Setting The Amplifier Gain; Oscillator Mode; Oscillator Drive Capability - Measurement Computing LVM-110 Operation Manual

Operation Manual
LVM-110 LVDT/RVDT OEM Signal Conditioner

6.2 Oscillator Mode

The Oscillator mode setting will depend on the number of LVM-110's and LVDT/RVDTs in your system.
For a single LVDT or RVDT system you will be running the LVM-110 in the stand alone (master) mode.
For multi sensor systems, it is best to master and slave the LVM-110 oscillators to prevent beat
frequencies and crosstalk between amplifiers and LVDTs. You will be selecting one LVM-110 to serve as
the master oscillator, and the balance will be set-up in the slave mode.
CAUTION: Attempting to synchronize two LVM-110 set as masters may damage one or both units.
Connecting Pin-1 (Sync) of the barrier strip, from unit to unit, will complete the sync bus circuit. The
power common serves as the return line. Use the table below to configure your oscillator mode:

6.3 Oscillator Drive Capability

To ensure LVDT/RVDT compatibility with the LVM-110 you must know the transducer current draw. The
LVM-110 is designed with a robust sine wave oscillator; it is rated for a maximum drive current of 20mA
RMS with a fixed amplitude of 3 VRMS. To ensure compatibility, you will need to know the LVDT/RVDT
input impedance for the frequency at which you intend to operate it. The transducer input impedance
must be equal to or greater than 150 Ohms, which will result in current draw of 20mA or less. The input
impedance information is available on the datasheets for all MEAS LVDTs and RVDTs.

7 Setting the Amplifier Gain

You will need to calculate the LVDT or RVDT full scale output, using the simple formula below:
LVDT/RVDT sensitivity (in V/V/inch or V/V/degree), at the selected frequency
The full scale of the LVDT in inches (or RVDT in degrees)
As an example, the calculation for a MEAS HR1000 LVDT (±1 inch range; 1 inch full scale), with a sensitivity
of 0.39V/V/inch at 2.5KHZ, would be done as follows:
0.39 x 3 x 1 = 1.17 VRMS full scale output or 1.17 VRMS at ± 1 inch
Using the Gain Selection Table below, select the coarse gain settings (S1 and S2 DIP switches for the two
amplification stages) for the range your full scale output falls into. In our example, you would use the x0.2
HIGH, or the x0.5 LOW settings; either will work, due to range overlap. The gain selections are for a ±10
VDC LVM-110 full scale output.
To calibrate the LVM-110 with your LVDT or RVDT for a ±5 VDC output, double the result of your full scale
output calculation, prior to consulting the gain table. This will result in you selecting half the normal gain,
therefore resulting in half the normal DC output.
Measurement Specialties Inc.
1000 Lucas Way, Hampton, VA 23666, United States
S1-B
OFF
ON MASTER
multiplied with
The excitation voltage, (3 VRMS for the LVM-110)
multiplied with
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Rev. 1 / May 2014
Mode
SLAVE
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