Emerson PR9268 Electric Speed Sensor

Emerson PR9268 Electric Speed Sensor

In process industries such as electricity and petrochemicals, the operational health status of key rotating machinery such as steam turbines, compressors, and fans is directly related to the safety and efficiency of the entire production line. Vibration monitoring is one of the most effective means of evaluating the mechanical condition of these devices. The AMS series PR9268 electric speed sensor under Emerson is designed specifically for harsh turbomachinery applications, used to measure case vibration and provide critical raw data for equipment condition monitoring and protection. This article is based on the PR9268 series sensor specification book, providing a comprehensive analysis of its model selection, technical characteristics, performance parameters, and engineering applications.

Product Overview and Selection Guide

The PR9268 series is an electric speed sensor that converts mechanical vibration into an electrical signal proportional to the vibration speed. Its working principle is based on electromagnetic induction, without the need for external power supply, and it belongs to self generating sensors. This series offers multiple models to adapt to different installation directions and application requirements, and the selection is mainly based on the installation orientation and signal output method of the sensor.

Omnidirectional type (PR9268/01): can be installed in any direction, with a frequency range of 14 to 1000Hz and a sensitivity of 17.5 mV/mm/s. Suitable for situations where installation direction is limited or vibration direction is uncertain.

Vertical type (PR9268/20 and PR9268/60): specifically designed for measuring in the vertical direction. Among them, the installation angle tolerance of the 20 series (without sinking/rising current) is ± 30 °, and the tolerance of the 60 series (with sinking/rising current) is ± 60 °. The latter is suitable for high temperature environments (-20 to+200 ℃).

Horizontal type (PR9268/30 and PR9268/70): specifically designed for measuring in the horizontal direction. The 30 series (without lift/sink current) has a tolerance of ± 10 °, while the 70 series (with lift/sink current) has a tolerance of ± 30 °. The 70 series is also suitable for high temperature conditions.

Detailed explanation of core technical parameters

The technical parameters of the PR9268 series vary depending on different models, and understanding these parameters is the basis for correct selection and application.

2.1 Dynamic Performance

Sensitivity: refers to the output voltage generated per unit vibration velocity. The omnidirectional type (01) is 17.5 mV/mm/s; The vertical/horizontal foundation type (20/30) is 28.5 mV/mm/s; The high-temperature type (60/70) provides multiple outputs, with a sensitivity of 22.0 mV/mm/s at pin 3 and a 100 Ω load, 16.7 mV/mm/s at pin 1 and a 50 Ω load, and 16.7 mV/mm/s at pin 4 and a 20 Ω load.

Frequency range and natural frequency: The working frequency range of the sensor covers the fault frequency of the vast majority of rotating machinery. The basic type (20/30) has the widest frequency range (4 to 1000Hz) with a natural frequency of 4.5Hz; the high-temperature type (60/70) has a natural frequency of 8Hz from 10 to 1000Hz; and the omnidirectional type (01) has a natural frequency of 14Hz from 14 to 1000Hz.

Lateral sensitivity: measures the sensor's ability to suppress non measured axial vibrations. The smaller the value, the stronger the anti-interference ability. The omnidirectional and high-temperature types have excellent performance with a lateral sensitivity of less than 0.1 at 80Hz.

Vibration amplitude and linearity: The mechanical vibration limit can reach up to 3000 μ m (some models can reach 4000 μ m) peak to peak, and the amplitude linearity is less than 2%, ensuring the accuracy of the signal under large vibrations.

Damping coefficient: affects the response characteristics of the sensor near the resonance frequency. The damping coefficient of the basic type (20/30) is about 0.56 at 20 ℃ and about 0.42 at 100 ℃; The high-temperature type (60/70) is about 0.7 at 20 ℃ and about 0.5 at 200 ℃.

2.2 Electrical and Environmental Parameters

Electrical characteristics: Sensors are passive components, and their output signals can be diagnosed by measuring parameters such as coil resistance and inductance. There are differences in DC resistance among different models, such as 1875 Ω± 10% for the basic type and 3270 Ω± 10% for the high-temperature type pin 3.

Working temperature: The omnidirectional type (01) has a working temperature range of -20 to+100 ℃. Both the basic type (20/30) and the high-temperature type (60/70) support wide temperature operation from -20 to+200 ℃, meeting the high-temperature monitoring requirements of turbomachinery.

Protection level: Basic type (20/30) is IP55, suitable for general industrial environments; The omnidirectional type (01) and high-temperature type (60/70) achieve IP65, providing better dust and water spray resistance.

Material and weight: The sensor housing is made of anodized aluminum (basic type) or stainless steel (omnidirectional and high-temperature type) according to different models, which is sturdy and durable. The cable comes standard with stainless steel armor, effectively protecting the signal line. The weight ranges from 280g to 1050g.

Safety certification and suitability for hazardous areas

The PR9268 series sensors have passed multiple international safety certifications, allowing them to be installed in various hazardous areas.

Intrinsic Safety: The basic type (20/30) has obtained the Ex ia IIC T4/T6 Ga rating and is suitable for Zone 0 areas. The high-temperature type (60/70) has achieved Ex ib IIC T3/T4 Gb rating and is suitable for Zone 1 area.

International certification: The product complies with standards such as CE, ATEX, IECEx, CSA, and UKCA, ensuring compliant applications worldwide.

Ordering Information and Accessories

The model code of the sensor includes information such as measurement type, cable length, and terminal type. For example, the number "0" in the model represents a Harting plug, and "1" represents an open cable end. In addition, special versions are also available, such as the OPR version with FEP coated stainless steel armor and the CNSPEC version that requires separate installation of resistance networks. The optional AC100 extension cable can be used for long-distance signal transmission.

Key points of engineering application

Installation direction: Install strictly according to the selected direction to avoid measurement errors caused by installation angle deviation. For horizontal measurement, it is essential to ensure that the sensor is within a tolerance range of ± 10 ° or ± 30 °.

Signal cable: The standard armored cable has good resistance to mechanical damage. In situations with severe electromagnetic interference, it is necessary to ensure that the cable shielding layer is properly grounded.

Intrinsic safety system: When used in hazardous areas, power supply and signal isolation must be achieved through compliant intrinsic safety barriers (such as the MVD DirectConnect series).

Diagnosis: Regularly measuring the DC resistance of the sensor coil can effectively determine the health status of the internal circuit of the sensor and detect potential open or short circuits in a timely manner.