Analog Computers

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VERO Analog Computer — Application Electronics (AC 46093)

This document is a translation of the original German-language publication.

Table of Contents (Inhaltsverzeichnis)

VERO ELECTRONICS — Analog Computer AC 46093

Overview

VERO ANALOG-COMPUTER — AC 46093
For education, demonstration, and optimization of measurement, simulation, and control systems.

Through the use of a new operational amplifier generation with offset voltage in the range of a few microvolts, BICC-VERO in collaboration with Prof. Dipl.-Ing. M. Zirpel of the Hochschule Bremen succeeded in developing an analog computer in quasi-briefcase form. The performance is comparable to conventional analog computers. Despite its compact circuit design, high computational accuracy is achieved. The use of wear-free, contactless analog switches ensures great operational reliability, high repetition frequencies, and long service life. The operating comfort is outstanding.

Features

  • The device has 6 integrators, 3 summers, 3 difference amplifiers, 2 multipliers, 12 coefficient potentiometers, and 4 diodes.
  • 3-position mode switch for operating mode selection:
    1. IC — Initial Condition (adjustable initial conditions)
    2. OP — Operate (compute)
    3. POT — Pot Set (potentiometer adjustment)
  • A digital voltmeter displays the settings of the ten-turn coefficient potentiometers.
  • In “Repetitive Computing” mode, solution curves can be displayed as flicker-free oscillograms.
  • Two or more analog computer units can be linked together for complex computing programs into a larger computing unit. One analog computer (master) assumes the control function for the remaining analog computers switched as slaves. For this, the master-slave switch on the device is set to the appropriate position.
  • All computing elements are located on a single-sided populated large board (see Fig. 2) — no long leads or cable harnesses: interference-proof.
  • Supply voltages: ±8 V for operational amplifiers, ±5 V for reference, and ±12 V for multipliers, located on a separate power supply board.
  • Clear plug-in/programming field (see Fig. 3).
  • The programming field contains gold-plated 2 mm mini-jacks.
  • Delivery includes a laboratory cable set with 2 mm banana plugs for a total of 55 connections.
  • An aluminum frame case with combination locks ensures secure packaging.

Computing Elements (Rechenelemente)

3 Difference Amplifiers (Differenzverstärker)

The computing elements are designed as difference amplifiers. With them, important operational amplifier basic circuits can be realized more simply than with summers, e.g., non-inverting amplifiers, impedance converters, and Schmitt triggers. Difference amplifiers can — after connecting the non-inverting input to ground — naturally also be used as summers.

All Integrators

All integrators can also be used as summers or inverters without additional components.

Summers

The summers can be converted into integrators by external wiring with a plug-in capacitor.

Operating Modes (Betriebsarten)

The simple control circuit (Fig. 2) enables three operating states selectable via the mode switch with three positions:

  • POT — Potentiometer Adjustment
  • IC — Initial Condition
  • OP — Operate

In the Operate mode, single-shot and repetitive (REP) operation can be selected by switch. Since very short integration times (1 ms) can also be set, flicker-free oscillograms of transient functions can be generated in repetitive mode. Computing and pause times are specified by an astable multivibrator (OV1) with a pulse-to-pause ratio of 5:1 and a frequency adjustable between 1 and 100 Hz.

In Initial Condition mode, the integrator initial values are set (see Integrator). The computing circuits are also assembled in this mode.

Precise setting of coefficient potentiometers is done in Potentiometer Adjustment mode. The potentiometer input is connected to the positive reference voltage; the output is connected to the digital voltmeter (see Coefficient Potentiometers).

Operational Amplifier (Operationsverstärker)

The most important building block of the analog computer is the operational amplifier. With input and feedback circuitry, mathematical operations such as addition, subtraction, differentiation, and integration can be performed with it — depending on the circuit. Due to its extraordinarily versatile application possibilities, the operational amplifier has central importance in analog technology. The compact analog computer also offers possibilities for practical testing of common basic circuits.

The compact computer contains high-quality integrated operational amplifiers in CMOS technology. They are permanently short-circuit-proof and are characterized by particularly low offset voltage (approx. 1 µV) and low input bias current (approx. 10 pA).

