The Ectron Model 778 Wideband Amplifier / Conditioner is an ac-line-powered, all solid-state, high-performance, direct-coupled, wideband differential dc amplifier with transducer conditioning and filtering capabilities. Among its features are excellent linearity, stability, low noise, extremely fast overload recovery, and unique high-frequency common-mode rejection.
Specifically designed to process wideband low-level signals, the Model 778 is ideally suited for use wherever wide bandwidth, high-frequency common-mode rejection, and outstanding overload recovery are required.
Up to ten Model 778 Amplifiers mount in the Model R718 19-inch rack-mount enclosure. Each amplifier has quick-disconnect rear-panel connectors for all inputs, outputs, and power.
BANDWIDTH, FILTER, and COMMON-MODE VOLTAGE
The amplifier bandwidth is dc to 3 MHz with ±300 V common-mode-voltage capability and 80 db of common-mode rejection at 5 MHz. Front-panel-selectable, four-pole-bessel, low-pass filters provide reduced bandwidths of 10 Hz, 100 Hz, 1 kHz, 10 kHz, 100 kHz, and 300 kHz, plus a wideband position.
As the amplifier frequency response is within 3 dB from dc to 3 MHz; at frequencies below 1 MHz, an extremely flat response is provided. For example, from dc to 100 kHz, typical amplitude response is within 0.5% and is within 1% to 1 MHz. This means that for the first time it is possible to make precise data measurements at frequencies from dc to several hundred kilohertz.
GAIN and ZERO
Amplifier gain is continuously variable from 0.3 to 1000 by ten fixed gain steps from 1 to 1000 in a 1-2-5 step sequence plus a gain vernier of 1 to 0.3. Separate front-panel recessed screwdriver adjustments are provided for input and output zero.
Dual independent outputs are standard. One is a low-impedance output for general use, while the second output has a fixed 50 Ω output impedance to match long cables for high-frequency response. Both outputs are controlled by the filter switch. Output connectors are BNC.
Self-calibration is provided by an internally generated calibration voltage that is coordinated with the gain switch. Controls include a front-panel voltage-substitution CAL / OPER switch and a recessed multiturn screwdriver level control.
Transducer conditioning provides constant-voltage excitation, front-panel variable from 0 V to 15 V and a recessed multiturn screwdriver bridge-balance control. Terminals are also provided on a separate plug-in assembly to accommodate completion resistors for one-, two-, and four-arm remote bridges, resistive temperature detectors (RTD’s), or any other bridge-type transducer.
Totally isolated from the amplifier, power, and case; the excitation supply has exceptional overload protection and recovery as does the amplifier.
For personnel safety, the frame of each amplifier/conditioner and the enclosure are connected to power ground and are isolated from all signal inputs and outputs.
The Model R718 enclosure provides mounting for up to ten Model 778 Amplifier / Conditioners in seven inches of vertical panel space in a standard 19-inch rack. Each amplifier is mechanically secured. Power distribution to all amplifiers is provided from a single ac line cord.
- dc to 3 MHz Response
- Differential Input
- 1 MΩ Input Impedance
- <0.1 µs Rise Time
- <0.01% Linearity
- Eight Step, Four-Pole Filter
- 300 V Common Mode Voltage
- 120 dB Common Mode Rejection to 100 kHz
- Plug-in Calibration / Completion Assembly
- 0.1 to 15 V Excitation
- Integral Line Power Supply