GB Series LVDT AC Spring Loaded Gauging Probe

The GB Series Spring Loaded AC LVDT Gauging Probe from Harold G Schaevitz Industries (HGSI) is a high-precision linear position sensor engineered for ultra-accurate dimensional measurement in industrial, laboratory, and metrology applications. Designed as a pencil-type gauging probe, the GB Series combines proven AC LVDT technology with a precision spring-loaded mechanism to deliver exceptional repeatability, stability, and long-term reliability.

Built for demanding measurement environments, the GB Series features a stainless steel housing, sealed construction, and robust mechanical design that resists dust, temperature variation, shock, and vibration. These sensors are ideal for applications such as quality control, statistical process control (SPC), materials testing, and precision dimensional gauging.

With stroke lengths ranging from ±0.020 inches to ±0.200 inches, the GB Series provides flexible solutions for both fine-resolution measurement and short-range displacement monitoring.

AC LVDT Measurement Technology

The GB Series operates using Linear Variable Differential Transformer (LVDT) technology, a highly accurate and reliable method of measuring linear displacement. As an AC-operated sensor, the GB Series requires an external signal conditioner to provide excitation and process the output signal.

Typical operating parameters include:

• Input voltage: 3 Vrms nominal

• Input frequency: 5 kHz nominal

When energized, the primary coil generates a magnetic field that induces voltages in two secondary coils. The difference between these signals is proportional to the position of the probe shaft. A compatible signal conditioner converts this differential AC signal into a usable DC output.

Because the sensing element operates using electromagnetic coupling rather than electrical contact, the GB Series provides highly stable and repeatable measurements over long periods of use.

Spring-Loaded Probe Design with Precision Guidance

At the core of the GB Series is a spring-loaded probe shaft guided by a precision linear ball bearing assembly. This design ensures smooth, controlled motion and accurate alignment of the internal core within the sensing element.

A key feature of the GB Series is the non-rotating probe shaft, which minimizes radial play and reduces the effects of side loading. This is critical for maintaining measurement accuracy in applications where even slight mechanical deviations can introduce error.

The spring-loaded design ensures consistent contact between the probe tip and the measured surface, enabling reliable and repeatable measurements across repeated cycles.

Exceptional Measurement Performance

The GB Series is designed for ultra-precise dimensional measurement and offers outstanding performance characteristics:

• Non-linearity: Better than ±0.5% of full scale

• Repeatability: ≤ 0.000006 inches (0.15 µm)

• Sensitivity: Up to 5.3 mV/V per 0.001 inch (depending on stroke length)

This level of repeatability allows the sensor to detect extremely small changes in position, making it ideal for high-precision applications such as metrology and automated inspection.

The high sensitivity ensures strong signal output, improving measurement resolution and signal-to-noise performance when paired with appropriate signal conditioning.

Flexible Stroke Length Options

The GB Series is available in multiple measurement ranges to accommodate a wide variety of applications:

• ±0.020 inches (±0.5 mm)

• ±0.040 inches (±1.0 mm)

• ±0.100 inches (±2.5 mm)

• ±0.200 inches (±5.0 mm)

Each range is optimized to provide the best combination of sensitivity and measurement resolution.

The datasheet also highlights key mechanical characteristics such as:

• Controlled pretravel and overtravel limits

• Consistent spring force of approximately 2.5 ozf (±20%)

These features help protect the sensor from damage and ensure reliable operation within the specified measurement range.

Rugged, Sealed Construction for Industrial Environments

The GB Series is designed to perform reliably in challenging environments. Key construction features include:

• Stainless steel housing for durability

• Fluoroelastomer bellows to protect internal components

• IP65-rated sealing for resistance to dust and moisture

The sensor is also highly resistant to mechanical stress:

• Shock rating: 1000g (11 ms)

• Vibration rating: 20g up to 2 kHz

This rugged construction ensures consistent performance in industrial settings where exposure to vibration, shock, and environmental contaminants is common.

Long Life and Reliability

The GB Series is designed for long-term operation with minimal maintenance. Thanks to its non-contact sensing principle and precision mechanical design, the sensor offers:

• Life expectancy greater than 10 million cycles

Unlike potentiometers or other contact-based sensors, the LVDT does not suffer from electrical wear, ensuring stable output over time and reducing the need for recalibration or replacement.

Electrical Integration and Compatibility

The GB Series includes an integral cable designed for reliable signal transmission:

• 6.5 ft (2 m) foil-shielded cable with drain wire

• Durable polyurethane outer jacket

The sensor is compatible with most conventional differential-input AC LVDT signal conditioners. However, the datasheet specifies that ratiometric signal conditioning is not recommended, ensuring optimal performance when paired with appropriate electronics.

HGSI offers a full range of compatible signal conditioners to support integration into control systems, data acquisition setups, and measurement instrumentation.

Mechanical Configurations

The GB Series is available in multiple body configurations to suit different installation requirements:

• Plain 0.315-inch diameter (GBP-315)

• Plain 0.375-inch diameter (GBP-375)

• Threaded 0.375-inch diameter (GBT-375)

Each configuration allows flexibility in mounting and integration, making the sensor suitable for a wide range of applications and mechanical setups.

Typical Applications

The GB Series is widely used in applications requiring high-precision linear measurement, including:

• Laboratory R&D and materials testing

• Industrial gauging test stands

• Factory automation and inspection systems

• Quality control and SPC measurement processes

• Precision dimensional metrology

Its combination of high repeatability, durability, and flexibility makes it an ideal choice for both manual and automated measurement systems.

Summary

The GB Series LVDT AC Spring Loaded Gauging Probe provides a high-performance solution for ultra-precise linear position measurement. With its non-contact sensing technology, precision-guided probe shaft, and rugged sealed construction, it delivers exceptional repeatability and reliability in demanding environments.

Whether used in laboratory metrology, industrial inspection, or automated testing systems, the GB Series offers accurate, stable, and long-lasting performance. For applications requiring precise dimensional measurement and consistent results, it is a proven and dependable solution.