QDx50A Pressure Sensor/Transducer Transmitter User Manual

1. Introduction

The QDx50A digital display pressure transmitter utilizes a diffused silicon pressure core as its sensitive component. It features a built-in processing circuit that converts the sensor's millivolt signal into standard voltage or current signal output. Equipped with a digital display function, it allows for quick and intuitive monitoring of on-site pressure fluctuations, minimizing interference and errors caused by signal transmission.

This device is widely used in industrial automation equipment support, as well as in petroleum, chemical, metallurgy, power, and other control fields. It is designed for high accuracy measurement and is suitable for all applications in process control, laboratory, and materials testing equipment.

2. Specifications

The QDx50A pressure transmitter offers various configurations. The default specifications for this product link are LED display, 4-20mA or RS485 output, 24VDC power supply, and M20*1.5 thread size. Customization options are available for measuring range, output signal, power supply, and thread size.

General Product Parameters:

Image: Dimensions of different pressure transmitter configurations, showing variations in length and connection types.

Image: Detailed dimensions of the QDx50A model, indicating a length of 186mm and a diameter of 51mm for the digital display housing, with an M20*1.5 pressure connection.

Image: Exploded view of the pressure transmitter, highlighting components such as the PVE engineer plastic flame retardant housing, pure copper core, diffused silicon core components, high strength adhesive, anti-damping design, and digital display. Key features include 8ms instantaneous response, 0.2%FS high precision, linearity <0.01%FS, and stability ≥10 years.

3. Setup and Installation

3.1. Wiring Instructions

The electrical connection uses a Hirschmann structural connection. Follow the diagrams below for proper wiring based on the output signal type.

Image: Detailed wiring diagrams for the pressure transmitter. Includes 2-wire current output (4-20mA), 3-wire voltage output (0-5V, 0-10V, 1-5V), and 4-wire RS485 output. Pin assignments are clearly labeled (e.g., PIN1: Positive Pole, PIN2: Signal, PIN3: COM, PC A, PC B).

Wiring Procedure for Hirschmann Connector:

1. Unscrew the Phillips head M3 screw.
2. Unplug the plastic insert.
3. Use a flat screwdriver to insert into the disassembly slot and pry out the terminal block.
4. Thread the shielded cable into the outlet hole part.
5. Wire according to the wiring diagram at the terminal on the back of the terminal block.
6. After wiring is completed, the direction in which the terminal block is installed can be changed.
7. Ensure that the outer diameter of the cable used is within the range allowed by the ferrule and that the cable is securely and gap-free in the ferrule.
8. Install the socket correctly and properly to ensure the specified level of protection.

3.2. Installation Considerations

• Warning! Installation must be carried out without pressurization and without power supply.
• Warning! The transmitter must be installed by a technician who reads and understands this operation manual.
• Dangerous! To avoid the risk of explosion, observe the following rules:
1. When there is a risk of explosion, it is forbidden to operate the transmitter in the power supply state, except when an intrinsically safe circuit is connected.
2. Whether or not it is in the explosion danger area, ensure that the entire line is in an equal potential protection state.
3. If there is a possibility of lightning strike or overpressure damage, lightning protection measures against overpressure must be taken.
4. Ensure that the connection between each intrinsically safe transmitter also meets the intrinsic safety requirements. The operator must ensure the intrinsic safety of the entire system.
5. Excessive dust deposition (more than 5mm) or complete coverage of dust on the surface of the transmitter must be avoided.
6. The intrinsically safe explosion-proof system must be formed with associated equipment that has passed explosion-proof certification before it can be used in an explosion-proof gas environment. The wiring of the system shall comply with the requirements of the instruction manual of the transmitter and the associated equipment at the same time, and the terminal shall not be connected incorrectly.
7. Maintenance can only be carried out when the installation site confirms that no flammable gas exists.
8. The connection cable between the product and the associated equipment should be a shielded cable with an insulating sheath, and its shielding layer should be grounded in a safe place.
• Dangerous! The transmitter adopts a diffused silicon oil-filled core. Improper use will cause explosion accidents. To ensure safety, it is strictly forbidden to measure oxygen.
• Warning! It is forbidden to measure media that are incompatible with the transmitter.
• When receiving the product, please check whether the packaging is intact, and verify that the transmitter model and specifications are consistent with your purchase.
• To avoid damage to the diaphragm, please unpack the protective cap of the box before activating the device. Keep the protective cap that comes with the product; immediately after the device is removed, put a protective cap on the pressure connection. Use extreme caution when handling unprotected diaphragms, as they are very sensitive and can be easily destroyed.
• Do not use brute force when installing the transmitter.
• For pressures less than 0.03MPa, vertical installation is recommended to avoid affecting measurement accuracy. Otherwise, it can be installed at any angle on the measurement point. If the interface size does not match the field interface, a self-made replacement connector can be used.
• In hydraulic systems, pay attention to the installation of the pressure interface (convenient for gas discharge).
• If the pressure interface is upward or lateral when the transmitter is installed, ensure that no liquid flows into the equipment housing, otherwise moisture and dirt will block the atmospheric port near the electrical connection, potentially causing equipment failure. The threaded edges of the electrical connection must be kept free of dust and dirt.
• Try to install in locations where the temperature gradient change is small.
• If the transmitter is installed in a harsh site and encounters dangerous damage such as lightning strike or overvoltage, it is recommended to protect against lightning and overvoltage between the distribution box or power supply and the transmitter.
• When measuring steam or other high-temperature media, ensure that the medium's temperature does not exceed the transmitter's operating temperature. If necessary, a cooling device must be installed.
• During installation, a pressure shut-off valve should be installed between the transmitter and the medium to facilitate maintenance and prevent the pressure intake from being blocked, which could affect measurement accuracy.
• During the installation process, the transmitter should be tightened from the hexagonal nut at the bottom of the equipment with a wrench to avoid directly rotating the upper part of the equipment and causing the connection line to be disconnected.
• This product is a weak current device. When wiring, it should be separated from strong electrical cables and routed in accordance with relevant national wiring standards (GB/T50312-2016).
• Ensure that the power supply voltage meets the power supply requirements of the transmitter. Make sure that the upper pressure of the pressure source is within the range of this transmitter.
• In the process of pressure measurement, pressure should be slowly applied and relieved to avoid instantly adding high pressure or falling to low pressure.

