FAQ

When selecting a Linear Variable Differential Transformer (LVDT) for your application, one of the most important distinctions to understand is whether the LVDT is amplified or unamplified. This classification refers to how the sensor's electrical signal is processed and output.

Unamplified LVDTs (AC LVDTs)

Unamplified LVDTs are also known as AC LVDTs. These sensors require an external signal conditioner to operate properly. They typically produce a low-level differential AC voltage that varies with the position of the core.

Key Characteristics:

• Low-Level AC Output: Outputs a differential AC voltage (typically millivolts).
• Requires External Signal Conditioner: Needs a separate device to provide excitation voltage and to convert the raw output signal into a usable format.
• Smaller Casing and Can be Smaller Diameter: Better for small spaces
• Better for Harsh Environments: AC LVDTs are simple and robust, making them more tolerant of extreme temperatures, vibrations, and shock.

Best For:

• Industrial R&D
• Laboratory testing
• Environments requiring high reliability under tough conditions

Amplified LVDTs (DC LVDTs)

Amplified LVDTs, or DC LVDTs, have internal electronics that handle signal processing within the sensor body. This means they output a standardized signal such as ±10 VDC, 0–10 VDC, or 4–20 mA directly.

Key Characteristics:

• Built-In Signal Conditioning: Contains onboard electronics for easier integration.
• DC Output: Directly provides a high-level output signal compatible with most PLCs and control systems.
• Simplified Wiring: Fewer components to install and maintain.
• More Sensitive to Environmental Factors: Internal electronics can be affected by high temperatures, shock and vibration.

Best For:

• Factory automation and control
• Applications with limited space for external electronics
• Systems requiring quick, plug-and-play sensor integration

Need Help Choosing the Right LVDT for Your Application?
Our experienced application engineers are here to help you select the right sensor for your needs. Contact us today to get started.

Proper installation is essential for accurate and reliable temperature readings in industrial applications. HGSI offers a variety of thermocouple mounting solutions to fit different environments, materials, and operational needs. Here's a breakdown of the most common options and where each one excels:

1. Direct Weld Compression Fitting

Overview:
A compression fitting is welded directly onto the process pipe, duct, or surface.

Advantages:

• Clean and compact installation – ideal where space is limited.
• Permanent solution – provides a secure and stable mounting.

Best For:

• Industrial machinery or piping where access is limited.
• Long-term, high-vibration environments requiring robust mounting.

2. Weld Bung & Separate Compression Fitting

Overview:
A threaded steel bung is welded to the process equipment, allowing the thermocouple to be installed or removed easily using a compression fitting.

Advantages:

• Threaded design allows for easy probe maintenance or replacement.

Best For:

• Applications requiring regular sensor service or calibration checks.

4. Clamp-On or Surface-Mount Fittings

Overview:
These fittings use mechanical fasteners or magnets to attach the thermocouple directly to the measurement surface—no welding required.

Advantages:

• Non-permanent – ideal for testing, diagnostics, or systems that can't be modified.
• Quick installation – no special tools or downtime needed.
• Great for R&D and field service work.

Considerations:

• Less robust than welded options in high-vibration environments.

Best For:

• Research and development.
• Temporary monitoring in manufacturing lines or rotating equipment.

Need Help Selecting the Right Mounting Option?
HGSI’s application engineers are here to help. Whether you're retrofitting an existing system or building a new process, we can recommend or customize a solution to meet your temperature sensing requirements.

Contact Us Today

Both thermocouples and RTDs are temperature sensors used in industrial, commercial, and scientific applications—but they operate on different principles and have distinct characteristics that make them better suited to specific use cases.

1. Operating Principle

• Thermocouples generate a voltage based on the Seebeck effect—when two dissimilar metals are joined and exposed to different temperatures, a small voltage is produced that correlates to the temperature difference.
• RTDs operate based on the principle that a metal's electrical resistance changes predictably with temperature. Most RTDs use platinum wire for precise, repeatable resistance changes.

2. Accuracy and Stability

• RTDs are more accurate and stable over time, especially in the 0°C to 500°C range.
• Thermocouples are less accurate and may drift over time, but can still deliver consistent results in demanding conditions.

3. Temperature Range

• Thermocouples: Can measure extreme temperatures—typically -200°C to 1700°C, depending on the type.
• RTDs: Generally used in the -200°C to 600°C range, with the most accurate results below 500°C.

4. Response Time

• Thermocouples generally have a faster response time, especially when designed with fine-wire or exposed tips.
• RTDs are slightly slower, due to their construction and thermal mass.

5. Durability and Environment

• Thermocouples are more rugged and better suited for high-vibration, high-temperature, or chemically aggressive environments.
• RTDs are more fragile in comparison and typically used in controlled, clean, or lower-vibration environments.

