These are highly accurate DC instruments for use with load cells, pressure sensors, and other strain gage transducers employing a 4-arm bridge.
The Model 3170 Strain Gage Conditioner is the basic "Form 1" instrument.
The Model 3270 Strain Gage Conditioner / Indicator is the "Form 2" instrument, providing vivid front-panel digital indication of measured values, scalable in desired engineering units.
The Model 3370 Strain Gage Conditioner / Indicator / Controller is the "Form 3" instrument, and includes HI/LO limit detection with control output. For use of a Model 3370 equipped with internal solid-state relay ("S" Option), see Relay-Controlled Filling Operation.
Advanced circuit design overcomes many of the errors traditionally afflicting the strain gage measurement process, resulting in three high-level, drift-free, noise-free analog outputs. Nearly all mechanical measurement and control requirements are covered by these three simultaneously available outputs.
Other important features include
- remote sensing and regulation of bridge excitation—eliminates errors from temperature effects on cable resistance
- seven-wire calibration circuitry—applies the internal shunt calibration resistor at the transducer terminals, thereby eliminating significant calibration transfer error in long-cable installations
true differential input, with better than 80 dB of common-mode rejection—eliminates errors from common-mode pickup and possible "ground-loop" coupling
- 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.
elimination of both short-term and long-term drift through an advanced solid-state chopper stabilization technique, while preserving the full frequency passband, free of chopper noise; the rated accuracy is obtained without "warm-up" period or periodic "tweaking" of controls
- active low-pass filtering smooths unwanted dynamic signal components arising from vibration, power impulses, etc., that might prevent stable digital conversion or control action
For a special "P" version of the Model 3370 dedicated to the capture and hold of peak torque values. For conditioning inputs from AC-excited strain gage transducers, see the Models 3178, 3278, and 3378.
3000 Series options applying to these instruments include
- Analog Peak Capture (Models 3270 and 3370)
- 4-20 mA Current Output (all models)
- 0-10 VDC Dual Galvanic Isolated Output (Models 3170 and 3270)
- Internal Relays, Electromechanical and Solid-State (Model 3370)
- 12 VDC Battery-Powered Operation (all models)
- Nominal 230 VAC Operation (all models)