3
1
INTRODUCTION
The S7DC is an in-line d.c. amplifier intended to provide variable excitation and signal
amplification for strain gauge type transducers. It will operate from unregulated single or
dual tracking power supplies and provide up to 10V output (or 4-20mA) with transducer
signals from 10mV to 10V. This allows operation with some high output transducers (DCT,
etc.); for example, to provide 4-20mA outputs with signal inputs up to 10V.
This unit accepts both uni-polar (eg 0 to 4mV) or bi-polar (eg ± 4mV) input signals and can
produce corresponding uni-polar or bi-polar voltage outputs (ie 0 to 10V or ±10V)
sensitivities and gains given in this document refer to both. Current outputs (4 to 20mA)
are uni-polar.
Excitation, coarse gain, fine gain and fine zero controls are provided, with the facility to
connect remotely an internal shunt calibration resistor. Connections are made via screw-
terminals which, with the controls, are all mounted inside an aluminium case, sealed to
IP65 specification.
Note that the voltage output common (0V terminal) with a single (2 wire) supply voltage, is
approximately at the mid supply voltage eg with a 24 volt supply the output common is 12
volts (see section 3.1).
