Doucette SLHE1-1/2K NE-1001 | 500 Ohm Linear Position Sensor, In Stock

Description

Key Technical Specifications

Product Introduction

A turbine control system once reported “valve at 62%” for three weeks. The valve was at 40%. The sensor was fine — the coupling had slipped two millimeters on the rod. Nobody had torqued it to spec, and nobody had verified the zero reference after installation. That’s the reality of linear position sensors: the part rarely fails. The installation does.The Doucette SLHE1-1/2K NE-1001 is a linear potentiometric position sensor from Doucette’s SLH series. It tracks straight-line motion and outputs a proportional resistance across a 500 Ω track. Wire it as a voltage divider across a stable reference and the wiper gives you a position-proportional voltage. That’s the whole job. No logic, no address, no protocol.Engineers choose this class of sensor because it’s simple enough to test with a multimeter and cheap enough to keep on the shelf. The 500 Ω value is a deliberate trade — low enough to reject most electrical noise in a control cabinet, high enough not to load the reference supply. I’ve found the mechanical coupling to be the weak link far more often than the resistive track. Mount it rigid, torque the coupling, and verify the endpoints. Do those three things and it’ll outlast the module it feeds.

Quality SOP & Tech Pitfalls

The Lab Report (SOP)Every unit that ships goes through this:

1. Visual and counterfeit check — nameplate photographed; part number, suffix, and housing markings compared against OEM references. Listings describing it as a “controller module” get quarantined first.
2. Continuity check — Fluke 115 across all three terminals. End-to-end resistance measured and recorded.
3. Sweep test — wiper traversed through full travel; resistance checked at 0%, 25%, 50%, 75%, and 100%. Any open, jump, or dead spot fails the unit.
4. Wiper integrity — contact resistance observed for chatter or dropouts during slow traversal.
5. Mechanical check — rod, coupling, and mounting flanges inspected for bends, burrs, and thread damage.
6. Anti-static and mechanical protection — ESD bag, foam cradle, labeled with test date and technician.

Test report and photos ship with the order. Ask for them.The Engineer’s Warning (Pitfalls)Pitfall 1 — Assuming the stroke length matches. The “1” in the model is a stroke code, not a measurement. Two SLH-series units can share a resistance value and have completely different travels. Install the wrong one and the sensor reads full-scale before the valve reaches half travel. The controller won’t fault. It’ll just control wrong.Pitfall 2 — Skipping the endpoint verification. After mounting, drive the mechanism to both mechanical extremes and record the resistance at each. If those two numbers don’t match the OEM drawing, stop. Don’t commission on a “close enough.”Field disaster, anonymized: A maintenance tech replaced a failed position sensor on a control valve during a turnaround. Correct part number, wrong stroke suffix. The loop commissioned clean — no alarms, no faults. Two weeks later the plant ran a load test and the valve slammed to a position the operator never commanded. Root cause: the sensor saturated at 70% travel, so the controller saw “on target” while the valve drove itself into a stop. Cost of the wrong sensor: nothing. Cost of the investigation: three shifts.

Installation & Configuration Guide

Phase 1 — Pre-Installation (⚠️)

1. Place the loop in a safe state. Put the controller in manual or bypass the position feedback input.
2. Depressurize or de-energize the mechanism. Lock out the actuator.
3. Photograph everything — the old sensor’s mounting orientation, coupling position, zero reference mark, and terminal wiring. Minimum four angles.
4. Verify the replacement’s stroke length and resistance against the OEM drawing, not just the model number.

Phase 2 — Removal

1. Label the three terminals — end A, end B, wiper — before loosening anything.
2. Mark the coupling position on the rod with a center punch or permanent marker.
3. Loosen the coupling and mounting hardware. Support the sensor; don’t let it hang by the rod.
4. Remove and bag with the old hardware.

Phase 3 — Installation

1. Set the zero reference before tightening anything. Position the mechanism at its known zero, align the sensor, then torque the mounting hardware. This single step prevents most post-installation faults.
2. Torque the coupling to OEM spec with a torque driver. A slipping coupling is the number one cause of drift.
3. Connect the three leads per your photographs. Confirm end A, end B, and wiper — a swapped pair inverts the signal.
4. Verify the rod moves freely through full travel with no binding or side load.

Phase 4 — Power-On & Testing

1. Energize the reference supply. Measure end-to-end resistance — confirm it matches the nameplate value.
2. Drive the mechanism to both mechanical extremes. Record resistance at each. Compare against the OEM drawing.
3. Traverse mid-stroke points. Confirm the output is monotonic and linear.
4. Verify the controller reads the correct position at each test point.
5. Return the loop to automatic. Log install date, serial, endpoint resistances, and technician.

Compatible Replacement Models

Frequently Asked Questions (FAQ)

Is this a controller or a sensor?
Sensor. Passive resistive position sensor. No processor, no firmware, no communication port. If a listing calls it a “controller module” or “PLC,” that listing is wrong.Can I substitute a different resistance value?
Not without changing the controller’s scaling. A 500 Ω sensor and a 5 kΩ sensor in the same circuit give you completely different voltage outputs. The controller will read position wrong — and it won’t alarm.How do I test it before installing?
Multimeter across the two end terminals — you should read approximately the nameplate value. Then sweep the wiper through full travel and watch for a smooth, monotonic change. Any jump, dead spot, or dropout means reject the unit.What causes most failures on these?
Mechanical, not electrical. Slipped couplings, bent rods, and side loads from misalignment. The resistive track usually outlives the installation.Is it still available new?
SLH-series units are typically build-to-order and this part is obsolete. What’s sold as “new” is usually New Surplus or verified pull. Ask for a nameplate photo and a sweep-test report before paying.Do I need to recalibrate after replacing it?
Yes — always. Drive both mechanical extremes, record the endpoints, and confirm they match the OEM drawing. A sensor installed without endpoint verification is a sensor you don’t trust.Can I hot-swap it?
No. Depressurize or de-energize the mechanism, lock out the actuator, and put the loop in manual first. A moving rod with a partially connected sensor is a damaged sensor and possibly a damaged actuator.