Spring Loaded 4-20 mA Loop-Powered
LVDT Position Transmitters

Macro Sensors’ GHSI and GHSIR 750 Series of 3/4 inch (19 mm) diameter, spring-loaded, 4-20 mA loop-powered LVDT position transmitters are designed for a wide range of position monitoring and feedback applications. These rugged hermetically sealed sensors are constructed entirely of stainless steel, and are intended for general industrial use. The coil windings are sealed against hostile environments to IEC standard IP-68 and input/output connections are made through a sealed axial (GHSI) or radial (GHSIR) connector. The radial connector offers two important benefits. First, it results in a through-bore design, which allows for air purging of the sensor's bearings to remove potential contaminants. The second advantage of the radial connector is shorter installed length compared to units of the same range with axial connectors. The mating connector plug is supplied with the unit.

The sensor consists of a spring loaded shaft running in a precision sleeve bearing and connected to the core of an LVDT. The use of a precision sleeve bearing results in measurement repeatability of 0.0001 inches (2.5 μm) or better. The probe shaft is fully extended by a spring exerting a nominal force of 6 to 20 ounces depending upon total range. The contact tip supplied is an AGD standard number 9 made from black oxide hardened tool steel. It is fully interchangeable with other 4-48-threaded AGD contact tips.

Macro Sensors also offers an air-extend/spring-retract version of the radial model. The GHSIR 750-A is designed for a wide range of cycled position monitoring, feedback, and automated dimensional gaging applications where it is necessary or desirable to move the probe out of the way between readings. The shaft is extended by introduction of a low-pressure (10-30 psi), clean, dry air supply, with a regulated flow, through a 1/4 inch barbed fitting on the end of the unit. With the release of pressure, an internal spring returns the probe to its normal position.

GHSI and GHSIR 750 Series transmitters offer the frictionless operation, high resolution, excellent repeatability, and low hysteresis associated with LVDT technology, along with the convenience and simplicity of precalibrated 4-20 mA current loop operation. Units operate either as 2-wire loop-powered or 3-wire sourcing externally powered. The built-in electronics operate over a wide range of loop supply voltages and resistances, and are designed to operate with many PLCs, digital indicators, A/D converters, computer-based data processors, and QC data collection systems.

Available in ranges of 0.100 inch (2.5 mm) to 4.00 inches (100 mm), the linearity error for GHSI and GHSIR 750 Series sensors is ±0.10% of full range output or better using a statistically best-fit straight line derived by the least squares method.

For simplified mounting the GHSI and GHSIR 750 Series have a 1/2-20 UNF-2A thread on the front of the housing, permitting the user to install the LVDT in a mating threaded part or by using the two hex nuts furnished with the sensor. This results in a ready-to-use package for position measurements and longer range gaging applications.