Before Purchasing a Baoji Maike Differential Pressure Transmitter, First Clarify the Key Verification Items

When purchasing a Baoji Maike differential pressure transmitter, the measuring range is only a basic parameter and should not be the sole criterion. Differential pressure transmitters are commonly used for filter blockage monitoring, air pressure measurement, level conversion, flow measurement, furnace negative pressure, cleanroom differential pressure, and chemical process control. Different applications may require completely different sensor structures, overload capacities, diaphragm materials, and output protocols.

Purchasing personnel should first confirm the measured medium with on-site equipment, process, or automation personnel: whether it is air, steam, water, oil, or a corrosive, viscous, crystallizable, or particle-containing medium. The medium properties directly affect wetted materials, pressure tapping methods, isolation diaphragms, and anti-clogging solutions. Purchasing based solely on the original appearance can easily result in zero drift, blockage, or corrosion failure after installation.

It is also necessary to clarify the role of the differential pressure transmitter in the control system: whether it is only used for local display and interlock alarms, or participates in PID control. If the signal is sent directly to a PLC, DCS, or remote monitoring platform, the output type, power supply, communication protocol, and alarm logic must be verified at the same time to prevent the sensor from operating normally while the system cannot correctly read the data.

When providing supporting services for sensors and transmitters, Xi'an Shenghongchuang Instrumentation Co., Ltd. can organize selection information according to on-site operating conditions. For Baoji Maike differential pressure transmitter procurement projects, it is recommended to submit the original model, nameplate photos, process conditions, and control system requirements together to reduce configuration deviations caused by relying only on the name or verbal descriptions.

Step 1: Verify Measuring Range, Static Pressure, and Overload Capacity

The Measuring Range Should Cover the Normal Operating Range

The differential pressure range should be determined according to the actual differential pressure range, rather than simply selecting a larger range. Under normal circumstances, the operating differential pressure should preferably fall within 30% to 80% of the transmitter range, ensuring both resolution and allowance for operating fluctuations. For example, if the normal filter differential pressure is 5 kPa and the blockage alarm value is 15 kPa, products with a range of 0 kPa to 20 kPa or 0 kPa to 25 kPa may be prioritized.

If the selected range is too large—for example, if the actual differential pressure is only 2 kPa but a sensor with a range of 0 kPa to 100 kPa is configured—the output signal variation will be compressed, affecting both control system display accuracy and alarm assessment. Conversely, if the range is too small, it may be exceeded during startup impact, valve switching, or filter element blockage, resulting in measurement distortion or even damage to sensitive components.

The purchase order should distinguish between the “differential pressure range” and the “allowable pressure on one side.” A differential pressure transmitter measures the pressure difference between the high-pressure side and low-pressure side, but both sides may simultaneously be subjected to high system static pressure. For example, when measuring a 10 kPa differential pressure on a 1 MPa pipeline, the key concern is not only the 10 kPa range, but also whether the allowable operating static pressure of the product reaches 1 MPa or higher.

For applications with significant pressure fluctuations on both sides, unidirectional overload and bidirectional overload ratings must also be verified. In some operating conditions, transient reverse pressure between the high- and low-pressure sides may occur during start-up, shutdown, purging, or incorrect operation. If the product has insufficient bidirectional pressure resistance, diaphragm deformation, zero shift, or irreversible damage may occur even when the normal operating range is properly matched.

Accuracy, Stability, and Response Time Must Not Be Confused

Accuracy generally refers to the allowable error between the transmitter output and the actual differential pressure. The overall accuracy, nonlinearity, repeatability, and hysteresis specified in the manual should be reviewed. For general filter monitoring, Class 0.5 products may meet application requirements; for metering, critical interlocks, or high-precision air flow control, Class 0.25 or even higher-accuracy configurations should be selected according to project specifications.

Long-term stability reflects the drift level of a sensor after continuous operation. When purchasing, do not only consider factory accuracy; also pay attention to zero stability after long-term use, especially in environments with high temperature, vibration, pressure pulsation, or significant day-to-night temperature variations. Poor stability increases subsequent calibration frequency and may also lead to false alarms and maintenance costs.

Response time determines how quickly the transmitter tracks differential pressure changes. Ventilation systems, gas pipelines, and fast interlock applications are generally more sensitive to response; tank level measurement and slow filtration processes may place greater emphasis on stable output. If obvious pulsation is present on site, confirm whether damping settings, buffering devices, or software filtering are required to prevent frequent fluctuations in displayed values.

