Example Of Research Paper On Lab Assignment#4: Transducer Research II.
Potentiometers are measurement sensors that use a variable resistor to convert a displacement or angle moved through into a voltage/resistance. Potentiometers operate by moving a contact along a variable resistor thus producing a voltage that is proportional to the position. LVDTs (Linear Variable Differential Transformers) comprise a pair of small transformers sharing a magnetic core. Movement of the core causes the output of one transformer to increase and the other to decrease. The current imbalance achieved through this movement is a measure of the core’s position, and optimum linearity occurs at the midpoint where the two transformers are almost balanced.
The aim of this report is to discuss known facts and applications of LVDTs and potentiometers. For the sake of uniformity, two models of each device from the same vendor will be discussed i.e. Spring Loaded and Separate Core LVDT models manufactured by the Macro Sensors Company, and linear potentiometer models by Celesco Transducer Products, Inc that is owned by Measurement Specialties Company.
Linear Variable Differential Transformers (LVDTs):
General Purpose Spring Loaded LVDTs (GHSD/GHSDR 750 Series):
The general purpose Spring Loaded 19 mm diameter GHSD/GHSDR 750 Series LVDTs by Macro Sensors are fabricated using stainless steel, and hermetically sealed making them rugged enough for general industrial applications. The sealing is done to protect the coil turns from hostile environments in compliance standard IP-68 of the IEC while sealed axial and radial connectors are used for electrical termination in GHSD and GHSDR respectively. Radial connectors create a bore that allows air to purge the sensors bearings and eject potential contaminants. The second benefit of the rotary connector is a shorter length of installation compared to GHSD units in the same range using axial connectors. The unit is supplied along with a mating connector plug.
The sensor itself comprises a spring loaded shaft that runs in a precision sleeve bearing and connects the LVDT core. The precision sleeve bearing allows for repeatability measurements to an accuracy of 0.6 μm (0.000025 inches) or better. The probe shaft is extended fully by a spring that exerts a 6 to 20 ounce nominal force depending on the total range. The supplied contact tip is a standard AGD number 9 tip made from tool steel hardened with black oxide. The tip is therefore fully interchangeable with other AGD standard tips.
The LVDTs have built-in electronics that allow position sensors to operate from DC input and produce precalibrated DC output. This output is designed to operate in alignment with various digital indicators, computer data processors, A/D converters, PLCs and QC data collection systems.
Individual models in this series are available in the ranges ±0.020 inches to ±2.00 inches (±0.51 mm to ±50.0 mm) with a maximum linearity error of ±0.25% the full range output. Linearity errors are determined using a statistical straight line of best fit deduced using the method of least squares. The LVDTs have a 1/2-20 UNF-2A mounting thread on the front of the housing that allows users to install the device in a mating threaded component or using the two hex nuts on the sensor. The result is a ready to use sensor package for longer range gaging operations and position measurements. The Table 1 below shows the general specifications of the GHSD/GHSDR 750 LVDTs. Each model in the series has its specifications depending on its range.
Applications of GHSD/GHSDR 750 Series LVDTs:
Some of the specific application areas of the GHSD/GHSDR 750 Series LVDTs include electronic dial indicators, gaging fabricated metal products, industrial gaging systems, large shaft TIR measurements and for use in material testing apparatus.
General Purpose Separate Core LVDTs (DC 750/SE 750 Series):
The Separate Core General Purpose DC 750/SE 750 Series LVDTs have a diameter of 19 mm (3/4 inch) and run on DC. These LVDTs are designed for general purpose industrial applications and have inbuilt electronics that help them provide the same features as LVDTs that run on AC. Such features include dynamic response and frictionless operation with the additional simplicity and convenience provided by DC input and precalibrated DC output. LVDTs in the DC 750/SE 750 Series are designed to work in alignment with computer data processors, Analog to Digital converters, PLCs, QC collection systems and digital indicators.
