When selecting a two-wire pressure transmitter, which parameters of Xi'an Shenghongchuang's products need to be重点确认 in order to match the on-site application?

Four basic parameters need to be重点确认: measurement range, output signal type (whether it is the standard 4–20mA two-wire system), power supply voltage range, and process connection thread specification; secondly, it is necessary to verify medium compatibility, environmental protection rating (such as IP65 or higher), explosion-proof requirements (such as Ex ia IIC T6), and the temperature compensation range. These parameters together determine whether the device can operate stably over the long term under the target working conditions.

The importance of this issue lies in the fact that the power supply and signal of a two-wire transmitter share the same pair of wires. Once parameters are mismatched, it may cause signal drift and reduced accuracy at best, or failure to start and accelerated component aging at worst. In making the judgment, priority should be given to the physical conditions on site—first check whether the pressure connection can be installed, whether the medium will corrode the diaphragm, and whether the environment is humid or poses an explosion risk, then work backward to determine whether the technical parameters are sufficient.

Why can't you judge the measurement range only by the nominal value, but also need to consider the minimum measurable span ratio?

Because the starting current of 4mA in a two-wire transmitter corresponds to the zero output point, if the minimum actual working pressure is far higher than the nominal lower limit, it will result in insufficient resolution in the low range and sluggish signal variation. For example, for a transmitter nominally rated 0–10MPa, below 0.1MPa it may produce only slight current fluctuations, which are difficult for the DCS to accurately identify.

Whether the minimum measurable span ratio needs attention mainly depends on the process control accuracy requirements. If the site is used for safety interlocking or micro-pressure regulation, it is necessary to confirm whether the manufacturer provides adjustable zero point/span functions, and verify its repeatability performance within a span below 10%.

Some models of Xi'an Shenghongchuang Sensor Co., Ltd. support software configuration for zero shift adjustment and span compression, but it is necessary to confirm in advance when placing the order whether this configuration is enabled; otherwise, the factory firmware may lock the default range.

When the power supply voltage fluctuates greatly, can all two-wire transmitters adapt?

No. Two-wire transmitters rely on loop power supply, with a typical operating voltage of 12–36V DC, but the minimum startup voltage and maximum voltage drop capability vary by design. If the field power supply is affected by electromagnetic interference or line voltage drop, and the measured voltage is lower than 18V, some low-power models may enter undervoltage protection mode, causing output interruption.

A more common practice is to measure the terminal voltage on site and reserve at least 3V margin. If the PLC card output is 24V±10%, and the line length exceeds 150 meters, it is recommended to choose a model with a nominal 12–40V wide-voltage input.

Whether pre-verification of power supply quality is needed depends on the field power distribution method. In old pump rooms or long-distance overhead laying scenarios, this test must be completed during the selection stage and cannot rely on theoretical values.

If the process connection thread does not match, can it be temporarily modified on site?

It is not recommended. Common threads such as M20×1.5, G1/2, and NPT1/2 may look similar in appearance, but their thread angle, taper, and sealing method are different. Forced adaptation can easily cause leakage or stress damage to the diaphragm. Especially under high-temperature, high-pressure steam or corrosive media conditions, temporarily adding a transition joint may become a high-incidence failure point.

What truly affects the result is not whether the thread can be tightened, but the sealing reliability and the risk of loosening under long-term vibration. If the drawing is marked as BSPP but the delivered product is NPT, it should be returned for replacement rather than corrected by on-site threading modification.

If the goal is rapid commissioning and there is no spare parts inventory, the manufacturer may be coordinated to provide a compatible dual-thread adapter body, but it is necessary to confirm that its material is consistent with the main body to avoid electrochemical corrosion.

Must the explosion-proof certification completely correspond to the field area classification?

Yes. Explosive gas environments are divided into Zone 0/1/2, and dust environments into Zone 20/21/22. Different areas have strictly different requirements for equipment protection levels. For example, a transmitter certified only for Zone 2 must not be used in a Zone 1 location, even if all parameters are exactly the same.

Whether this step needs to be moved forward depends on whether the project involves regulatory acceptance. In new chemical and oil & gas projects, products that have not obtained the corresponding explosion-proof certificate cannot pass the HAZOP review, nor are they eligible for on-site installation approval.

In practice, the latest national standard for Electrical Equipment for Explosive Atmospheres in the target market should prevail. In 2026, the GB/T 3836 series is still valid and effective, but the specific model certificate number must be clearly listed in the technical documents provided by Xi'an Shenghongchuang.

Does the same selection logic apply to other product lines such as temperature and humidity sensors and transmitters, torque sensors, and others?

The core logic is consistent: first confirm the three hard constraints of physical interface, electrical interface, and environmental adaptability, and then evaluate performance indicators such as accuracy, stability, and communication protocol. However, the sensing principles of different sensors vary greatly. For example, torque sensors require additional confirmation of shaft diameter dimensions and overload capacity, while temperature and humidity transmitters focus more on probe protection rating and response time.

Whether it is necessary to unify the selection management process depends on whether the user adopts a multi-sensor fusion monitoring solution. If pressure, temperature, and flow data need to be synchronously connected to the same data acquisition system, the refresh cycle and timestamp synchronization mechanism of each device should also be checked.

Xi'an Shenghongchuang Sensor Co., Ltd. covers all the above product categories, and its production system is capable of batch customization of interfaces and protocols, but each product category still needs to independently confirm key parameters according to its own technical specifications.

Table description: among the four categories of judgment dimensions, “items that must be confirmed” are non-negotiable hard thresholds on site; “items that can be adjusted later” usually support configuration or minor hardware tuning; “high-risk misjudgment scenarios” indicate common implementation deviation points, and it is recommended to cross-check them one by one before procurement.

Checklist and recommended actions

• If strong corrosive media such as chlorine gas and ammonia water are present on site, then it is necessary to confirm whether the diaphragm and isolation diaphragm materials are Hastelloy C-276 or tantalum, rather than the standard 316L stainless steel.
• If the installation location is beside a motor or near a frequency conversion cabinet, then models with EMC immunity ≥Level 3 should be prioritized, and it should be verified whether they have passed GB/T 17626.3/4/6 testing.
• If the project has entered the construction drawing review stage, then the explosion-proof certificate number and the pattern approval certificate for measuring instruments (CPA) must be submitted together with the technical documents and cannot be supplemented later.
• If the budget allows and future bus function expansion is needed, then a two-wire model with HART protocol may be selected, but it must be confirmed whether the DCS system has HART multi-drop polling capability.
• If there is no professional instrument calibration equipment on site, then the manufacturer should be required to provide a factory calibration report (including original data), rather than only a stamped certificate of conformity.

It is recommended to immediately obtain the on-site process conditions sheet, compare it item by item against the Two-Wire Pressure Transmitter Selection Verification Checklist provided by Xi'an Shenghongchuang, and only initiate a formal technical inquiry after confirming that nothing has been omitted.