the solution. The pH level also is adjusted based on the environment temperature value from temperature sensor (auto compensation) OR based on fixed temperature value (manual compensation).
2. Signal Amplification:
Amplification: The transmitter amplifies the weak voltage signal from the sensor to make it suitable for further processing.
3. Analog to Digital Conversion:
Conversion: The amplified signal is converted from an analog signal to a digital signal for accurate processing and transmission.
4. Calibration:
Calibration: The digital signal is calibrated to correspond to the pH scale (0-14), ensuring accurate pH readings.
5. Signal Transmission:
Output Signal: The calibrated pH value is transmitted as an output signal, which can be in various forms such as 4-20 mA, digital communication protocols, or wireless signals.
Display and Monitoring: The output signal can be displayed on a monitor or integrated into a control system for real-time monitoring and control.
3. Calibration
Calibrating a pH transmitter ensures accurate and reliable pH measurements. Here’s a step-by-step guide:
1. Preparation:
Clean Equipment: Ensure the pH sensor and reference electrode are clean.
Buffer Solutions: Prepare standard buffer solutions (e.g., pH 4.0, pH 7.0, and pH 10.0).
2. Initial Setup:
Power On: Turn on the pH transmitter and allow it to stabilize.
Temperature Compensation: If the transmitter has automatic temperature compensation, ensure it is enabled.
For LoRaWAN/Sigfox/Sub-Ghz pH transmitter, write 1 to AUTO_TEMPERATURE_COMPESATION_ENABLE for auto-compensation and write 0 to AUTO_TEMPERATURE_COMPESATION_ENABLE for manual-compensation with value of TEMPERATURE_FOR_MANUAL_COMPENSATION as reference value for compensation using online downlink or offline tool
3. Calibration Process:
Zero Calibration:
Immerse the pH sensor in the pH 7.0 buffer solution.
Allow the reading to stabilize.
Adjust the transmitter to read exactly pH 7.0.
For LoRaWAN/Sigfox/Sub-Ghz pH transmitter, firstly write 1 to CALIB_ENABLE to enable calibration during max 1 hour. Secondly, write 7 to CALIB_STD_PH_RESOLUTION via downlink.
Note:
For LoRaWAN/Sub Ghz device, there must be an any uplink to initiate sending downlink to device.
For Sigfox device, there must be an PARAMETER_UPDATES uplink to initiate sending downlink to device.
Slope Calibration:
Rinse the sensor with distilled water and immerse it in the pH 4.0 or pH 10.0 buffer solution.
Allow the reading to stabilize.
Adjust the transmitter to read the correct pH value of the buffer solution.
For LoRaWAN/Sigfox/Sub-Ghz pH transmitter, firstly write 4 or 10 to CALIB_STD_PH_RESOLUTION via downlink.
For LoRaWAN/Sigfox, after this downlink or 1-hour, the device send the CALIB_CHECK uplink to inform the result of the calibration process (fail/success).
4. Verification:
Check Accuracy: After calibration, verify the accuracy by measuring a different buffer solution.
Repeat if Necessary: If the readings are not accurate, repeat the calibration process.
5. Documentation:
Record Settings: Document the calibration settings and any adjustments made.
Maintenance Schedule: Establish a regular calibration schedule to maintain accuracy.
4. Application Notes
5. Installation Notes
Installation Notes for pH Transmitter
1. Preparation:
Power Supply: Ensure the power supply matches the voltage and current requirements of the transmitter.
Tools: Gather necessary tools such as a multimeter, screwdriver, wire strippers, and connectors.
2. Mounting:
Location: Choose a clean, dry, and accessible location for the transmitter.
Secure Mounting: Mount the transmitter securely using screws or brackets.
3. Electrical Connections:
Wiring: Connect the transmitter to the pH sensor using appropriate gauge wires. Secure connections with wire nuts or terminal blocks.
Power Supply: Connect the power supply to the transmitter, ensuring it is turned off during installation.
4. Configuration:
Calibration: Calibrate the transmitter using standard buffer solutions (e.g., pH 4.0, pH 7.0, and pH 10.0).