Adder (Addierer)

The adder schematic uses the well-known inverting summing amplifier topology. The inverting inputs are each connected with resistors (referred to as HIGH inputs). The output equation is:

UA = −(U1 + U2 + U3 · 10 + U4 · 10 + U5)

(or similar weighted combinations depending on configuration)

Integrator (Integrierer)

The integrator has resistive input circuitry (summing input) and a capacitor in the feedback path. In Initial Condition mode (switch position IC), the capacitor voltage is set to a specific initial value before each computation. For this, the inverse voltage −Ua(0) is applied to the integrator jack “IC”.

The integrator can also be used as a summer or inverter (no additional components needed).

Example — Integrator T = 1 sec
Example — Integrator T = 10 ms
Example — Summer K = 1

Equation: UA = −∫(U1 + U2 + U3·10·U4 + 10·U5) dt + Uic

Multiplier (Multiplizierer)

The integrated four-quadrant multiplier is adjusted with an additional circuit for the ±5 V signal level.

Equation: UA = (1/10) · U1 · U2 (voltages in Volts)

The multiplier can also be operated as: quadrater, square-rooter, and divider. Circuit examples are compiled in the following overview:

CircuitEquation
QuadraterUA = 0.2 · UE²
Square-rooterUE = 2.24 · √
DividerUA = 5 · UX/UY

Coefficient Potentiometers (Koeffizientenpotentiometer)

12 ten-turn coefficient potentiometers are available for precisely setting coefficients. The digital voltmeter (DVA) is connected to the potentiometer output for setting. In Potentiometer Adjustment mode, the potentiometer input is connected to the positive reference voltage (+5 V), and the potentiometer output is read by the digital voltmeter.

The coefficients are not only used for POT mode settings (potentiometer settings) but also for dependent amplitude measurements.

X-Y Deflection
The programming field provides a clear overview of all connections.

Timing and Repetitive Operation

  • Operating/computing time: adjustable, 1 ms … 300 s
  • Pause time/computing ratio: 1:5 (pulse-to-pause)
  • Repetitive frequency: adjustable 1 to 100 Hz for flicker-free oscillograms

The solution curves are displayed on an oscilloscope. With “Single Shot” mode, the result is non-repetitive (single capture), whereas in repetitive operation the X-Y plotter or oscilloscope can display the results continuously.

Master-Slave Operation

Multiple analog computer units can be linked for complex computing programs. One analog computer (Master) controls the other units (Slaves). All analog computers must be connected (signal busses AS1 and AS2). The slaves must have their mode switch set to slave position. Only the Master’s switch actually determines the operating mode.

Technical Specifications (Technische Daten)

ParameterValue
Mains supply220 V / 50 Hz
Power consumptionapprox. 30 W
Op-amp supply voltage±8 V
Reference voltage±5 V (max. ±15 V)
Multiplier supply±12 V
Shortest integration time0.8 ms typ.
Input currentapprox. 3.5 nA
Metal film precision resistors—
Integration capacitorsbetter than ±0.1%
Output current (op-amp)max. 2.5 mA / summer & integrator
Summing junction resistance1 MΩ
Reference voltage accuracy±1% (better ±0.5%)
High/Low logic levelsprogrammable
Large board dimensions429 × 212 × (H×L×B) mm aluminum
Power supply board429 × 217 × 35 (H×L×B) mm aluminum
Aluminum frame/case488 × 268 × 135 mm (H×L×B)
Weightapprox. 4.5 kg

Application Example: DC Motor Speed Control

Case Study: Speed control of a separately excited DC shunt motor

A linearization of the characteristic curves at the operating point is assumed.

System overview:

  • LV: Power amplifier
  • M: Motor
  • T: Tachogenerator
  • n: Speed

Signal flow diagram leads to the analog computer circuit. The analog computer circuit is created from the signal flow diagram.

Parameters used:

  • Ka = 262
  • T1 = 1 sec, T2 = 5 sec, Tr = 3.62 sec
  • c1 = 0.2, c2 = 0.262, c3 = 0.276, c4 = 0.2

Transient functions:

  • Command response (Z = 0): The controlled variable follows the reference variable quickly and with little oscillation.
  • Disturbance response (w = 0): The effect of the disturbance variable (Z) is compensated quickly and with little oscillation.

Application Areas (from back page index)

  • Electrotechnology
  • Electronics
  • Static electricity
  • Physics
  • Mathematics
  • Biology / Bio-medicine
  • Biology

Document: VERO ELECTRONICS VER 09/85.115-44214G · Printed in West Germany · BVE315

[Translation covers the first 12 pages (entire document); translation complete.]