Hermetically Sealed 4-20 mA
LVDT Position Sensors

Macro Sensors’ HSI and HSIR 750 Series of 3/4 inch (19 mm) diameter, loop-powered 4-20 mA 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 (HSI) or radial (HSIR) connector. The radial connector offers two important benefits. First, it results in a through-bore design, which permits access to either or both ends of the LVDT’s core for better mechanical support and core guidance, and easier cleanout in dusty or dirty locations. 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.

HSI and HSIR 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 1 inch (25 mm) to 10 inches (250 mm), the linearity error for HSI and HSIR 750 Series sensors is ±0.25% of full range output or better using a statistically best-fit straight line derived by the least squares method. A version with less than or equal to ±0.10% linearity error is also available. HSI/HSIR 750 position transmitters have an open bore at one end into which the LVDT's core enters. Normally, loop current will be 4 mA when the core is first inserted, increasing to 20 mA when the core is at full range within the transmitter's body. For position sensing that requires the opposite directional sense, HSI/HSIR 750 transmitters are available with reversed output slope, which gives 20 mA when the core is first inserted, decreasing to 4 mA as the core moves inward.

Macro Sensors offers several standard options that permit a user to customize HSI/HSIR 750 LVDTs, including Teflon® bore liners and metric threaded cores, as well as smaller diameter and low mass cores. In addition, Macro Sensors can provide a range of mounting accessories and core extension rods.