Products

Features

• Low noise
  
• 1KV bridge isolation
  
• 60Hz noise rejection
  
• Selectable bandwidth

Description

This instrument is used where strain gages are mounted in an electrically noisy environment, such as a 60-Hz magnetic field. The carrier amplifier's demodulator circuit is properly phased only with the carrier signal, which attenuates random noise.

A master oscillator module supplies carrier voltage to seven amplifier modules. Other provisions include a channel-select switch with a null meter, and controls to vary carrier frequency and amplitude.
External sync is also available
for multi-rack operation.

Bridge configuration: Accommodates a three-wire strain gage

Bridge completion: Completion resistors can be external, or mounted to an internal header

Bridge excitation: 1.4-7VRMS at 10-20kHz, with one common source for all modules in rack; frequency and amplitude are front panel adjustable; multiple racks may be synchronized to one master rack

Bridge balance: Front panel trimpots provide both resistive and capacitive balancing adjustments

Operating modes: Switch selects Zero, Null, Operate or DC cal

Gain: Front panel switch selectable gains of 100, 200, 500, 1000, 2000 with lockable gain vernier

Isolation: 1KVRMS for externally connected bridge elements and calibration resistor

Frequency response: Four-pole active filter; five position switch selects 30Hz, 100Hz, 300Hz, 1kHz, or 5kHz

Carrier filter: Six-pole active filter; 120dB attenuation at carrier frequency; 105dB attenuation at 2x carrier frequency

Output noise: Less than one microstrain, DC to 5kHz

Power: Regulated ±15VDC at 1A, from external supply; Encore Model 821 rack mounted supply or equivalent