1.b.5 THE MODEL 3560 VOLTAGE CONDITIONER
This is a general-purpose instrument for conditioning, displaying, and monitoring
the signal received from a DC-to-DC LVDT, potentiometer-type sensor, or other
external two-wire voltage source, either floating (differential) or grounded (sin-
gle-ended). The input signal may also represent output from some other instru-
ment system. Allowable full-scale voltage ranges are ±0.5, ±1.0, ±2.0, ±5.0, ±10.0,
and ±20.0 V-DC (up to ±100 V without damage). A ±12-V excitation is supplied for
sources that require it.
1.b.6 THE MODEL 3570 DC STRAIN GAGE CONDITIONER
This is a general-purpose instrument for input of pressure, force, torque, weight,
and other variables measured by conventional DC-excited strain gage trans-
ducers. It accepts a single input from any conventional 4-arm strain gage bridge,
nominal 120 ohms or higher, with a full-scale range of 0.75, 1.5, or 3.0 mV/V.
(User-supplied bridge-completion circuitry allows input from a 2-wire 1/4-bridge,
3-wire 1/4-bridge, or 1/2-bridge gage configuration.) The user may select a nomi-
nal excitation level of 2, 5, or 10 V-DC. Remote sensing of bridge voltage yields
consistently stable ratiometric measurement, unaffected by possible power-sup-
ply drift.
Simple two-point "zero and span" calibration is provided for the 3570’s input
channel. In addition, a 100-kΩ, 0.1% shunt resistor is supplied. You can use this
resistor—or one of your own—to apply an "equivalent input" for calibration purpos-
es, when the transducer's full-scale mV/V sensitivity is accurately known. The cal-
ibration shunt may be switched in and out for either a positive or negative
up-scale reading via simple commands issued to the RS-232/485 port or by
means of logic-level command signals through the rear Analog Input Connector.
A third calibration technique for the Model 3570 involves application of an "MVV"
command through the RS-232/485 Interface Port when both "mV/V" sensitivity
and corresponding full-scale rating of the transducer are known.
1.b.7 THE MODEL 3578 AC STRAIN GAGE CONDITIONER
This instrument is similar to the Model 3570 DC Strain Gage Conditioner, above,
but is of phase-sensitive carrier-amplifier design. Intended for applications involv-
ing transformer-coupling to the transducer bridge (as with rotary-transformer
torque sensors), it can also be used when high sensitivity is required or where
the electrical environment is especially noisy. Responding only to the modulated
carrier frequency, the 3578 rejects extraneous voltages that can cause errors in
DC systems, particularly when there is a need to "blow up" a portion of the trans-
ducer range.
The Model 3578 accepts input from a 4-arm bridge of nominal 90 ohms or higher,
and a full-scale range of 0.75, 1.50, or 3.00 mV/V. Excitation is fixed at 3 V-AC
(rms) at 3280 Hz. There are user-settable phase and symmetry controls. This
conditioner also offers the same shunt calibration provisions as the 3570, except
that shunt calibration of the AC Strain Gage Conditioner cannot be controlled via
logic-input commands.
1.3
INTRODUCTION
1
1.b GENERAL INSTRUMENT DESCRIPTIONS
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