A-308 Signal Conditioner/interface for LVDT sensor
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A-308 True-Ratiometric DIN rail LVDT Signal Conditioner

A. A. Lab System's A-308 is a High Accuracy, True ratiometric, DIN rail mounted signal conditioner designed for any LVDT/RVDT application where an analog DC voltage output or 4-20mA current output is required.

DIN rail LVDT 5/6 'wires signal Conditioner

This unit can be used ONLY with 5 or 6 wire sensors. The reading of this signal conditioner is true ratiometric. It calculates: (Va-Vb)/(Va+Vb) and the result is multiplied by the gain. The mechanical zero can be matched to the electrical zero by adjusting the OFFSET trimpot .

The True Ratiometric Din rail mounted LVDT Signal Conditioner is a stand-alone unit. It is powered from +9 to +26V DC (automatic - continuous). The LVDT transducer is connected to it via detachable screw terminals. The unit will outputs a voltage which is highly linear (better than 0.05%) to the displacement (limited by LVDT sensor manufacturer's specifications) or a 4-20mA current loop signal with the same linearity. The unit is mounted in a standard DIN rail case (22.5mm width).

The LVDT conditioner module is designed around high accuracy ASIC that produces a low distortion Sine-wave excitation for driving the LVDT sensor.

The excitation driver can drive sensors with low excitation impedance as most aerospace LVDT sensors. The excitation can supply up to 250 mA to drive the LVDT sensor, allowing enoug current to drive low-impedance sensors as wel as few sensor in parallel (to reduce interference).
This ASIC also demodulates the signal from the LVDT sensor and convert it to a high accuracy, low noise DC coupled signal, ready to interface with the highest accuracy A/D converters and measurement units. All sensitive components are thermally coupled on the silicon chip level, making the LVDT conditioner almost insensitive to temperature variations.

The LVDT signal conditioner board is also insensitive to Excitation level change and Excitation loading due to a State-of the-art true ratiometric measurement technology. Only the ratio between the secondary outputs is measured at real time - independent of the excitation level.

The A-308 boards can operate with almost any type of 5/6 wires LVDT or RVDT sensor available when writing those lines. It's wide dynamic range (with wide range GAIN and DC Offset controls) make it suitable for a wide range of LVDT/RVDT sensors sensitivity. The adjustment of these controls is very easy and can be done by an inexperienced user using a small screwdriver.

All setups are easy for a non-trained user. Most common excitation frequencies can be set by user (13 settings) with fine tuning adjustment to match your sensor's frequency. 4 Low pass filters limit the output noise and allow you to control the dynamic response of the sensor (50Hz, 100Hz, 250Hz, 500Hz).

The A-308 5/6 wires DIN rail mounted LVDT Signal conditioner may also operate with very long LVDT wires. No need for complicated Lead/Lag compensation networks. Since the excitation can drive very high current, few sensors can be hooked to the same excitation signal, reducing interferences between them. The outputs can be read on different signal conditioners (from the same model) without any need to synchronize between them.

Precision Differential Gaging - Each unit features an analog input summed or subtracted from the modules reading for configuration of difference or addition of measurements (Thickness measurements etc.)

More than 1 module can be configured together for synchronous operation of multi-LVDT sensors with the same excitation frequency and phase (Master-Slave configuration).

Polarity LED indicator on front panel for easy center (Zero) setup.

What is "True Ratiometric" measurement?
The LVDT transducer contains a primary winding (input) where a sine wave excitation is connected to and 2 secondary output windings.
If our conditioner board is measuring only the output voltage levels, Va and Vb, and calculate the ratio between them: (Va-Vb)/(Va*Vb) X Gain, then we call it a "True Ratiometric" conditioner because we measure the ratio of the outputs. The True ratiometric signal conditioners can work with very long cable llengths and the reading is independent of the excitation level.





DIN rail mounted LVDT


LVDT 5 wire+buffer

LVDT 6 wires

The A-308 is a High Accuracy, Low cost signal conditioner, for use with most commercial LVDT sensors for accurate distance/position measurement. It’s small size and high accuracy makes it an ideal solution for many applications.

point   Small size.
point   Excitation output: Up to 26Vrms @ 250mA, continuously variable.
point   Can be easily configured for 5,6 wire LVDT/RVDT sensors.
point   Adjustable Gain, Offset, Excitation level, Excitation frequency, Bandwidth.
point   13 user defined excitation frequencies with fine tuning adjustment. Non-Standard frequencies may be also configured at no charge.
point   4 fixed output Low-Pass filters: 50 Hz, 100Hz, 250Hz, 500Hz.
point   High linearity: 0.05%
point   Can be used as Master or Slave unit (for multiple sensor operation using the same excitation frequency and phase, to avoid interference)

point   Low drift: <50ppm/°C of F.S.
point   High frequency response: 50,100,250,500Hz. Standard, up to 20 kHz Optional.
point   Operates with remote sensor: up to 100m.
point   True ratiometric measurement.
point   DC output proportional to position.
point   Single supply operation voltage - +9V to +26V
point   Does not require any compensation networks fo rlong cables.

point   Built-in controls of frequency, filter, offset, gain, excitation.
point   Precision Differential Gaging - Analog "math" input is added or subtracted from current module output voltage (for connection of 2 modules with 2 sensors together).


Bandwidth: 50,100,250,500Hz.
Linearity better than 0.05% of FS
Gain Drift: 20 ppm/°C of FS max.
Offset Drift: 10 ppm/°C of FS max.
Output: Unipolar or Bipolar
LVDT sensor type: Any sensor with 5/6 wires
Supply Voltage: +9V to +26V DC
Output Voltage: ± 10V, 4-20mA
Primary to Secondary phase shift Insensitive
Transducer null voltage Insensitive
Transducer cable length: Up to 100 m
Output cable length: Up to 200 m
Excitation range: 3 - 26 V RMS, Differential
Excitation T.C. 100 ppm/°C max
Excitation Voltage Rejection 100 ppm/dB
Output Current 250 mA peak
Short Circuit Current 300 mA
Frequency range 930Hz. to 10 KHz. 13 Fixed
20Hz. to 20 KHz. preset by factory
Excitation Frequency T.C. 200 ppm/°C
THD - 50 dB
Voltage range +9V to +26V DC
Current (@ no load) 220 mA
Temperature range: -30°C - +60°C

Typical Applications:

5-6 wires
Connection of 5/6 wire LVDT sensors

Differential Gaging
+/-10V or 4-20mA output. Differential measurements

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A.A. Lab-Systems
Head Office: 33 Hayetzira St., Ramat-Gan 52521, ISRAEL.Tel: 972-3-5756327, Fax: 972-3-5756326
USA office: 9 Blossom drive, Kennett Square, PA19348.  Tel: (302)478-2881 Fax: (610)444-5544

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