Application Notes >> Technical Notes

Variable Reluctance Transducer Troubleshooting Guide

This troubleshooting guide describes the most common variable reluctance transducer symptoms, problems and solutions.

• Zero Balance Too High
• Full Scale Output
• Non-Linear
• High Zero Shift

Most performance problems associated with variable reluctance sensors are the result of dirt in the sensor cavity or improper torque on the body bolts. Dirt in the sensor cavity can impede the movement of the sensing diaphragm. The diaphragm moves only about two thousandths of an inch from zero to full scale pressure. Any bit of sand or dirt can keep the diaphragm from sensing the correct pressure. Often the output a contaminated transducer will be linear up to a certain pressure, but then the output stops changing. Simply disassemble the transducer and clean the sensor cavities.

Body bolt torque is also important. The DP15 transducer, for example, requires 115 inch-pounds of torque on each of the four body bolts. Less torque means that there is less clamping force on the diaphragm. This allows the diaphragm to slip out from between the coil housings during full scale pressure excursions. Excessive hysteresis and non-linearity often result. The solution to this problem is easy; simply loosen and then re-torque the bolts.

Problem: Zero Balance Too High

Cause: Warped or Damaged Diaphragm
Solution: Reverse diaphragm. If still out of spec replace diaphragm.

Cause: Contaminated Pressure Cavity
Solution: Clean & Reassemble

Cause: Body Bolts Improperly Torqued
Solution: Loosen & Re-torque Bolts. See Torque Guidelines.

Go To Top

Problem: Full-Scale Output Not in Specification

Cause: Diaphragm Incorrect
Solution: Check Diaphragm Range

Cause: Body Bolts Improperly Torqued
Solution: Loosen & Re-torque Bolts. See Torque Guidelines.

Cause: Obstruction in Pressure Cavity.
Solution: Disassemble & Clean. Clear ports.

Go To Top

Problem: Excessive Non-Linearity

Cause: Over-ranged Diaphragm
Solution: Check Diaphragm Range. Replace if Necessary.

Cause: Obstruction of Diaphragm Movement
Solution: Clean & Reassemble

Cause: Body Bolts Improperly Torqued
Solution: Loosen & Re-torque Bolts. See Torque Guidelines.

Cause: Swollen or Torn O-Rings
Solution: Check for O-Ring Compatibility With Media. Replace.

Go To Top

Problem: Excessive or Erratic Zero Shift Under Line Pressure

Cause: Leak in System
Solution: Recheck all Fittings

Cause: Body Bolts Improperly Torqued
Solution: Loosen & Re-torque Bolts. See Torque Guidelines.

Cause: Missing or Damaged O-Rings
Solution: Replace as Necessary

Cause: Loose Bleed Screw
Solution: Tighten Bleed Screw to 25 In-Lb

Cause: Missing Bleed Screw Gasket
Solution: Replace Gaskets as Required.

Go To Top

TOP