The Model 3570 DC Strain Gage Conditioner is a general-purpose instrument for input of pressure, force, torque, weight, and other variables measured by DC-excited strain gage transducers.  It accepts a single input from any conventional 4-arm strain gage bridge, nominal 120 Ω or higher, with a full-scale range of 0.75, 1.5, or 3.0 mV/V.

Advanced circuit design overcomes many of the errors traditionally afflicting the strain gage measurement process, resulting in rock-solid digital indication and noise-free analog output.

Other important 3570 features include

  • selectable bridge excitation (nominal 2, 5, or 10 VDC
  • remote sensing and regulation of bridge excitation—eliminates errors from temperature effects on cable resistance and yields consistently stable ratiometric measurement, unaffected by possible power-supply drift
  • input impedance in excess of 100 megohms preserves the validity of factory calibration, prevents conversion of common-mode to normal-mode signals, and eliminates remaining errors attributable to cable resistance.  Allowable cable length has virtually no practical limits.
  • selectable active low-pass filtering smoothes unwanted dynamic signal components arising from vibration, power impulses, etc., that might prevent stable digital conversion or control action

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 purposes, when the transducer's full-scale mV/V sensitivity is accurately known.  The calibration shunt may be switched in and out for either a positive or negative up-scale reading via simple mnemonic commands issued to the RS232/RS485 port or by means of logic-level command signals through the rear Analog Input Connector.

A third calibration technique for the 3570 involves application of the special MV/V CALIBRATION (MVV) command through the RS232/RS485 Interface Port when both "mV/V" sensitivity and corresponding full-scale rating of the transducer are known.

The 3570 offers all standard 3500 Series features, including

  • selectable digital smoothing   
  • custom 15-segment linearization   
  • HI/LO limit monitoring with logic I/O   
  • scalable analog output   
  • analog +peak capture   
  • automatic tare offset   
  • digital track and hold   
  • either single-node (RS232) or multinode network (RS485) communications

The instrument can be completely set up and operated either through the front-panel keypad or via simple mnemonic commands received from an external computer or terminal through the RS232/RS485 Interface Port.