Both AC and DC LVDTs (Linear Variable Differential Transformers) are used for precise linear position sensing, but they differ in operation, signal processing, and application requirements. Here’s a breakdown of the key differences:
1. Excitation & Signal Processing
- AC LVDT: Requires an external AC excitation source (typically 1-10 kHz) and signal conditioning to convert the output into a usable DC voltage or current.
- DC LVDT: Contains built-in electronics that provide a DC excitation and output a conditioned analog signal (typically ±10VDC, 0-10VDC or 4-20mA).
2. External Signal Conditioning
- AC LVDT: Needs an external signal conditioner or amplifier to process the raw AC signal.
- DC LVDT: Has integrated signal processing, eliminating the need for an external conditioner.
3. Electrical Noise & EMI Susceptibility
- AC LVDT: Less susceptible to electrical noise and ground loops, making it ideal for harsh environments.
- DC LVDT: More susceptible to noise due to built-in electronics, requiring proper shielding and grounding.
4. Operating Temperature & Environmental Conditions
- AC LVDT: Handles higher temperatures and more extreme conditions because there are no built-in electronics that could be damaged.
- DC LVDT: Limited by the operating temperature range of its internal electronics.
5. Application Suitability
- AC LVDT: Best for high-temperature, rugged, or hazardous environments where signal conditioning can be placed remotely.
- DC LVDT: Ideal for simpler applications where ease of installation and a direct signal output are preferred.
Which One Should You Use?
Choose an AC LVDT when environmental conditions are extreme, long cable runs are needed, or high precision with external signal conditioning is required.
Choose a DC LVDT when you need a self-contained solution that’s easy to install with a direct voltage or current output.