Programming: If using a programmable transmitter, configure it to match the required settings.
5. Testing:
Initial Test: Turn on the power supply and test the transmitter to ensure it reads and transmits the correct pH values.
Adjustments: Make any necessary adjustments to the calibration or configuration settings.
6. Final Checks:
Secure Connections: Double-check all electrical connections to ensure they are secure and properly insulated.
Environmental Conditions: Verify that the installation can withstand the expected environmental conditions (e.g., temperature, humidity).
7. Documentation:
Record Settings: Document the configuration settings and any adjustments made during installation.
Maintenance Schedule: Establish a maintenance schedule to periodically check the transmitter and sensor for proper operation.
6. Troubleshooting
Troubleshooting pH Transmitter Issues
1. No Signal or Display:
Check Power Supply: Ensure the transmitter is receiving power. Verify voltage and connections.
Inspect Connections: Check all wiring and connections for tightness and proper insulation.
Fuse and Circuit Breaker: Inspect and replace any blown fuses or tripped circuit breakers.
2. Inaccurate Readings:
Calibration: Recalibrate the transmitter using fresh buffer solutions.
Temperature Compensation: Ensure temperature compensation is enabled and functioning correctly.
Sensor Condition: Check the pH sensor for contamination or damage. Clean or replace if necessary.
3. Drifting or Erratic Readings:
Electrical Noise: Ensure the transmitter is not affected by electrical noise from nearby equipment.
Environmental Conditions: Verify the transmitter is operating within the specified temperature and humidity range.
Sensor Hydration: Ensure the pH sensor is properly hydrated and stored in the recommended solution.
4. Stable Readings in Low Conductivity Solutions:
High Junction Flow Rate: Use an electrode with a high junction flow rate or add potassium chloride (KCl) to enhance conductivity.
5. Unusual Noise or Vibration:
Loose Components: Tighten any loose components or fittings.
Vibration: Secure the transmitter to minimize vibrations.
Practical Tips
Regular Maintenance: Perform regular maintenance checks to ensure all components are in good condition.
Documentation: Keep detailed records of any issues and the steps taken to resolve them.
7. Maintenance
Maintenance of pH Transmitter
1. Regular Inspection:
Visual Check: Inspect the transmitter and sensor for any signs of wear, damage, or corrosion.
Connections: Ensure all electrical connections are secure and free from corrosion.
2. Cleaning:
Sensor Cleaning: Clean the pH sensor regularly to remove any buildup or contamination. Use appropriate cleaning solutions based on the type of fouling.
Transmitter Housing: Keep the transmitter housing clean and free from dust
3. Calibration:
Routine Calibration: Calibrate the transmitter periodically using standard buffer solutions (e.g., pH 4.0, pH 7.0, and pH 10.0) to ensure accurate readings.
Calibration Frequency: Follow the manufacturer's recommendations for calibration frequency, typically once a month or as needed based on the application.
4. Testing:
Functionality Test: Regularly test the transmitter to ensure it is reading and transmitting the correct pH values.
Signal Integrity: Verify the integrity of the signal to ensure there are no disruptions or inaccuracies.
5. Environmental Conditions:
Temperature and Humidity: Ensure the transmitter is operating within the specified environmental conditions.
Protection: Protect the installation from extreme conditions that could affect performance.
6. Component Replacement:
Worn Parts: Replace any worn or damaged parts, such as sensors or seals, to maintain optimal performance.
Coil Inspection: Inspect the coil for any signs of burnout or damage and replace if necessary.
7. Documentation:
Maintenance Records: Keep detailed records of all maintenance activities, including inspections, cleanings, tests, and replacements.
Settings: Document the transmitter settings and any adjustments made during maintenance.
8. Manufacturer Guidelines:
Follow Instructions: Adhere to the manufacturer's maintenance guidelines and recommendations for best results.
Support: Contact the manufacturer for support if you encounter persistent issues.
8. Default Configuration
PH transmitter has the default configuration. The user can change the configuration on the wireless transmitter so that the complete sensor (transducer + wireless) delivers the proper output value.