LVDT Unamplified
The Unamplified LVDT These are inductive transducers in which the sensing element operates without integrated conditioning electronics. Excitation, demodulation, and signal conversion are performed by a external electronics, This allows the sensor body to remain compact and the electronics to be separated from the point of measurement.
Schreiber Messtechnik manufactures different families of Half-bridge LVDT with external electronics, From miniature sensors and precision probes to long-travel transducers, this configuration is particularly useful when space is limited, environmental conditions are demanding, or centralized conditioning electronics are desired.
Quick selection based on the application:
- Miniature and small space: SM20, SM205, SM21 and SM22 families.
- Precision probe: SM22 and SM224 series.
- Threaded mounting: SM24 series.
- Long journeys: SM26 series, with travels of up to 200 mm depending on the version.
- Conversion to 4-20 mA, 0-10 V or ±10 V: use a compatible LVDT conditioning electronics.
What does it mean for an LVDT to be unamplified?
In an unamplified LVDT, the transducer itself contains the inductive measuring system, but It does not incorporate the electronics that transforms its signal into a standard industrial output..
Therefore, the complete system is divided into two elements:
LVDT → external conditioner → analog signal → PLC / data acquisition
This architecture is different from a amplified LVDT, where the electronics are incorporated into the sensor itself and can directly provide an output such as 4-20 mA or 0-10 V.
Why use an LVDT with external electronics?
Separating the sensor from the electronics can offer several advantages depending on the application:
- Smaller sensor size: It allows the development of miniature bodies for installations with limited space.
- Electronics located far from the point of measurement: Useful when it is important to keep electronic components away from areas with temperature, vibration or other demanding conditions.
- Signal flexibility: The same sensor concept can be combined with different conditioners depending on the required output.
- Maintenance: The sensor and electronics can be analyzed or replaced as separate elements.
- OEM Integration: It allows incorporating the measuring element into machinery or equipment using its own or specific electronics.
Actual environmental performance always depends on the selected reference; the absence of integrated electronics does not in itself make the sensor immune to temperature, vibrations or interference.
LVDT Schreiber half-bridge
Schreiber inductive transducers use the half-bridge principle. The displacement of a ferromagnetic core modifies the inductance of the coils, and the external electronics convert that variation into a signal proportional to the position.
This architecture requires that the the conditioner is electrically compatible with the transducer. It should not be selected solely because it has a 4-20 mA or 0-10 V output.
Parameters such as excitation, sensitivity, electrical configuration, and sensor characteristics must be checked.
Check out our category of Schreiber LVDT conditioners and converters for the associated electronics.
Schreiber families with external electronics
| Family | Format | Route | Feature |
|---|---|---|---|
| SM20 | Ø10 mm | Up to 8 mm | Compact design |
| SM205 | 15 × 15 mm | Up to 4 mm | Miniature design |
| SM21 / SM210 variants | Ø10 mm | Up to 20 mm | Compact sensor; versions with cable or connector depending on the reference |
| SM22 / SM224 | Ø8 / Ø10 mm | Up to 20 mm | Probes and versions for precision measurement |
| SM24 | M12 × 1 threaded mount | Up to 15 mm | Mechanical integration by means of thread |
| SM26 | Ø12 mm | Up to 200 mm | Long travel distances; also available as a probe depending on the version |
Dimensions, travel, accuracy, temperature, protection and connections depend on each reference and should be checked in its technical data sheet.
How to select an LVDT without amplification
In this category, the selection should focus especially on the parameters that affect the sensor and its compatibility with external electronics:
- Measurement range.
- Available diameters and lengths.
- Free core, guided stem or return probe.
- Connection type: cable or connector as per reference.
- Operating temperature.
- Required level of protection.
- Sensitivity and electrical characteristics.
- Conditioner to be used.
For a general selection of technologies, you can consult the main category of LVDT sensors.
Cabling, shielding and interference
An unamplified LVDT transmits a low-level inductive signal between the sensor and the conditioner. Therefore, the electrical installation is part of the measurement system.
The recommendations of each manufacturer regarding cable type and length, shielding, grounding, separation from power cables, and conditioner location.
The absence of electronics within the sensor can offer advantages under certain environmental conditions, but It does not imply total immunity against electromagnetic interference..
Frequently Asked Questions about Unamplified LVDT
Does an unamplified LVDT directly deliver 4-20 mA?
No. The transducer needs compatible external electronics to excite the sensor, condition its signal, and generate, if required, an industrial output such as 4-20 mA, 0-10 V, or ±10 V.
Can it connect directly to a PLC?
Typically not to a standard analog input. The LVDT is first connected to a compatible signal conditioner, and the signal conditioner's output is then connected to the PLC.
What is the difference between an amplified and an unamplified LVDT?
The main difference is the location of the electronics. The non-amplified model uses an external signal conditioner; the amplified model integrates the conditioning electronics into the sensor or assembly itself.
Do all conditioners work for any LVDT?
No. The electronics must be compatible with the electrical architecture, excitation, sensitivity, and characteristics of the transducer.
What conditioner is used with Schreiber LVDTs?
Schreiber offers specific electronics for its inductive transducers, including the SM12 family and other modules with different output signals. You can view them at Schreiber LVDT conditioners and converters.
What data does GUEMISA need to select an unamplified LVDT?
Travel distance, available dimensions, mounting type, environmental conditions, and air conditioner reference (if one already exists). For replacing an old sensor, photographs, reference number, and technical data sheet are also helpful.
Selection and replacement of passive LVDTs
GUEMISA can help select a Unamplified LVDT Schreiber for new installations or to study the replacement of an existing transducer taking into account travel, dimensions, mounting and electrical compatibility.
If you already have a conditioner, it is important to indicate your brand, model and electrical specifications to check compatibility with the new sensor.
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