6. Cost and Complexity

• Thermocouples are generally less expensive, especially in basic configurations.
• RTDs are generally more costly but offer better accuracy and long-term stability.

Typical Applications

Which Should You Choose?

Choose a Thermocouple if you need:

• High temperature range
• Fast response
• Rugged design for harsh environments
• Budget-friendly solutions

Choose an RTD if you need:

• High accuracy
• Excellent repeatability and stability
• Long-term measurement in clean, controlled environments

Need help selecting the right temperature sensor for your application?

Contact us now! We offer both thermocouples and RTDs, plus custom designs tailored to your needs.

An LVDT Signal Conditioner is an electronic device that converts the AC voltage signal from a Linear Variable Differential Transformer (LVDT) sensor into a standardized and usable output signal—such as 0–10 VDC, ±10 VDC, or 4–20 mA. It also provides the excitation voltage required to operate the LVDT.

Why Is a Signal Conditioner Necessary?

LVDTs are passive devices that rely on an external excitation source—typically a sinusoidal AC voltage. The signal conditioner performs several essential functions to ensure the sensor provides accurate and reliable position feedback:

Key Functions of an LVDT Signal Conditioner:

Provides Excitation Voltage
Supplies the AC voltage (typically 3 Vrms – from 2.5-10 kHz) needed to drive the LVDT coil.

Demodulates the AC Signal
LVDTs generate an AC signal that varies in amplitude with displacement. The signal conditioner converts this into a DC voltage or current signal that can be easily interpreted by PLCs, DAQ systems, and displays.

Amplifies and Filters the Signal
Enhances the LVDT signal and removes electrical noise or interference for stable, precise readings.

Offers Scalable Output Options
Allows users to choose from common output formats (0–10 VDC, ±10 VDC, 4–20 mA) depending on the control or monitoring system in use.

Enables Zero and Span Calibration
Most signal conditioners include adjustments or digital controls to fine-tune the sensor’s zero and full-scale outputs to match your application requirements.

When Should You Use an LVDT Signal Conditioner?

• You’re using an AC-operated LVDT that does not have built-in electronics.
• You need a standardized signal for input into a PLC, display, or DAQ system.
• Your application requires precision calibration of zero and span.
• You need to reduce noise and ensure signal stability over long cable runs.

Built-In vs. External Signal Conditioning

Some DC-operated LVDTs include built-in signal conditioning electronics. For AC-operated models, an external signal conditioner like the SC-200 or S2A is required for full functionality.

Need Help Choosing the Right Signal Conditioner?

Contact us today—our application engineers are ready to help you select the best solution for your LVDT-based system!

LVDTs (Linear Variable Differential Transformers) are precision sensors used to measure linear displacement. While all LVDTs operate using the same basic electromagnetic principle, the mechanical configuration of the moving core varies depending on the application.

Two common types are Spring-Loaded LVDTs and Free Core LVDTs. Here’s how they differ:

Free Core LVDTs

A Free Core LVDT features a separate, unrestrained magnetic core that moves freely within the sensor body. It does not include a built-in spring or shaft assembly—movement of the core must be externally driven.

Key Features:

• Core is loose and moves independently within the bore
• Requires external guidance or mechanical coupling to the target
• A core extension rod is often used to link the free core to the object being measured, especially when the LVDT is mounted in a fixed location
• Offers a compact and flexible design
• Common in automation, hydraulics, and embedded sensor applications

Best For:

• Applications with space constraints or embedded sensor systems
• Setups where the target or host mechanism drives the core motion
• Environments where a core extension rod can transmit motion from a remote or moving part

Spring-Loaded LVDTs

A Spring-Loaded LVDT includes an internal spring mechanism that automatically returns the core to a rest or home position. These typically include a plunger-style shaft and bearing system to ensure straight-line motion and consistent contact.

Key Features:

• Built-in spring provides return force
• Integrated shaft with mechanical stops
• Designed for surface contact or gaging applications
• Typically larger due to mechanical components

Best For:

• Dimensional gaging and surface measurement
• Bench-top or quality control setups
• Non-permanent installations requiring simple setup and repeatable motion

Which One Should You Use?

Still not sure which type is right for your application?
Contact our application engineers for help selecting or customizing the perfect LVDT for your needs.

Thermocouples come in various types, each with specific properties suited to different temperature ranges, environmental conditions, and accuracy requirements. These types—commonly designated as J, K, T, E, N, R, S, and B—are standardized combinations of metals that generate a voltage corresponding to temperature.

Understanding the differences between these types is essential for choosing the right thermocouple for your application.

