Excitation Voltage

Full-bridge LVDT sensors require an excitation voltage to feed the strain gage bridge and generate their output signal as a ratio of the input excitation voltage. Thus, you need to establish if your DAQ or PLC can support the sensor’s input voltage or excitation voltage requirements. Simply put, an unstable excitation voltage input leads to an unstable sensor output. In case you you need a LVDT amplifier module for PLC or DAQ and they do not provide a stable input excitation voltage, the amplifier will be the excitation voltage source to ensure the sensor provides a reliable and consistent output signal.

Filtering

Analog sensor signals are susceptible to electrical noise and/or residual ripple voltage, which can distort or skew measurements. Noise needs to be filtered out before you can capture an accurate signal. DAQs and PLCs designed to interface directly with full-bridge sensors will include pass band and other forms of signal conditioning and filtration. In a low noise signal conditioner, electronic filters eliminate some effects on accuracy by removing electrical noise and ripple effect above and below the analog sensor’s signal range, resulting in a low signal to noise ratio.

Amplification

Sensors can output a signal in the nanovolt through millivolt range. When your DAQ or PLC is limited to measuring volts, you will need an strain gage amplifier to convert millivolts to a larger signal. Some PLCs and DAQs come with built-in amplification; others will require an external amplifier. What if your existing DAQ or PLC does not provide built-in amplification, signal conditioning, and a stable power source for sensor excitation? In that case, you will need an amplifier to fill in the shortfalls in your instrumentation.

USB520 Features

• USB 2.0 Communication Link;
• USB Bus-Powered (5V);
• Input/Output Short Circuit Protection;
• Streaming ASCII Output;
• Offered with DLL/Mac Dynamic Library;
• CE Approved Class A (required for Medical and Aerospace applications);
• Industrial metallic enclosure;
• Integrated DIN rail mount;
• Supports, VDC, mA, mV and TTL type input.

Dimensions

Specifications

What is a Linear Variable Differential Transformer?

An LVDT is an electromechanical sensor used to transform mechanical motion into a variable electrical signal (current or voltage) and is used for measurement of displacement. They function as actuators for automatic control systems or as mechanical motion sensors in measurement technologies.

LVDT is an acronym for Linear Variable Differential Transformer. LVDT linear position sensors can measure displacements ranging from few microns to centimeters, but are also capable of measuring positions up to ±1 meter.

In short, a LVDT sensor provides output quantity in voltage or current, related to the displacement or movement being measured. LVDT Transducers are prone to external electromagnetic interference.

A linear displacement transducer requires three to four connection wires for power supply and output signal delivery.

Physically, the LVDT Transducer construction is a hollow metallic cylinder in which a shaft of smaller diameter moves freely back and forth along the cylinder's long axis. The shaft, or pushrod, ends in a magnetically conductive core which must be within the cylinder, or coil assembly, when the device is operating.

In common practice, the pushrod is physically attached to the moveable object whose position is to be determined (the measurand), while the coil assembly is attached to a fixed reference point. Movement of the measurand moves the core within the coil assembly; this motion is measured electrically.