Encore Electronics

Model 179 Computer-Controlled Charge Amplifier / Integrator




The Model 179 computer-controlled charge amplifier module features variable gain and output scaling and accepts either differential or single-ended inputs. Adjustable parameters include: accelerometer sensitivity, differential or single-ended mode, scaling, filter setting, external calibration and zero mode.

Specifications Channel A

Input Channel A = charge

Accel sensitivity: Any value from 2.0 to 200pC/g
Output scaling: 1mV/g, 10mV/g, 20mV/g, 100mV/g
Gain accuracy: ±1%
Input mode: Differential or single-ended (-IN tied to common)
Maximum input: 50,000pC peak per input (50,000pC differential):
2,800pC peak with sensitivity set to 2.0 –   9.9pC/g
12,500pC peak with sensitivity set to 10  – 49.9pC/g
50,000pC peak with sensitivity set to 50  –  200pC/g
Frequency response: 20kHz at 50,000pC peak input level, increasing to >35kHz at 25,000pC peak input level (or lower)
Calibration: Internal 1015pf ±1% capacitors convert ExtCal voltage signal to charge, which can be applied to amplifier front end
Zero mode: Relays replace charge converter output with short to common


Specifications Channel B

Input channel B = millivolt, with optional 4mA excitation for transducer

Calibration: External ExtCal voltage signal can be applied to front end
Excitation: 4mA constant current can be tied to +S, with -S tied to common
Gain: 1 or 100


Specifications Common

Features common to both output channels

 Filter: Eight-pole Butterworth lowpass at 12Hz, plus OUT, six-pole Butterworth highpass at 5kHz, 15kHz or 25kHz
Filter input signal: Select either charge input or millivolt input
Pre-integration Filter: Three-pole Butterworth lowpass at 250Hz, 500Hz, or 1kHz
Integration Select: Accel, velocity, displacement, or unfiltered (5Hz-12kHz) accel
 RMS/DC Select: Either AC signal or DC representation or RMS value
Limit Detect: Two front-panel LEDs indicate saturation at charge amp, before filters, and at integration stages
Offset: Less than 5mVDC at output
Noise: Less than 3mV RMS, filter in, input disconnected


Rack Mounting

Mechanical: 5.5” x 13.5” board, used with Model 5020-102 rack