Xi 'an Qinwei Instrument Factory (General Partnership Enterprise)
| Payment Terms | T/T,D/P,D/A,L/C |
| Supply Ability | 100PCS/Month |
| Delivery Time | 5-8 work days |
| Packaging Details | Carton |
| Range | 0 ~ 1-300MPa |
| Usage | Industrial |
| Measurement Range | 0 to 1000 psi |
| Stability | <0.1%/year |
| Output Load | ≤ 500 Ω |
| Output | 4~20mA/0.5-4.5V/0-5V/1-5V |
| Operating Temperature | -40 to 85 °C |
| Protocol | hart |
| Voltage | 5±0.5VDc |
| Relative Humidity | 5~98%RH |
| Brand Name | QINWEIYB |
| Model Number | QWYB-520 |
| Certification | Explosion-proof certificate ，Safety certificate |
| Place of Origin | China |
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Product Specification
| Payment Terms | T/T,D/P,D/A,L/C | Supply Ability | 100PCS/Month |
| Delivery Time | 5-8 work days | Packaging Details | Carton |
| Range | 0 ~ 1-300MPa | Usage | Industrial |
| Measurement Range | 0 to 1000 psi | Stability | <0.1%/year |
| Output Load | ≤ 500 Ω | Output | 4~20mA/0.5-4.5V/0-5V/1-5V |
| Operating Temperature | -40 to 85 °C | Protocol | hart |
| Voltage | 5±0.5VDc | Relative Humidity | 5~98%RH |
| Brand Name | QINWEIYB | Model Number | QWYB-520 |
| Certification | Explosion-proof certificate ，Safety certificate | Place of Origin | China |
| High Light | High Precision Pressure Transmitter ，Precision Pressure Transmitter Hart Protocol ，Hart Protocol Pressure Transmitter | ||
Semiconductor-based pressure sensors—piezoresistive, capacitive MEMS—achieve excellent accuracy under normal operating conditions. But certain environments attack semiconductors at a fundamental level: gamma radiation in nuclear plants creates electron-hole pairs that degrade junction performance; extreme EMI from arc furnaces saturates microvolt-level bridge signals; and prolonged exposure to 150°C+ temperatures accelerates dopant diffusion in silicon.
The inductive (LVDT-based) pressure transmitter circumvents these vulnerabilities by replacing the semiconductor sensing element with a purely electromagnetic transducer. At its core, an LVDT (Linear Variable Differential Transformer) measures the minute displacement of a pressure-responsive diaphragm or bourdon tube through changes in magnetic coupling between transformer windings. There are no semiconductors in the sensing path—just copper wire, magnetic cores, and mechanical elements that are fundamentally immune to radiation damage, electromagnetic interference, and high-temperature degradation of semiconductor junctions.
Pressure-to-displacement conversion: Process pressure acts on a diaphragm, bellows, or bourdon tube. The resulting mechanical displacement—typically 0.1-2 mm at full scale—is transmitted to the magnetic core of an LVDT via a precision linkage.
LVDT displacement sensing: The LVDT consists of one primary coil and two secondary coils wound symmetrically on a cylindrical former. An AC excitation signal (typically 1-10 kHz, 1-5 Vrms) applied to the primary coil induces voltages in both secondary coils. The movable magnetic core—linked to the pressure-sensing element—changes the magnetic coupling between primary and secondaries. At the null position, both secondary voltages are equal; as the core displaces, one secondary voltage increases while the other decreases. The differential voltage (V_sec1 − V_sec2) is linearly proportional to core displacement over a specified stroke range.
Signal conditioning: A synchronous demodulator converts the AC differential voltage to a DC signal proportional to displacement (and therefore pressure). Modern transmitters digitize this DC signal, apply microprocessor-based linearization and temperature compensation, and output a standardized 4-20 mA + HART signal. The sensor section (LVDT) requires the AC excitation supply; the electronics section operates from the standard 4-20 mA loop power.
