Model 10A78 Single Channel AC Strain Gage Condtioner
is a single-channel conditioner of phase-sensitive carrier-amplifier design (rather than a two-channel, fully DC instrument). Intended for applications involving transformer-coupling to the transducer bridge (as with rotary-transformer torque sensors), this conditioner can also be used in conventional installations when high sensitivity is required or where the electrical environment is especially noisy. Responding only to the modulated carrier frequency, the 10A78 rejects extraneous voltages that can cause errors in DC systems, particularly when there is a need to “blow up” a portion of the transducer range. User-adjustable phase and symmetry controls are provided.
The Model 10A78's data channel is best calibrated by means of a “two-point (deadweight)” or shunt-calibration technique, following an initial “calculated” calibration. The supplied calibration resistor is 59 kOhms, 1%.
The Model 10A78 conditions Transducer Types: Conventional 4-arm strain gage bridges, nominal 350 ohms (or higher) with Input Ranges (Full-Scale): ±0.75, 1.50, or 3.00 mV/V; automatically selected—on an individual channel basis—when the channel is configured.
Since channel zeroing is by digital techniques, no input balance control is provided. The allowable input range, therefore, must include any initial unbalance. Some transducers may have to be externally trimmed to be used with the Model 10A78, if zero unbalance exceeds 20% of full scale.