It is recommended to retain the product certificate, calibration records, range labels, and wiring instructions during acceptance. For batch procurement projects, zero point, full-scale output, and repeatability may be sampled and inspected, with key points verified within the 4 mA to 20 mA output range to ensure that the range, wiring terminals, and installation orientation of equipment from the same batch are consistent.

Step 2: Verify Sensor Structure and Medium Compatibility

Wetted Materials Must Match the Measured Medium

The wetted parts of a differential pressure transmitter include the diaphragm, process connection, seals, and pressure tapping sections. Common stainless steel materials offer good compatibility with water, air, general oils, and ordinary industrial media. However, when handling acid or alkali solutions, chloride-containing media, high-salt-spray environments, or special solvents, 316L stainless steel, Hastelloy, tantalum, fluororubber, or other corrosion-resistant configurations must be confirmed based on the medium composition.

Purchasing personnel should request the medium name, concentration, temperature, pressure, and whether it contains solid particles from the user. Descriptions such as “acidic liquid,” “wastewater,” or “chemical liquid” alone are generally insufficient for reliable selection, because the corrosiveness of similar media toward metal diaphragms and sealing materials may differ significantly with changes in concentration and temperature.

For high-viscosity, easily crystallized, easily solidified, or fiber-particle-containing media, ordinary pressure tapping holes may become blocked. In such cases, priority should be given to confirming flush diaphragm structures, flange mounting, flushing connections, diaphragm seals, or capillary remote transmission solutions, so that pressure can be stably transmitted to the sensor instead of allowing deposits to remain in the pressure tapping port for extended periods.

For steam, high-temperature oils, or high-temperature gas applications, the medium temperature must also be confirmed. Even if the pressure is within the allowable range, temperatures exceeding the permitted limits of the sensor wetted parts or electronics chamber will accelerate seal aging and affect the zero point. Where necessary, condensate bends, cooled impulse lines, heat-dissipating installation, or remote diaphragm seals may be used to reduce heat transfer.

Confirm the Sealing Method and Process Connection Item by Item

The process connection should not simply be specified as a “threaded connection”; the connection size and standard must be clearly stated, such as M20×1.5, G1/2, or NPT1/2. Different threads vary in thread profile, sealing method, and installation dimensions. Incorrect connections may result in installation failure, thread damage, or long-term leakage.

Common pressure connections for differential pressure transmitters also include dual ports, three-valve manifold assemblies, flange connections, and sanitary connections. When used for level measurement, confirm where the high- and low-pressure sides are connected respectively; when used for air pressure measurement, confirm whether pressure nozzles, Pitot tubes, or air duct mounting accessories are included. Interface matching affects not only installation, but also whether the measurement direction is correct.

The seal material must not be overlooked either. Standard seals can be used in room-temperature water and air environments, but in high-temperature, oil, corrosive medium, or vacuum applications, the temperature resistance, medium resistance, and aging resistance of the sealing rings must be confirmed. The sealing material should be listed as a specific configuration in the procurement list and should not be generally replaced by “standard sealing.”

Before installation, the high-pressure and low-pressure side markings should also be verified. After reverse connection, the 4 mA to 20 mA signal may change in the opposite direction, leading to incorrect filter blockage alarms, fan control, or level conversion results. For products with displays, the display direction and system variable direction can be verified using a small differential pressure range before commissioning.

Step 3: Verify Output Signal, Power Supply, and Control System

Confirm Analog Signals, Communication Methods, and Wiring Conditions

The most common output method in industrial sites is two-wire 4 mA to 20 mA. Its advantages include strong interference resistance, long transmission distance, and convenient connection to PLCs, DCSs, and intelligent digital display control instruments. When purchasing, confirm whether the existing system input card is current-type or voltage-type to avoid connecting a 4 mA to 20 mA product to a 0 V to 10 V interface and causing signal mismatch.

If the control system requires remote parameter setting, device diagnostics, or multi-point networking, further confirm whether RS485, Modbus, HART, or other digital communication functions are needed. Identical communication protocol names do not mean that all parameters are completely the same; baud rate, address settings, register definitions, master station compatibility, and on-site commissioning conditions should also be verified.

The supply voltage must be consistent with the on-site power supply. A common DC supply is 24 VDC, but the actual available range, load resistance, and line voltage drop must still be confirmed. When the transmission distance is long or safety barriers or power distributors are connected in series, the available loop voltage will decrease. Before purchasing, verify the power supply capacity and input module requirements to prevent the output from failing to reach 20 mA steadily.