Ruggedness factors: LVDT sensors are inherently frictionless (no contact between core and coil former), have theoretically infinite resolution (limited only by the demodulator electronics), and tolerate extreme shock, vibration, and temperature because the sensing element is a passive electromagnetic device with no bonded strain gauges or microscopic silicon structures to fatigue or fracture.
Industry: Nuclear Power Generation
Application: Containment building internal pressure monitoring for accident management and post-LOCA (Loss of Coolant Accident) pressure tracking
Medium: Air/steam mixture, potential post-accident radiation field
Pressure Range: 0-5 bar(a)
Radiation Environment: Normal operation: <0.01 Gy/h; post-accident: up to 10⁴ Gy/h design basis
Customer Challenge: Safety-related (Class 1E) qualification requires the transmitter to maintain specified accuracy during and after a design-basis accident, including exposure to steam, radiation, and chemical spray. Semiconductor-based transmitters derate or fail under combined radiation-temperature conditions beyond qualified limits.
Solution: LVDT-based pressure transmitter with radiation-qualified electronics, Class 1E certified per IEEE 323/344. Mechanical core sensor with no semiconductor junctions in the measurement path. Electronics housed in a shielded compartment with radiation-tolerant components.
Result: Equipment qualification testing demonstrated accuracy within ±0.5% throughout the 30-day post-accident profile with 10⁵ Gy cumulative dose. Qualification renewed for plant license extension. No radiation-related drift observed in 15 years of service.
Industry: Steel Manufacturing
Application: Continuous caster mold oscillation hydraulic pressure monitoring
Medium: Fire-resistant hydraulic fluid (phosphate ester)
Pressure Range: 0-300 bar
Environment: 50-80°C ambient, 5-20 g vibration at mold oscillation frequency (1-5 Hz), strong magnetic fields from nearby 5000A DC casting current, airborne steel dust
Customer Challenge: Piezoresistive transmitters failed within 3-6 months—vibration fatigue of wire bonds, DC magnetic fields saturating signal conditioning amplifiers, and conductive dust ingress through breather vents. Each failure caused mold oscillation to revert to open-loop control, risking breakout (molten steel escaping the mold).
Solution: Fully sealed LVDT-based pressure transmitter with IP68-rated welded stainless steel housing. No breather/vent (absolute pressure reference). Shielded cable with twisted-pair signal wiring. Magnetic field immunity verified to 100 mT (1000 Gauss).
Result: Transmitter service life extended to 4+ years with zero vibration or EMI-related failures. Breakout incidents decreased 80% due to reliable closed-loop pressure control. Spare inventory reduced from 12 to 3 units per caster.
LVDT sensors offer superior environmental ruggedness (radiation, vibration, EMI tolerance) and have no bonded interfaces that can fatigue under cyclic loading. Their frictionless operation eliminates the hysteresis associated with mechanical linkages in bonded strain gauge designs. However, LVDT sensors are physically larger, heavier, and more expensive than semiconductor strain gauges due to the precision-wound transformer coils and magnetic core assemblies. The excitation requirement (AC supply for the LVDT primary) adds complexity compared to DC-excited strain gauge bridges. For general industrial applications, strain gauge sensors provide the best cost-performance ratio. LVDT sensors are selected when the operating environment would degrade or destroy strain gauge sensors—radiation fields, extreme sustained vibration, or very wide temperature cycling.
Yes—significantly. The LVDT sensor itself is analog, but the HART digital overlay (superimposed on the 4-20 mA signal) enables: remote configuration of range, damping, and engineering units without accessing the transmitter; device diagnostics including sensor coil impedance monitoring (detecting winding degradation before failure); multi-variable output (pressure + sensor temperature); and integration with asset management systems for predictive maintenance. The HART protocol modernizes the LVDT transmitter's interface without altering its fundamentally robust sensing principle—you get the environmental ruggedness of electromagnetic sensing with the digital connectivity of a smart instrument.
