Analog Computer DORNIER 240 — Technical Description

This document is an English translation of the original German brochure/description for the Dornier 240 analog computer (language: de).

General
Fields of Application
Main Features
Full Configuration
Computer Architecture
Patch Panel Layout and Arrangement of Computing Elements
Summing Integrators
Summers
Multipliers
Function Generators
Potentiometers
Logic Supplement

1. General

The DORNIER 240 is a fully transistorized precision desktop analog computer with a computing voltage of 10 volts. In full configuration it contains 49 computing amplifiers.

All computing elements are implemented as parts of a modular building-block system, so that a variable configuration of the DORNIER 240 is possible to match a wide variety of problems. Likewise, the 240 computer can initially be purchased in a cost-effective basic configuration and later expanded to the full configuration.

The DORNIER 240 is equipped with a series of technical special features that are otherwise only found in larger installations. This makes the DORNIER 240 capable of solving even complex systems of differential equations. Programming remains simple, since completely novel computing components — such as digital potentiometers — are available to the programmer.

For programming and operating the DORNIER 240 analog computer, no electronic knowledge whatsoever is required, since both the control panel and the patchboard are arranged simply and in an easily understandable manner.

The DORNIER 240 is thus excellently suited for solving systems of differential equations in all areas of science and technology.

2. Fields of Application

Analog computers are used wherever the solution of differential equations is required. They enable, among other things, real-time simulation of dynamic systems and reduce the effort for time-consuming, costly, and hazardous practical experiments.

Typical analog computer problems arise in the following areas:

Control Engineering: Simulation of control systems, parameter studies, frequency response measurements
Aerospace: Simulation of flight vehicles
Medicine and Biology: Simulation and investigation of biomedical processes
Automotive Industry: Vibration problems, investigation of driving behavior
Nuclear Engineering: Reactor simulations
Chemistry: Simulation of chemical reactions
Education: Demonstration of dynamic processes
Measurement Engineering: Level matching, construction of filters

3. Main Features

Expandable from an affordable initial configuration to a high-performance computer for complex simulations.
Interchangeability of all computing elements between the DORNIER 240 and DORNIER 720.
Absolute continuous short-circuit immunity of all components.
Fully transistorized amplifiers with bandwidth exceeding 350 kHz.
Parabola multipliers with built-in input inverters.
Adjustable function generators with built-in amplifiers.
Individually controllable integrators.
Electronic operating mode control with TTL logic.
Built-in digital supplement with TTL logic elements.
Built-in digital voltmeter with 4½ digits.
Amplifier recovery time from fully saturated overload less than 1 millisecond.
Addressability of all computing elements, integrator summing points, and external connection lines.
Repetition frequency adjustable from 0 to 78 Hz (pause 3 ms, compute 10 ms).
Selection of smaller integration capacitors by pushbutton or individual control.
Additional amplifier for generating a ramp as deflection voltage for recorders and as clock for repetitive computing.
Convenient digital clock generator for controlling 3 repetitive operating modes.

4. Full Configuration

Component	Config 1¹	Config 2²
Total amplifiers	40	56
— of which Summing Integrators	12	12
— Summers	12	12
Freely available Inverters (Multipliers)	8	—
Non-freely available Inverters (Multipliers and Function Generators)	8	32
Hand potentiometers	24	24
Digital potentiometers (17-bit)	2	2
High-accuracy multipliers with input inverters	4	—
Standard multipliers complete with amplifiers	—	8
Adjustable function generators	4	4
Fixed function generators (sin x, cos x, x², log x)	4	4
Limiters	4	4
Comparators	6	6
Function relays	2	2
Function switches	2	2
Freely programmable resistor networks (1, 1, 10, 10)	12	12
External connection lines (trunks)	26	26
Flip-flops	8	8
Gates	11	11
Monostable multivibrators	2	2
Logic function switches	3	3
Counters	1	1
Freely available amplifiers when all nonlinear components in use	16	20

¹ With high-accuracy multipliers
² With standard multipliers

5. Computer Architecture

The basic unit of the DO 240 contains all power supplies, the complete wiring, and the display and control panel. Above the display and control panel is the interchangeable programming board, behind which the network modules for receiving the computing elements are arranged. Above this is the potentiometer panel with up to 24 hand potentiometers. In the upper right portion of the computer there is provision for installing a logic supplement, while next to it a slot exists for either a digital voltmeter or a quartz-stabilized repetitive clock generator. When the clock generator is installed, a standard digital voltmeter can be connected via sockets on the rear of the computer.

Display and Control Panel

The display and control panel in the lower part of the DORNIER 240 contains all the display and control elements required for operation.

The overload indicator panel (left of the voltmeter) shows the state of the 6 comparators as well as the overloaded amplifiers.

Operating mode control is accomplished via the pushbuttons POT (set potentiometer), AB (initial condition), HT (hold), DR (continuous compute), and RR (repetitive compute). Two types of integration networks are available for the operating modes. Either DR and AB are controlled electronically and HT by a relay, or all three operating modes are controlled electronically. For repetitive operation the DORNIER 240 is equipped as standard with a clock generator that permits repetition frequencies between 0 and approximately 78 Hz.