In hazardous areas, ordinary enclosures cannot be used in place of explosion-proof products. Intrinsically safe, flameproof, or other protection configurations should be confirmed according to site classification and project requirements. Explosion-proof markings, cable sealing glands, safety barrier parameters, and grounding requirements must also be checked. Explosion-proof certificates, factory documentation, and on-site installation specifications should form a complete chain.

Display, Alarm, and Control Functions Should Be Selected According to Application Requirements

Differential pressure transmitters with digital displays facilitate on-site inspection and are suitable for applications where equipment maintenance personnel need to quickly check differential pressure. However, display units should be consistent with process conventions, such as Pa, kPa, MPa, mmH2O, or mbar, to avoid misjudging equipment conditions due to mixed units within the same workshop.

If direct on-site alarming or control is required, verify whether relay outputs, upper and lower limit settings, hysteresis settings, and password protection are configured. Alarm values should not simply be set near full scale, but should be determined based on the allowable process range and actual equipment operating data. For example, filter element blockage alarms may be set with reference to the initial differential pressure, maximum allowable differential pressure, and maintenance cycle.

For projects requiring only remote transmission signals, there is no need to add excessive functions, as this may increase procurement costs and subsequent maintenance complexity. For projects requiring local display, interlocks, historical data, or remote diagnostics, the functional boundaries among the instrument, control cabinet, and host system should be confirmed in advance to avoid unclear responsibilities.

Xi'an Shenghongchuang Instrumentation Co., Ltd. can provide differential pressure transmitters, intelligent digital display control instruments, and related supporting products. Verifying sensors together with display instruments, control modules, and on-site installation accessories during procurement helps reduce inconsistencies in range, signal, and power supply among different devices.

Step 4: Verify Installation Environment, Documentation, and Incoming Inspection

Environmental Conditions Determine the Enclosure and Installation Solution

The installation environment must specify requirements for temperature, humidity, dust, vibration, electromagnetic interference, and protection rating. Requirements differ among areas near ordinary indoor control cabinets, outdoor exposed locations, washdown areas, damp pump rooms, and locations adjacent to high-vibration equipment. Particular attention should be given to whether the enclosure material, protection rating, cable interface, and mounting bracket are suitable.

When installed near high-power motors, variable-frequency drives, or high-power switching equipment, signal cables should be properly shielded and routed. Even if a differential pressure transmitter has a certain level of interference resistance, reading fluctuations may still occur if signal cables run parallel to power cables over long distances. Shielded cables, grounding methods, and isolation module requirements may be confirmed during procurement.

The installation location should facilitate venting, draining, maintenance, and calibration. When measuring liquid differential pressure, avoid gas accumulation in impulse lines as much as possible; when measuring gas differential pressure, avoid liquid accumulation; when measuring steam, ensure consistent condensation conditions. Improper handling of installation details often prevents a qualified sensor from obtaining stable data.

For outdoor or low-temperature areas, sun protection, rain protection, frost protection, and heat tracing requirements must also be considered. In particular, for water-containing or easily solidified media, freezing or crystallization in impulse lines will prevent the differential pressure from being transmitted accurately. When purchasing sensors, the pressure tapping lines and insulation measures should be evaluated at the same time.

Conduct Incoming Inspection Item by Item According to the Nameplate and Documentation

After receiving a Baoji Maike differential pressure transmitter, first verify whether the nameplate model, range, output signal, power supply, accuracy, process connection, wetted material, and protection rating are consistent with the purchase contract and technical confirmation sheet. For products of the same model with multiple configuration codes, do not determine that they have the same configuration solely based on similar enclosures.

Then inspect the product appearance, connection threads, display, wiring terminals, seals, and supplied accessories to confirm that there is no transportation damage, no connection deformation, and no signs of looseness or water ingress. For batch products, it is recommended to arrange them by equipment tag number and retain the corresponding certificates, manuals, and calibration documentation for convenient subsequent installation and traceability.

Before energizing, the zero output may be checked according to the manual. For standard 4 mA to 20 mA products, the output should be close to 4 mA under zero differential pressure. After commissioning, use a standard pressure source or on-site comparison method to verify several key points, focusing on zero point, full scale, repeatability, and signal stability; measurement points involving safety interlocks should be included in the system joint commissioning records.

When purchasing a Baoji Maike differential pressure transmitter, it is recommended to organize operating condition parameters, original instrument documentation, installation interface photos, and system signal requirements into a verification checklist and submit it to the technical personnel of Xi'an Shenghongchuang Instrumentation Co., Ltd. for configuration confirmation. Placing the order after confirming the range, static pressure, material, interface, output, and installation accessories can enable the sensor to maintain more stable and reliable measurement performance under actual operating conditions.