Common Thermocouple Types

Type J (Iron–Constantan)

• Temperature Range: 0 to 760 °C (32 to 1400 °F)
• Sensitivity: ~50 µV/°C
• Environment: Best for oxidizing, reducing, or inert atmospheres
• Notes: Not recommended for use above 760 °C due to iron oxidation

Type K (Chromel–Alumel)

• Temperature Range: −200 to 1260 °C (−328 to 2300 °F)
• Sensitivity: ~41 µV/°C
• Environment: Excellent in oxidizing or inert atmospheres
• Notes: Most widely used general-purpose thermocouple; good high-temp stability

Type T (Copper–Constantan)

• Temperature Range: −200 to 370 °C (−328 to 700 °F)
• Sensitivity: ~43 µV/°C
• Environment: Ideal for cryogenic and low-temp applications
• Notes: Very stable and accurate at low temperatures

Type E (Chromel–Constantan)

• Temperature Range: −200 to 900 °C (−328 to 1650 °F)
• Sensitivity: ~68 µV/°C (highest among base metal types)
• Environment: Works well in inert and oxidizing environments
• Notes: High sensitivity makes it suitable for low signal applications

Type N (Nicrosil–Nisil)

• Temperature Range: −200 to 1300 °C (−328 to 2372 °F)
• Environment: Excellent resistance to oxidation and drift
• Notes: Good for high-temp applications where long-term stability is important

Types R, S, B (Platinum–Rhodium Types)

• Temperature Range: Up to 1700 °C (3092 °F)
• Environment: High-temperature applications such as furnaces or kilns
• Notes: More expensive; used in lab, aerospace, and high-temp process control

Which Thermocouple Type Should I Choose?

The best thermocouple type depends on your temperature range, environment, and required accuracy.

Need Help Choosing?

HGSI offers custom-built thermocouples in Type J, K, T, and more—optimized for your specific needs. Whether you're monitoring engine components, conducting R&D, or automating an industrial process, we’re here to help you select the right sensor.

Contact us today to speak with our experienced application engineers.

At Harold G. Schaevitz Industries (HGSI), we’re more than just a sensor manufacturer—we’re a trusted engineering partner for industrial, aerospace, energy, and motorsports applications. From rugged environments to precision lab testing, we deliver measurement solutions you can rely on.

Here’s what sets us apart:

1. Custom Sensor Solutions for Unique Applications

Every application has its own challenges—and we specialize in solving them. HGSI offers custom-designed linear position sensors, temperature sensors, and instrumentation tailored to your specific requirements. Whether you need a modified housing, special stroke length, mounting configuration, or unique output signal—we’ve got you covered.

• Custom LVIT, LVDT, thermocouples, and RTDs
• Pressure and temperature sensors for OEM and specialty use
• Designed to meet demanding environmental or dimensional constraints

If you can’t find it off the shelf, we’ll help you design it from the ground up.

2. Expert Support from Application Engineers

Choosing the right sensor can be complex. That’s why our team of experienced application engineers is here to assist you every step of the way—from selection to implementation.

• Quick, knowledgeable technical support
• Real-world engineering experience
• Application-specific recommendations

We’re committed to providing solutions, not just products.

3. Precision Sensors Built for Industrial Demands

Our products are designed to perform in the most demanding environments. Whether it’s high heat, shock, vibration, or corrosive exposure, HGSI sensors are engineered for durability and accuracy.

• LVIT & LVDT sensors for position feedback in automation, fluid power, and energy
• Thermocouples & RTDs built for fast response and rugged reliability
• Signal conditioners & instrumentation to complete your measurement system
   

Why Choose Harold G. Schaevitz Industries?

• Custom engineering capabilities
• Technical support from real engineers
• Built-to-last sensors for harsh environments
• Proven performance across multiple industries
• Wide selection of USA-made products

From concept to installation, we help you measure with confidence.

Have a project in mind? Contact HGSI today and let’s solve your next measurement challenge—together.

When selecting a Linear Variable Differential Transformer (LVDT) for your application, one important consideration is whether to use a hermetically sealed or non-hermetically sealed model. The difference comes down to how the sensor is built—and how well it stands up to environmental challenges.

Hermetically Sealed LVDTs (Welded Body)

These LVDTs are built with stainless steel housings that are welded at the seams to form a completely airtight seal. This design prevents moisture, dust, or chemicals from entering the sensor.

Advantages:

• Superior environmental protection: Ideal for applications where high humidity, pressure, dust, or fluids are present.
• Built to last: Extended lifespan in harsh industrial or outdoor settings.