Instead of the digital voltmeter, a digital clock generator can be installed that cyclically drives the operating modes AB, DR, and HT with adjustable times from 1 µs to 99 s each.

The X10 and X100 keys accelerate the program timing. The RR key accelerates the program by a factor. Individual selection of time constants for individual integrator pairs on the patchboard is still possible.

The STT (static test) key switches +10 V reference voltage to the sockets labeled STT on the patch panel, which can be used as test voltages for static tests.

The REMOTE CONTROL switch configures the computer as a slave computer of another DORNIER 240 or 720. The keys labeled 1 and 2 are the function switches available on the patchboard, while keys 1R and 2R allow manual control of the function relays available on the patchboard.

The VOLTMETER FUNCTION rotary switch enables checking of supply voltages using the voltmeter. At the same time, this switch selects the measurement range of the voltmeter; in the +POTREF or −POTREF positions, the voltmeter is switched for precise compensation measurements against the ten-turn auxiliary potentiometer.

The AUXILIARY AMPLIFIER switch controls the operating mode of the standard-installed auxiliary amplifier. In positions INT SP ×1 or INT SP ×0.1, the amplifier measures with gains of 1 or 0.1 the summing-junction voltage of a selected integrator. In position STSF (static setting of function generators), the amplifier serves together with the auxiliary potentiometer as a setting amplifier for the variable function generators located in the socket of the computer. In operating mode RAMP, the amplifier delivers a one-time ramp at the start of DR mode, whose slope is set via the auxiliary potentiometer. In position REP. OPER., the auxiliary amplifier generates a rapidly repeating ramp. In both cases the amplifier output voltage can be used as a time-deflection voltage for a recorder.

Via the two ADDRESS and GROUP/INDIVIDUAL SELECT rotary switches, any desired computing element can be selected and its output voltage displayed on the analog and/or digital voltmeter. The GROUP SELECT switch determines the type of element to be selected (potentiometer, amplifier, etc.), and the ADDRESS switch gives the number of the element and the sector concerned.

6. Patch Panel Layout and Arrangement of Computing Elements

The programming field is divided into two identical halves (Sector 1 and Sector 2).

The computing elements are located in up to six network modules, three of which form each sector. Within a sector, the two outer modules (1 and 3, or 4 and 6) are identical; the middle module (2 or 5) is similar to the two outer ones.

The module slots can be equipped as follows:

Slot 1: Module 1.005 (Part No. 20001Mo1)
Slot 2: Module 1.105 (Part No. 20001Mo2)
Slot 3: Module 1.005 (Part No. 20001Mo1)
Slot 4: Module 1.005 (Part No. 20001Mo1)
Slot 5: Module 1.105 (Part No. 20001Mo2)
Slot 6: Module 1.005 (Part No. 20001Mo1)

The modules are connected to the interchangeable programming board via gold-plated contact springs of beryllium bronze and contain all the facilities required for operation of the computing elements, such as circuit resistors, relays, etc. The following components can be inserted in the individual socket positions (numbered 1 to 8 from below):

Module 1.005:

Positions 1–4: 1 summer each, and 1 summer or summing integrator each
Position 5: 1 comparator and 1 switching network for two integrators
Position 6: 1 high-accuracy multiplier
Position 7: 2 fixed function generators (sin x, cos x, log x, x²)

Module 1.105:

Positions 1–4: 1 summer each, and 1 summer or summing integrator each
Position 5: 1 comparator and 1 switching network for two integrators
Position 6: 1 17-bit digital potentiometer
Position 7: 2 standard multipliers

In addition, the modules have patch panel connections for reference voltages, potentiometers, integrator control lines, external connection lines, etc.

7. Summing Integrators

The simplified circuit of a summing integrator in its operating form as integrator is shown in the following figure. [Circuit diagram — see original.]

Each summing integrator slot includes a freely programmable resistor network whose summing point is designated SPW. Connecting SP to SPW increases the number of integrator inputs to five unity-gain and three decade inputs. These resistor networks are of course also freely usable in other configurations (e.g. with other amplifiers).

The switches S1, S2, and S3 (shown as mechanical contacts) are actually purely electronic switches with the following truth table:

H	ES	S1	S2	S3	Operating Mode
0	0	0	1	1	Hold (HT)
0	1	0	0	0	Initial Condition (AB)
1	0	1	1	1	Continuous Compute (DR)
1	1	1	1	0	Initial Condition (AB)

The H and ES sockets are labeled with the respective amplifier number and brought out at the rear end of each integrator. Directly below are the output sockets of the bus lines controlled by the AB, DR, and HT pushbuttons (labeled DR and HT). Each integrator whose ES input is connected to the DR socket and H input to the HT socket follows the pushbutton commands.

