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.