Typical Applications:

• Aerospace and aviation
• Subsea or underwater systems
• Power generation (nuclear, hydro)
• Chemical processing environments

Considerations:

• Higher upfront cost to purchase
• Preferred for mission-critical or long-term deployments

Non-Hermetically Sealed LVDTs

These sensors are typically sealed with O-rings, gaskets, or epoxy, but they’re not fully airtight. They work well in clean, dry, and controlled environments.

Advantages:

• Cost-effective: Simpler construction means lower cost
• Reliable for general use in standard industrial or lab settings

Typical Applications:

• Laboratory equipment
• Medical devices
• Factory automation in clean areas

Limitations:

• Reduced resistance to contaminants, moisture, and chemicals
• May have a shorter lifespan in harsh or fluctuating environments

Key Takeaway:

• Choose a hermetically sealed LVDT for tough environments where moisture, pressure, or chemicals are a concern.
• Go with a non-hermetically sealed LVDT for budget-friendly performance in clean, low-risk settings.

Need help selecting the right LVDT for your environment? Contact us today—our engineers are ready to help you find the best fit for your application.

It’s a common question—and a common mistake. While copper wire might seem like an easy and affordable option for extending a thermocouple, doing so can lead to inaccurate temperature readings and unreliable measurements.

Why People Think Copper Wire Is OK

Many people assume copper wire is acceptable because:

• It looks like regular wire and is familiar.
   
• There’s a belief that “wire is wire,” and all conductors behave the same.
   
• For short extensions, some think the impact will be negligible.
   
• Thermocouple theory isn’t widely understood—many people don’t realize that accurate voltage readings depend on using specific metals consistently throughout the entire cable run.
   
• In low-accuracy applications, it might even “seem” to work—until it doesn’t.

Why It’s Actually a Problem

Thermocouples rely on the Seebeck effect, which produces a voltage based on the temperature difference between two dissimilar metals. Here’s what goes wrong when you use copper wire:

1. Incorrect Materials
   Copper doesn’t match the thermoelectric properties of thermocouple wires like Chromel, Alumel, or Iron. Splicing copper in creates extra junctions that behave like unintended thermocouples.
    
2. Distorted Readings
   These new junctions generate additional voltage that interferes with the true signal, leading to false temperature readings.
    
3. Temperature Gradient Issues
   Any temperature differences along the copper extension create unintended thermoelectric effects that throw off the sensor’s output.
    
4. Calibration Errors
   Thermocouples are calibrated based on the specific thermoelectric properties of their metal types. Introducing copper into the circuit disrupts this calibration, resulting in unreliable measurements.

The Right Way to Extend Thermocouple Wires

Always use thermocouple extension wire that matches the type of thermocouple you're using (e.g., Type K, J, T, etc.). These wires are made with the same or compatible materials to preserve measurement integrity and ensure accurate signal transmission.

Need help choosing the right extension wire for your application? Contact our team for guidance!

Extending thermocouple wires seems simple—but if it’s not done correctly, you risk compromising the accuracy of your temperature measurements. Follow these best practices to ensure your readings remain precise and reliable.

 1. Use the Correct Type of Extension Wire

Always use thermocouple extension wire that matches the type of thermocouple you're using (e.g., Type K, J, T, etc.). The metals used in the extension wire must match the metals used in the thermocouple to maintain a consistent thermoelectric signal.

• Do NOT use regular copper wire. It creates unintended junctions and introduces voltage errors that will distort your readings.

2. Match Wire Polarity

Thermocouple wires are polarity-sensitive, meaning each lead has a positive and negative side made from different metals. Carefully match the correct wires when making connections—using incorrect polarity will result in incorrect temperature readings.

• Thermocouple wire insulation is usually color-coded to help identify polarity (e.g., in Type K: yellow = positive, red = negative in the U.S. standard).

 3. Keep Connections Clean and Secure

Poor or corroded connections can introduce electrical noise or resistance that affects your measurement.

• Use proper connectors or terminal blocks rated for thermocouple use.
   
• Avoid using solder at junction points—use crimped or screw terminals made from the proper metals instead to maintain a strong and stable connection.
   

 4. Minimize Junctions

Every junction is a potential source of error. Try to limit the number of splices or connections in the thermocouple circuit.
 

 5. Route Away from Electrical Noise

Thermocouple signals are low voltage and can be affected by EMI (electromagnetic interference).

• Avoid running thermocouple wires parallel to power lines, motors, or other noisy electronics.
  
   
• When possible, use shielded extension wire and ground the shield at one end.
   

Summary:

• Use matching thermocouple extension wire
   
• Observe polarity and proper connections
   
• Avoid copper and minimize junctions
   
• Shield and route wires carefully

By following these best practices, you’ll preserve the integrity of your thermocouple system and ensure reliable temperature data.

Need help selecting the right extension wire or connectors for your thermocouple system? Contact us now - our team is here to help!