Switching the time constants, i.e. the integration capacitors, is accomplished via the X10 and X100 sockets with the following truth table:

X10	X100	Capacitor	Time Scale Factor
open	open	10 µF	1
grounded	open	1 µF	10
open	grounded	0.1 µF	100
grounded	grounded	0.01 µF	1000

The formula implemented is: ∫(x1 + 10·x2) dt

Below the X10 and X100 sockets are also the outputs of the bus lines controlled by the X10 and RR (repetitive compute) keys.

Thus the integrators are individually controllable in operating mode and pairwise in time constants. An exception is the integrators in the middle module of a sector, where the operating modes are individually controllable but time-constant control is permanently wired unconditionally through the RR and X10 keys — this does not, however, lead to any reduction in flexibility.

8. Summers

Two types of summers exist:

Summers on slots 1, 2, 9, and 10 of a sector (strongly simplified circuit shown in original)
Summing inverters on slots 5 and 6 of a sector (strongly simplified circuit shown in original)

As with the summing integrators, the summing point SP of the summers is freely accessible. This means that together with freely programmable resistor networks, inputs of values 0.1, 0.5, 5, 2, 10, etc. can also be achieved.

Each summer can also be operated as an open amplifier. In this case the socket V⁻⁹⁹ is used, which must be grounded for this purpose.

The summers are equipped with 10 kΩ resistors because on one hand the high-accuracy multipliers require an output amplifier with 10 kΩ feedback, and further the fixed function generators require an amplifier wired with 10 kΩ resistors for their operation.

9. Multipliers

Two types of multipliers exist: the standard multiplier and the high-accuracy parabola multiplier.

The standard multiplier is equipped with all required amplifiers. The parabola multiplier is equipped with two input inverters and additionally requires a 10 kΩ-feedback output amplifier for operation.

Via the output amplifier, the operation x·y + ΣZ is also possible, where ΣZ represents the variables present at the inputs of the output amplifier.

10. Function Generators

The following fixed function generators are available:

y = √x (x ≥ 0)
y = x² (x ≤ 0)
y = log x (x > 0)
y = log(−x) (x < 0)
y = sin x
y = cos x

The fixed function generators require for their operation a 10 kΩ-feedback amplifier or (depending on operating mode) an open amplifier. Each function generator can also be used to represent the inverse function:

y = √x
y = 10^x
y = arcsin x
y = arccos x

In addition to the fixed function generators, up to four adjustable function generators (hereafter abbreviated as VDFG = Variable Diode Function Generator) are located in a drawer below the control panel, for simulating mathematically non-closed-form representable functions (such as measured curves, etc.). Each VDFG enables the approximation of such curves by a polygon. For this purpose each VDFG has ten adjustable breakpoints as the vertices of the polygon. Furthermore, the slope of individual segments can be set.

A change in the overall gain of the VDFG via a special potentiometer stretches the function in the y-direction.

For simulating complex curves, two VDFGs can be connected in parallel, increasing the number of breakpoints to 20.

Each VDFG is equipped with the amplifiers required for its operation, so no additional amplifier needs to be used.

11. Potentiometers

The DO 240 can be equipped with up to 24 hand potentiometers. Each hand potentiometer is implemented as a ten-turn wire-wound potentiometer with scale. The wiper is protected against destruction by short-circuit or reverse voltage by an overcurrent protection. Setting is accomplished via a digital voltmeter (if installed or available as a separate instrument) or via a compensation circuit using the voltmeter and reference potentiometer in the display and control section.

12. Logic Supplement

On request, a logic supplement is installed in the DORNIER 240, whose full configuration is defined earlier in the document.

The logic supplement has its own special operating mode control via the AB and ASYN keys. With the ASYN key, all 8 flip-flops can be switched between synchronous (clocked) and asynchronous (unclocked) operation. The AB key controls the “initial condition” and “compute” operating modes. In initial condition mode, the flip-flops can be set to a defined initial state via their indicator lamps implemented as pushbuttons. This initial state is re-entered whenever the logic is switched to the AB operating mode. Resetting all flip-flops before the start of a new computation run is thus unnecessary. Pressing the erase keys clears individual flip-flop groups. The general LO key clears all flip-flops and counters.

The eight indicator lamps of the 8-bit down counter are likewise implemented as keys and labeled according to their binary weight. Via these keys, the counter can be preset.

On the logic programming board there are five control lines for operating mode control of the analog part by the logic. Likewise, via two of these control lines the operating mode control of the logic can also be effected.

Instead of the digital voltmeter, a convenient digital clock generator can be installed, whose output signals both control the operating modes AB, DR, and HT of the analog part and are also available separately on the logic programming board. The duration of the individual signals AB, DR, and HT (and hence the time the computer remains in these operating modes) is adjustable via thumbwheels in the range between 1 µs and 99 s. After switching off the internal 1 MHz clock, the clock generator can also be used as a triple decimally adjustable counter. In each operating mode, the current count of the running counter is shown on the nixie tube display.