Industry: Aerospace / MRO (Maintenance, Repair, Overhaul)
Application: Hydraulic system pressure measurement during landing gear actuator functional testing on a Boeing 737 MRO test stand
Medium: Skydrol LD-4 phosphate ester hydraulic fluid (fire-resistant, aggressive to many elastomers and coatings)
Pressure Range: 0-350 bar (5,000 psi)
Operating Temperature: -40°C to +120°C (fluid); test stand ambient -10°C to +50°C
Customer Challenge: The test stand cycles landing gear actuators through 5,000 test cycles at pressures from 50-300 bar with temperature varying from -40°C (cold-soak simulation) to +120°C (post-landing heat soak). The pressure measurement system must maintain ±0.5% accuracy across the full temperature range to ensure test validity. Previous strain-gauge transmitters exhibited 0.8-1.2% temperature hysteresis—output at 20°C during warm-up differed from output at 20°C during cool-down by up to 0.5% due to mechanical hysteresis in the bonded strain gauge adhesive.
Previous Problem: Temperature hysteresis caused approximately 2% of test cycles to be flagged as "out of tolerance" not because the landing gear actuator was faulty, but because the pressure measurement itself was imprecise. Each flagged test required re-running—adding 45 minutes to a 3-hour test procedure. With 80 landing gear tests per year, the false failures consumed approximately 60 hours of test stand time ($15,000 at the facility's hourly rate).
Solution: LVDT-based inductive pressure transmitter with zero mechanical hysteresis. The frictionless core movement eliminates the adhesive creep and mechanical hysteresis that plague bonded strain gauge designs during temperature cycling. 316L stainless steel wetted parts with FKM O-rings for Skydrol compatibility. 0-10V analog output to test stand DAQ with HART digital output for calibration verification.
Installation Location: Test stand hydraulic manifold, with flexible high-pressure hose connection and vibration-isolated mounting bracket.
Result: Temperature hysteresis reduced from 0.8-1.2% to <0.1%. False test failures eliminated—all 80 annual tests now pass on first run. Test stand utilization improved from 72% to 84% by eliminating re-test time. The transmitter's frictionless design also survived the high-cycle fatigue environment (5,000 cycles × 80 tests/year = 400,000 pressure cycles/year) with zero drift, whereas the previous bonded strain gauge design accumulated 0.3% drift per 100,000 cycles due to adhesive fatigue.
Industry: Marine / Shipbuilding
Application: Ballast tank level pressure measurement (hydrostatic head) for ship trim and stability control on a 180m container vessel
Medium: Seawater (ballast); oily water mixture (bilge)
Pressure Range: 0-2.5 bar(g) (corresponding to approximately 25m water column)
Installation Environment: Ship engine room and ballast tank penetrations, continuous vibration (0.5-5 mm/s at 10-200 Hz from main engine and generator sets), 100% humidity, occasional saltwater spray, ambient 5-55°C
Customer Challenge: Ballast water management is critical for vessel stability—incorrect ballast tank levels during cargo operations can cause the ship to list beyond safe limits. The 12 ballast tank level transmitters experienced an average of 2 failures per year, each requiring dry-docking or diver intervention to replace because the transmitters were mounted at the tank bottom penetration. Each failure during a voyage caused the tank to be excluded from the automated ballast control system, requiring manual level monitoring.
Previous Problem: Piezoresistive transmitters failed due to combined vibration fatigue (wire bond failures on the sensor die) and moisture ingress through breather vents (ships' engine rooms have near-100% humidity with salt aerosol). Two failures occurred during cargo operations in port, causing loading delays of 4-6 hours at $8,000/hour demurrage cost.
Solution: LVDT-based inductive pressure transmitters with fully welded hermetic stainless steel housing—no breather vent, no humidity ingress path. The electromagnetic sensor has no wire bonds or semiconductor junctions to fatigue. Shielded cable with overbraid for EMI protection from nearby 440V motor cables. Custom mounting bracket with wire-rope vibration isolators reducing transmitted vibration by 60%.
