SSRL Beamline Electronics

From macrosensors.com

What is an LVDT?
An LVDT (Linear Variable Differential Transformer) is a reliable and accurate sensing device that converts linear position or motion to a proportional electrical output.

The basic LVDT design, as shown in the accompanying drawing, consists of three elements;

1. One primary winding
2. Two identical secondary windings
3. A movable magnetic armature or "core"

The primary winding is excited with an AC supply generating a magnetic field which, when the core is placed in the central or "null" position, induces equal voltages in both of the secondaries. The secondaries are wired series opposed so that their combined output represents the difference in the voltage induced in them, which in this case is zero.

As the core is moved left or right, the difference in induced voltages produces an output that is linearly proportional in magnitude to the displacement of the core. Its phase changes 180º from one side of the null position to the other.

What LDVT's do we use on the SSRL beamlines?

The GHSA 750 Series of rugged LVDT's feature spring extended plungers guided by precision sleeve bearings and in-line electrical connectors. Along with a hermetically sealed coil for protection from hostile environments, they offer good linearity and excellent repeatability.
• Ranges of ±0.05" [±1.25 mm] to ±2.00" [±50.0 mm]
• Repeatability of 0.000025" [0.6 µm] or better
• Rugged design for shop floor gaging
• Mating connector included

How do we wire LVDT's?

The GHSA 750 series LVDT's come with a PT02A-10-6P connector (6 pins). We use an MS31126F 10-6S connector to match on one end of a standard LVDT cable and use a 12 pin Burndy (GOB 12-88 PNE) panel connector that is attached to the bulk head patch panel on the other.

The pin out for the 12 pin Burndy to the LVDT is:

8 Pin Burndy Wire Color LVDT Connector LVDT Function
A brown F primary dot
B white E primary
C blue B sec 1 dot
D red A sec 1
E green C sec 2 dot
F black D sec 2
G unused unused unused
H unused unused unused

How do we scan the LVDT?

We use the Highland M550 8 channel LVDT scanner to supply the primary and rectify the secondary signals. The M550 is a CAMAC module that can be read directly by the computer motion control software.

 

 

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Teresa Troxel 10/30/2003