1. Application and measurement type. Common type of pressure measurement include: Absolute, gauge, differential, vacuum, bidirectional, and sealed gage. 2. Pressure range. kPa, Bar,Psi, Mpa 3. Process media. Water, Oil, Gas etc 4. Temperature range and installation environment. -30~80℃ etc. 5. Accuracy. ±0.25%F.S. 6. Output. 4~20mA, mV, 0.5~4.5Vdc etc
How to choose a load cell 1. Consider the load input direction. 2. Consider the object to be weighed: capacity, resolution, shape. 3. Consider the environment the Load Cell will operate in. 4. Consider the desired accuracy, error ratings, and ease of calibration. 5. Select the load cell type for the application.
The base body is made of stainless steel. The resistance structure is produced by photolithography. Thin-film measuring cells stand out due to their excellent resistance to pressure peaks and bursting pressure.
Electronic pressure measurement requires a sensor that records the pressure to be measured and converts it into an electrical signal. Due to the large output signals and the established manufacturing processes, as well as the many years of experience gained, piezoresistive technology has become established in pressure measurement.
Transducers generally convert energy from one form to another, although the energy is typically a signal. They are routinely used in automated systems, which are often controlled by measurements of physical quantities such as force, motion, temperature and pressure. A sensor is a specific type of transducer that senses a physical property of its environment and reports that change, typically in the form of an electrical signal. For example, a pressure sensor detects pressure and reports it to a gauge that displays the pressure.
Potentiometer - a contacting technology used in both linear and rotary sensors. Hall effect - more popular with rotary sensors but can also be used in linear sensors, non-contacting technology. Inductive - non-contacting technology using alternating currents to measure linear position. LVDT - non-contacting linear sensors - linear variable differential transformer RVDT - non-contacting rotary sensors - rotary variable differential transformer Eddy Current - inductive non-contacting measuring method for linear and rotary movements
The pressure measurement system is made up of a sensing element with four strain gauges applied to it. The strain gauges are configured in a Wheatstone bridge, where all 4 resistors (labeled R1 thru R4 in Figure 2) are equal, and change by equal magnitude proportionally, when strain is applied. The greater the force or strain (input), the greater the output. A Wheatstone bridge device requires 4 wires for its connection, positive and negative excitation, and positive and negative sensor output.
The rated capacity is the maximum recommended load for a particular load cell. All load cells have a range of loads where the output signal is proportional to the load; that is the deformation of the strain gauge caused by the load produces an output signal having an approximately linear relationship to the strain. By keeping the rated capacity in this range, the strain gauge produces outputs within the errors printed on the accompanying load cell data sheet.
Higher voltages through the resistive strain gauges (which comprise the Wheatstone bridge) will cause more current to flow and heat the strain gauges. The cell body acts as a heat sink to keep the gauges cool. If the maximum rated excitation voltage is exceeded, the heating will cause signal perturbation or gauge failure. Additionally, in battery operated devices, high excitation voltage (and thus, current) will cause the battery to deplete much faster than with lower excitation voltages through the circuit.
Load cells have a specified load direction, do not apply side forces, bending or torsional movements on load cells. Inappropriate loading applications will risk reducing the life of load cells, plus distortion of correct measurement results.