Installation Location: Tank bottom penetration with isolation valve, transmitter mounted on vibration-isolated bracket 0.5m from penetration. Impulse line sloped continuously upward to transmitter to prevent sediment accumulation.
Result: Transmitter failure rate reduced from 2 per year to zero over 5 years across all 12 installations. The hermetic housing eliminated moisture-related failures entirely. Ballast system now operates in full automatic mode for 100% of voyages—manual intervention eliminated. Loading delays from ballast instrument failure reduced to zero. The vessel operator has since standardized on LVDT pressure transmitters for its entire fleet of 24 vessels, with a cumulative 280 transmitter-years of service and zero failures.
| Characteristic | LVDT Inductive | Bonded Strain Gauge |
|---|---|---|
| Friction / hysteresis | None (core floats in coil bore) | Low but present (adhesive creep, gauge fatigue) |
| Cyclic life | Infinite (no contacting parts) | 10⁶-10⁷ cycles to failure (adhesive fatigue limit) |
| Radiation tolerance | Excellent (copper + iron; minimal degradation) | Limited (adhesive embrittlement, semiconductor degradation) |
| Shock resistance | >100g (mechanical stops limit core travel) | 50-100g (adhesive bond may fracture) |
| Resolution | Infinite (analog electromagnetic principle) | Finite (limited by bridge noise floor) |
| Excitation | AC (1-10 kHz); adds signal conditioning complexity | DC (5-10V); simpler signal conditioning |
| Size / weight | Larger and heavier | Compact and lightweight |
| Cost | 2-3× higher | Lower |
| Temperature range | -50°C to +200°C (continuous); +300°C (with cooling) | -40°C to +125°C (standard); +175°C (special) |
LVDT excitation frequency is the AC carrier signal applied to the primary coil, typically 1-10 kHz for industrial pressure transmitters. The frequency choice involves trade-offs: (1) Higher frequencies (>5 kHz) enable faster dynamic response—the demodulator can track pressure changes up to approximately 1/5 of the carrier frequency (e.g., 10 kHz carrier → 2 kHz measurement bandwidth). This is important for dynamic pressure measurement. (2) Lower frequencies (1-3 kHz) reduce sensitivity to cable capacitance, enabling longer cable runs without signal degradation. (3) The excitation frequency must avoid interference with local EMI sources—for example, a 2.5 kHz excitation near a variable frequency drive operating at 2-3 kHz switching frequency will experience beat-frequency interference. Some transmitters allow the excitation frequency to be adjusted to avoid such conflicts. (4) The excitation frequency appears in the output signal as residual carrier ripple, which must be filtered—higher frequencies are easier to filter without introducing phase lag in the measurement.
Modern LVDT-based transmitters incorporate continuous coil health monitoring by measuring the primary coil current draw and the secondary coil voltage balance. Diagnostics include: (1) Primary open-circuit: detected by zero current draw—triggers immediate fault alarm. (2) Primary shorted turn: detected by increased current draw compared to the factory-characterized baseline—triggers maintenance alert. (3) Secondary open-circuit: detected by zero differential voltage—triggers immediate fault alarm. (4) Secondary imbalance (one coil partially shorted): detected by a change in the null voltage (the residual voltage at the core's null position)—the factory-calibrated null voltage is stored in memory and compared periodically; a drift >50% triggers maintenance alert. These diagnostics enable predictive maintenance: coil degradation is detected weeks to months before catastrophic failure, allowing replacement during scheduled shutdowns rather than emergency repairs. For safety applications (SIL 2), the coil diagnostics provide the diagnostic coverage needed to achieve the required safe failure fraction.
Company Details
Business Type:
Manufacturer,Distributor/Wholesaler,Exporter
Year Established:
Establishe
Total Annual:
5 million-10 million
Employee Number:
500~800
Ecer Certification：
Verified Supplier
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