Pressure Sensor Selection and Installation Guide

I. Common Definitions

◆ Standard Pressure: Pressure expressed relative to atmospheric pressure. Pressure greater than atmospheric pressure is called positive pressure; pressure less than atmospheric pressure is called negative pressure.

◆ Differential Pressure (Pressure Difference): The relative difference between two pressures.

◆ Absolute Pressure (A): Pressure expressed relative to vacuum.

◆ Gauge Pressure (G): Pressure relative to standard pressure. Gauge Pressure = Absolute Pressure - Atmospheric Pressure

◆ Atmospheric Pressure: Pressure exerted by the air column at Earth's surface due to gravity. It varies with altitude, latitude, and weather conditions. 1 standard atmosphere (1 atm) equals the pressure exerted by a 760mm column of mercury.

◆ Vacuum: A pressure state below atmospheric pressure. 1 Torr = 1/760 atm.

II. Product Selection

◆ Pressure Sensor: A sensor that detects pressure and converts it into an electrical signal output proportional to the pressure. Pressure sensors are critical components in pressure detection systems. Their electrical output can display pressure values on indicators or be used for control and alarm purposes.

◆ Pressure Transmitter: A measuring instrument that converts pressure variables into a standardized, transmissible output signal. Its output signal maintains a given continuous functional relationship with the pressure variable (typically linear). Primarily used for measuring and controlling industrial process pressure parameters.

To ensure your selected product meets field requirements, refer to the following during selection:

◆ Pressure Type

Confirm the type of pressure being measured: gauge pressure, absolute pressure, differential pressure, etc.

◆ Measurement Range

Generally, select a sensor/transmitter with a pressure range approximately 1.5 times greater than the required measurement value. Many test systems, particularly in hydraulic measurement and processing applications, involve peak pressures and sustained irregular fluctuations. These instantaneous peaks can damage pressure sensors, while sustained high pressures or values slightly exceeding the sensor/transmitter's rated capacity can shorten sensor lifespan. For instance, the impact force during a loader's lifting cycle poses a severe challenge to sensors. Such applications often require safety overloads exceeding 3 times the rated capacity, though this compromises overall accuracy. Damping devices can be employed to reduce pressure shocks, but they also decrease the sensor's response speed. Therefore, when selecting a sensor/transmitter, thoroughly consider the pressure range, accuracy, and stability to choose the most suitable solution.

◆ Measured Medium

Generally, viscous liquids (e.g., crude oil), coal slurry, mud, and other sediments can clog pressure ports and disrupt sensor operation. In such cases, sensors with isolation diaphragms (i.e., flat diaphragm pressure transmitter) should be used to measure pressure directly against the medium. When solvents contain corrosive substances, isolation diaphragms made from materials compatible with these media must be selected; otherwise, product lifespan will be compromised.

◆ Product Accuracy

Accuracy here primarily refers to: nonlinearity, hysteresis, repeatability, zero and full-scale deviations, and the effects of temperature and other environmental factors. Generally, higher accuracy translates to increased product manufacturing costs and higher sales prices. Therefore, customers should not solely pursue high accuracy when selecting products but should make reasonable choices based on actual measurement requirements.

◆ Temperature Range

Transmitters typically specify two temperature ranges: the normal operating range and the temperature compensation range.

The normal operating range defines the temperature limits within which the product functions without damage. Performance specifications may not be met when operating outside the temperature range.

Temperature Compensation Range: Within this range, the product will reliably achieve its specified performance metrics.

Temperature variations affect: zero drift and full-scale output. Without these parameters, it is difficult to determine whether changes in transmitter output are caused by pressure variations or temperature shifts. Therefore, this should be a key consideration during selection.

◆ Output Signal

Common output signals include: mV, V, mA, frequency output, and digital output.

For equipment with short distances between transmitters and controllers, transmitters with V output are generally economical and effective.

For long-distance transmission or environments with strong electronic interference signals, mA output or frequency output should be used.

In environments with high RFI or EMI levels, besides selecting mA or frequency output, special protection or filters must also be considered to ensure normal product operation.

◆ Supply Voltage

The type of output signal determines the required supply voltage.

Many transmitters feature built-in voltage regulators, enabling them to operate within a wide power supply voltage range (e.g., 12–30 VDC commonly used in automation).

Some transmitters are fixed-configuration devices requiring a stable operating voltage (e.g., 5 VDC commonly used in automotive equipment).

◆ Verify Field Operating Environment

Assess whether the site contains vibration or electromagnetic interference, and provide this information during selection to enable appropriate countermeasures.

III. Installation

◆ Carefully read the product manual and verify all product details before installation.

◆ Install sensors in well-ventilated, dry, non-corrosive, and shaded locations. For outdoor installations, use protective covers to prevent sunlight and rain from affecting normal operation.

◆ Avoid strong impacts or blows during installation.

◆ Connect wiring according to the correct wiring diagram, taking care to protect the sensor's lead wires.

◆ When cleaning the sensor's pressure port and pressure-sensing holes, inject trichloroethylene or alcohol into the pressure-sensing holes, gently shake the sensor, then drain the liquid. Repeat this process multiple times.

◆ Do not insert any hard objects into the pressure-sensing holes to prevent damage to the sensitive core.

For details, please contact Qi Huang: qihuang@utopsensor.com