PC104-73DL1
LVDT/RVDT OUTPUT, PROGRAMMABLE
16 BIT RESOLUTION; WRAP-AROUND SELF TEST
ON-BOARD PROGRAMMABLE EXCITATION SUPPLY (OPTIONAL)
FEATURES:
鈥?16 bit resolution
鈥?Continuous background bit testing and Excitation loss detection
鈥?Transformer isolated
鈥?No adjustments or trimming required
鈥?Part number, S/N, Date code, & Rev. in permanent memory
DESCRIPTION:
This PC104 compliant stackthrough module offers (1) three-wire transformer isolated
鈥淧ROGRAMMABLE鈥?LVDT/RVDT outputs with wrap-around self test and optional excitation supply.
Instead of buying cards that are set for specific outputs, the uniqueness of this design makes it
possible to buy our generic card that can be programmed and reprogrammed in the field for any
excitation and signal voltage between 2.0 and 28 volts. One transformer isolated excitation is supplied
for the A, B output pair. User selects the desired A+B voltage. After this is done, the card will
automatically set the correct B voltage for any programmed A voltage.
Use of a ratiometric design
eliminates errors caused by excitation voltage variations. The outputs are stable with temperature and
switching spikes are not noticeable. To simplify logistics, Part number, S/N, Date code, & Rev. are located in
permanent memory locations.
Automatic background bit testing where the output of each channel is compared against the commanded input
to a testing accuracy of 0.1% FS and each Signal and Excitation is monitored. Any failure triggers a flag. The
testing is totally transparent to the user, requires no external programming, has no effect on the standard
operation of this card and can be enabled or disabled via the bus. The results are available in status registers.
Principal of Operation (LVDT):
Typically the primary is excited by an ac source, causing a magnetic flux to be
generated within the transducer. Voltages are induced in the two secondaries, with the magnitude varying with
the position of the core. Usually, the secondaries are connected in series opposition, causing a net output
voltage of zero when the core is at the electrical center. When the core is displaced in either direction from
center the voltage increases linearly either in phase or out of phase with the excitation depending on the
direction.
Interfacing LVDT to Converter
Two common connection methods are:
1. Primary as reference (Two-wire system)
2. Derived reference (Three/four-wire LVDT)
Two-wire system:
This method of connection converts the widest range of LVDT sensors and. is the most
sensitive to excitation voltage variations, temperature and phase shift effects.
Three/four-wire LVDT:
The LVDT is again excited from the primary side, but the converter reference is the
sum of A + B that has constant amplitude for changing core displacement This system is insensitive to
temperature effects, phase shifts and oscillator instability and solves the identity (A-B)/(A+B)
Apex Signal, A Division of NAI, Inc.
Bohemia, NY 11716 USA
www.naii.com
Code: 0VGU1
Model PC104-73DL1 Specifications
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