Signal Conditioner/Amplifier                                              8000  


R.C. Electronics Inc. advances the state of the art in signal conditioning with the Model 8000 Computer Controlled Signal Conditioner and Amplifier. The Model 8000 combines the high precision and proven reliability of manually controlled amplifiers with the speed, convenience and accuracy of operation resulting from computer control.

The 8000 offers the operator many advantages, including the ability to quickly and accurately set gain offset, filter cutoff and excitation voltage from a local or host computer. Settings may be made either individually via the computer keyboard or a complete test setup of all amplifiers may be made in seconds using data stored in the host computer memory.

In addition, all these parameters can be read back from the 8000 by the host computer to display overall status or provide a permanent printed record. The 8000 also has a status output that, upon interrogation, allows the user to record all settings over the Tape or Galvo output in a PCM coded format.
Interfacing to the host computer is provided by an RS-232C or IEEE-488 bus. An optional portable computer can be used to provide local control via a second dedicated RS-232C port.

The Model 8000 consists of a main frame and a plug-in Bridge Completion Module. The main frame provides the isolated power for the excitation supply and a high precision differential DC amplifier. The Bridge Completion Module allows the user to handle all types of resistance transducers including strain gauges, RTDs and potentiometers. Each conditioner is fully guarded and isolated as required to maintain signal integrity. System hardware consists of three major components: Model 8000 Signal Conditioner/Amplifiers, a Master Rack and a Slave Rack.

The Master Rack houses the initial group of eight Model 8000s with a Slave Rack for each additional group of eight. Slave Racks can be accommodated to allow system expansion to as many as 2048 Model 8000 units. The Master Rack contains the master microprocessor which communicates with the host computer, the portable local computer and the microprocessor in other Slave Racks. The master microprocessor speaks to all slaves by a round robin serial link, allowing complete data verification between all groups of 8000s.
Each Model 8000 is controlled directly by the microprocessor in its Master or Slave Rack.

The 8000’s precision differential DC amplifier features multiple feedback techniques to reject common mode signals. Input impedance is greater than 50 megohms. Bandwidth is 500 kHz. The power supply’s triple-shielded power transformer provides maximum isolation for transducer excitation.

Design Features

A versatile plug-in card is provided with the Model 8000 allowing the user to complete two independent bridges via an 8-pole DIP switch. This is an easy means of switching between two bridges of different resistance (e.g. 120 Ohm and 350 Ohm).

In addition to bridge completion, there are provisions on the plug-in card for mounting up to 16 Shunt Calibration resistors. This will support up to ±4 steps of single or double Shunt Calibration. Four resistors are selectable per step of single shunt calibration or two resistors per step of double-shunt calibration.

All transducer input wires (up to 10 conductors plus a shield) are routed through the Bridge Completion card. Included on the card are provisions for the addition of components (resistors and capacitors) for customizing the Model 8000 to suit a wide range of applications. These include but are not limited to the following functions: 1) AC coupling in input signal; 2) Custom voltage dividers for voltage substitution calibration; 3) Versatile bridge completion/shunt calibration.

Automatic Bridge Balance

The Model 8000 offers an extremely convenient and accurate means for automatically balancing the input bridge circuit. The optional “Auto-Zero” circuit senses the polarity of the amplifier output and injects an isolated ratiometric correction voltage into the amplifier’s input to effectively null out any zero offset that may be generated by the bridge circuit. The auto-zero function is activated by a computer command. A front panel LED is illuminated while the auto-zero sequence is in progress.

Two ranges of Auto-Zero Adjustment are provided in both a Ratiometric and Zero Suppression Mode. In the Zero Suppression mode the computer has full control of the voltage insertion circuit in steps of 40 mV RTI or 1.8 mV RTI allowing the amplifiers’ output to be set anywhere from minus to plus full scale.


The 8000 features provisions for mounting up to 6 plug-in filters in any configuration of 2, 4 or 6 poles using Bessel or Butterworth characteristics. Cutoff frequencies range from 1 Hz to 100 kHz. Each filter is coded with an 8-bit identifying number, which is read and stored by the computer to assure data validity. Filters can be independently selected by the computer to provide either the same or different cutoff frequencies for the tape and galvo output.

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Last Updated: 18-Mar-2009  

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