4. Operation

Once properly installed and wired, the QDx50A pressure transmitter will continuously measure the pressure of the medium. The integrated LED digital display provides real-time pressure readings. For models with 4-20mA, 0-5V, 1-5V, 0-10V, or RS485 output, the signal can be directly connected to a computer interface card, control instrument, intelligent instrument, or PLC for data acquisition and control.

The digital display allows for direct visual confirmation of the measured pressure. No specific user interaction is typically required during normal operation beyond initial setup and monitoring.

5. Maintenance

• Warning! When disassembling the transmitter, ensure it is disconnected from the pressure source and power supply to avoid accidents caused by media spraying.
• Do not disassemble the product yourself during use. Avoid touching the diaphragm, as this may cause product damage.
• Regularly inspect the electrical connections and cable for any signs of wear, damage, or loose connections.
• Keep the transmitter's exterior clean and free from excessive dust or dirt, especially around the atmospheric port and electrical connections, to maintain its IP65 protection rating.
• If used in corrosive environments, periodically check the stainless steel housing for any signs of corrosion.
• Ensure the pressure connection remains free of blockages.
• If a cooling device is installed for high-temperature media, ensure it is functioning correctly.

6. Troubleshooting

This section provides general troubleshooting steps. For complex issues, contact technical support.

• No Display/Incorrect Reading:
  • Check power supply voltage to ensure it meets the 12-36VDC requirement.
  • Verify all wiring connections are secure and correct according to the wiring diagrams.
  • Ensure the pressure source is within the specified measuring range of the transmitter.
  • Check for any physical damage to the sensor or display unit.
• No Output Signal (4-20mA, Voltage, RS485):
  • Confirm power supply is active and correct.
  • Inspect output signal wiring for breaks or incorrect connections.
  • Verify the receiving instrument (PLC, control system) is correctly configured to read the expected signal type.
• Unstable Readings:
  • Check for pressure fluctuations in the medium.
  • Ensure the transmitter is securely installed and not subject to excessive vibration.
  • Verify the medium temperature is within the operating range.
  • Check for any air bubbles or blockages in the pressure line.
• Explosion Hazard Warnings:
  • Immediately disconnect power if operating in an explosion-risk area without proper intrinsic safety measures.
  • Never measure oxygen with this device due to the oil-filled core.
  • Ensure the entire system is in an equal potential protection state in hazardous environments.

7. User Tips

• For optimal accuracy, especially with low pressures (<0.03MPa), consider vertical installation.
• Always use a wrench on the hexagonal nut at the bottom for tightening during installation to prevent damage to internal wiring.
• When dealing with high-temperature media like steam, always install a cooling device to protect the transmitter.
• Implement a shut-off valve between the transmitter and the medium for easier maintenance and to prevent blockages.
• Handle the diaphragm with extreme care, as it is very sensitive and easily damaged. Always replace the protective cap when the device is not in use.

8. Certifications and Support

The QDx50A pressure transmitter has received the following certifications, ensuring compliance with international standards:

• CE Certification
• FCC Certification
• RoHS Compliance
• ISO Certification
• Patent
• CNEX Ex (Explosion Proof)
• NEPSI Ex (Explosion Proof)

Image: Display of various enterprise and product certifications, including Business License, SGS, CE, ECM, CMA, RoHS, ISO, Patent, CNEX Ex, and NEPSI Ex.

For further assistance, technical support, or warranty inquiries, please contact the manufacturer or your local distributor. A detailed user manual in PDF format is also available for download: User Manual (PDF).