The series has nine different models thus offering nine different ranges starting from ±1.25 mm to ±250 mm (±0.050 inch to ±10 inches) in the DC 750 Series while the SE 750 Series also has nine standard ranges starting from 2.5 mm to 500mm (0.100 inch to 20.000 inches). The maximum linearity error of the DC 750/SE 750 Series sensors is ±0.25% of the full output range that is determined using a straight line from the best fit derived using the method of least squares. The SE 750 model, however, has a maximum linearity error of ±0.10% the full-scale output range as an available option.
The DC 750/ SE 750 Series sensors deliver a high resolution, highly reliable, contactless operation with impressive repeatability scores, and low levels of hysteresis loss associated with LVDT technology. The exceptional reliability offered by these devices originates from the superior manufacturing and assembling technologies developed and optimized by Macro Sensors in the manufacture of LVDTs over the years. The devices have stainless steel housings that shield them from external magnetic fields induced by AC currents in industrial production environments. The LVDTs in this series are also sealed to meet IEC standard IP-62. There are other options available for the DC 750/ SE 750 Series sensors such as metric threaded cores and Teflon® bore liners. Additionally, DC power supplies, core extension rods, and mounting accessories can be supplied by the manufacturer if needed. The Table 2 below shows the general specifications of the DC 750/ SE 750 Series LVDTs. It should be noted that each specific model in the series has its specifications depending on its range.
Applications of DC 750/ SE 750 Series LVDTs:
The General Purpose Separate Core LVDTs in the DC 750/ SE 750 Series have some specific applications in material testing extensometers, valve position sensing, machine tool positioning, hydraulic cylinder positioning and applications in automatic assembly equipment.
CLP Series Linear Potentiometers:
The CLP linear potentiometer is specifically designed for applications in the automotive racing industry where high precision measurements are desired for speed and safety purposes. The potentiometers in the CLP series are highly reliable and offer unrivaled performance in terms of repeatability, accuracy, ease of mounting and life expectancy. The potentiometers are designed using a combination of conductive plastic materials and precious metal wipers that are individually corrected. These elements provide a measuring system that is cost-effective and one that can operate free from the influence of the external environment. The Table 3 below shows the general, electrical, and environmental specifications of CLP potentiometers.
Applications of the CLP potentiometer:
Designed for the automotive industry but has uses in the general industry too. In Autosport instrumentation, CLP potentiometers are used to measure any kind of linear motion and displacement such as suspension and shock absorber travel, vehicle height at particular speeds, throttle positions, and even spoiler and wing deflections at particular vehicle speeds.
Miniature MLP Potentiometers:
The Miniature MLP series of Potentiometers by Measurement Specialties Inc., deliver high performance and accuracy despite being very small in size. According to the manufacturer, MLP potentiometers are environmentally robust and compliant with the IP-67 standard. They are also known to operate over a broad range of temperatures (-22° to 300°F) and have a high life expectancy of more than 25 million cycles. This makes the MLP miniature potentiometer suitable for a variety of applications in automotive, medical, motion control and general industry automation. The Table 4 below shows the general, electrical, and environmental specifications of MLP miniature potentiometers.
Application areas of MLP potentiometers:
CLP,. CLP Linear Potentiometer. 1st ed. Chatsworth, CA: Celesco Transducer Products, Inc, 2015. Web. 22 Feb. 2015.
Macrosensors.com,. 'DC 750 And SE 750 Series - General Purpose Separate Core DC-Operated LVDT Position Sensors'. N.p., 2015. Web. 22 Feb. 2015.
Macrosensors.com,. 'GHSD/GHSDR 750 Series - General Purpose Spring Loaded DC LVDT Position Sensors'. N.p., 2015. Web. 22 Feb. 2015.
MLP,. Miniature Linear Potentiometer. 1st ed. Chatsworth, CA: Celesco Transducer Products, Inc, 2015. Web. 22 Feb. 2015.