Understanding Photoelectric Sensors

Devices

Portable balancer & Vibration analyzer Balanset-1A

Parts

Optical Sensor (Laser Tachometer)

Complete vibration diagnostics and balancing kit from Vibromera, including four vibration sensors with cables, a signal interface module, laser tachometer with magnetic stand, digital scale, USB cable, and a carrying case. The system is designed for field rotor balancing and condition monitoring on industrial equipment.

Devices

Dynamic balancer “Balanset-1A” OEM

Definition: What is a Photoelectric Sensor?

Photoelectric sensor is an optical detection device that uses a light source (LED, laser, or infrared) and photodetector to sense the presence, absence, or position of objects or marks through light transmission, reflection, or interruption. In rotating machinery applications, photoelectric sensors serve as tachometers detecting shaft rotation speed, provide once-per-revolution timing pulses for phase reference in balancing, and enable keyphasor functionality for critical machinery protection systems.

Photoelectric sensors are valued for their non-contact operation, fast response time, immunity to magnetic fields, and ability to detect non-ferrous materials, making them versatile tools for speed measurement and position sensing across all types of rotating equipment.

Operating Modes

1. Through-Beam (Opposed Mode)

Configuration: Light source and receiver in separate housings facing each other
Detection: Object interrupts light beam between emitter and receiver
Range: Long (meters possible)
Reliability: Highest (most immune to dirt, alignment variations)
Application: Blade counting, object detection on conveyors

2. Retroreflective Mode

Configuration: Emitter and receiver in same housing, reflector opposite
Detection: Object interrupts reflected light path
Range: Moderate (several meters)
Convenience: Single-sided installation
Application: Part counting, larger object detection

3. Diffuse Reflective Mode (Most Common for Tachometry)

Configuration: Emitter and receiver in same housing
Detection: Reflection from target surface directly
Range: Short (5-500 mm typically)
Setup: Simple point-and-detect
Application: Reflective tape detection for speed/phase, laser tachometers use this

Applications in Vibration Monitoring

Speed Measurement

Detect reflective tape or shaft features once per revolution
Count pulses to calculate RPM
Continuous speed monitoring
Speed verification during measurements

Phase Reference

Once-per-revolution pulse defines 0° reference
Critical for balancing calculations
Enables phase-locked measurements
Synchronizes order tracking

Keyphasor Function

Permanently installed photoelectric sensor as keyphasor
Detects shaft mark, slot, or feature each revolution
Provides phase reference for proximity probe systems
Essential for turbomachinery monitoring (API 670)

Event Triggering

Trigger data acquisition at specific shaft positions
Trigger stroboscope for stopped-motion viewing
Synchronize measurements to rotation

Specifications

Response Time

Microseconds to milliseconds
Must be fast enough for highest speed measured
Example: 10,000 RPM = 167 Hz → need < 1ms response for clean pulse

Sensing Distance

Minimum and maximum operating distance
Varies by sensor model and target reflectivity
Typical: 50-300 mm for diffuse mode

Light Source

Visible Red: Easy alignment, 630-670 nm
Infrared: Better in bright ambient, 850-950 nm
Laser: Focused beam, longer range, more precise

Installation

Positioning

Perpendicular to reflective surface for best signal
Appropriate distance per specifications
Stable mounting (vibration can affect aim)
Protected from mechanical damage

Target Preparation

Apply reflective tape at suitable location
Clean shaft surface first
Ensure single mark per revolution
Verify mark secure and won’t fall off

Alignment

Aim sensor at reflective mark
Verify stable signal (LED indicator)
Lock position once aligned
Test through rotation to verify reliable detection

Advantages

Non-Contact

No friction or loading
Safe (no contact with rotating parts)
Works at any speed
No wear

Material Independence

Works on ferrous and non-ferrous materials
Works on plastic, composites, wood
Only requires optical contrast

Fast Response

Suitable for high-speed applications
Clean digital pulses
Accurate timing

Limitations

Environmental Sensitivity

Bright ambient light can interfere
Dust, oil mist on optics degrades performance
Requires periodic cleaning
May need protective housing in harsh environments

Alignment Critical

Must maintain aim at target
Vibration or settling can misalign
Requires stable mounting

Target Dependent

Requires reflective mark or object
Reflectivity changes affect performance
Tape can peel off

Photoelectric sensors are versatile optical detection devices essential for non-contact speed measurement and phase reference in vibration analysis and machinery monitoring. Their combination of fast response, material independence, and non-contact operation makes them ideal for tachometer applications, complementing vibration sensors in comprehensive condition monitoring and balancing systems.

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What is a Photoelectric Sensor? Optical Detection Device

Published by admin on October 31, 2025 October 31, 2025