Analog Computers

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EAI Digital Measuring System Series 6200 — and Related Topics (EAI Report No. 011, March–April 1967)

This document is an English translation of the original German-language EAI-Report Nr. 011, Marz–April 1967, published by EAI Electronic Associates GmbH, Aachen.

EAI Digital Measuring System, Series 6200

The EAI Digital Measuring System 6200, presented here for the first time, is sure to attract interest, not least because of its attractive price combined with remarkable versatility. Drawing on the extensive experience of Electronic Associates in the field of digital measurement technology, a family of instruments has been developed that offers an optimum combination of performance, accuracy, reliability, and cost-effectiveness.

Compact in its external dimensions, the instrument can be quickly and easily adapted to different measurement tasks by inserting an appropriate plug-in module. It is therefore equally well suited wherever different measurement tasks follow one another in succession — for example, the measurement of DC voltage, time intervals, frequency, etc. All circuits are implemented in semiconductor technology, which guarantees low power consumption and maximum operational reliability.

The EAI Digital Measuring System 6200 consists of the following assemblies:

1. Base Chassis, Type 6200

The base chassis contains a numerical display panel, the power supply, high-speed counting circuits, the display clock generator, and the switching logic to select between the two plug-in modules the chassis can accommodate.

Display: 4-digit, consisting of 3 true digits plus one overflow digit; decimal point positions automatically according to the selected range; display triggering continuously adjustable from 0.2 to 6 sec; automatic indication of polarity for DC voltage.

Control: Display can be reset to zero automatically or by pushbutton; rotary switch for selection of the desired plug-in module.

Input: Signals from 0–10 MHz, depending on the type of measurement, can be processed.

Circuitry: Silicon semiconductor technology; integrated circuits; inputs floating; chassis grounded.

Mains connection: 115/230 V ±10%, 50–400 Hz.

Environment: 0–60 °C at 0–90% relative humidity.

Dimensions: Height 7”, Width 8½”, Depth 11”.

Price: DM 1,530 (undutiable) / DM 1,805 (dutiable).

2. DC Integrating Digital Voltmeter Module, Series 6201

The digital voltmeter is inserted as a plug-in into the base unit 6200. It operates on the integrating principle, so that accurate measurements remain possible even in the presence of significant interference voltages. The chopper for suppressing zero-point drift is fully electronic, which results in a shorter time constant. This ensures a short response time for step-function inputs. The high input impedance prevents distortion of the measurement result due to excessive loading of the measurement point. For particularly critical measurements, a low-capacitance probe is provided.

5 DC voltage ranges:

  • 0–140.0 mV max.
  • 0–1.400 V max.
  • 0–14.00 V max.
  • 0–140.0 V max.
  • 0–1000 V max.

Resolution: 100 µV

Accuracy: ±0.1% of full-scale ±1 digit

Range overrange: 40%, except 1000 V range

Input impedance: Direct: 10 MΩ constant; via probe: 10 MΩ + 1 MΩ from probe

Input: Floating or grounded; ±500 V DC between input and chassis ground permissible

AC rejection: 80 dB at 60 Hz; 90 dB at 120 Hz

Conversion time: approx. 100 ms

Response time: For a step-function input equal to the maximum value of the selected voltage range, 99.9% of final value reached after 700 ms.

Polarity: Automatic display of ”+” or ”−”

Overload protection: Up to 1000 V DC can be safely applied regardless of the range selected.

Temperature range: 0–50 °C; full accuracy 15–35 °C

Power supply: Via rear connector from base unit 6200.

Dimensions: Height 2⅛”, Width 8⅛”, Depth 9¼”

Price: DM 1,080 (undutiable) / DM 1,275 (dutiable).

3. Digital Counter Module, Series 6202

The counter plug-in is used for the accurate measurement of frequency, time interval, and period. The measurement result is likewise displayed digitally on the base unit. Integrated circuits combined with a quartz-controlled oscillator ensure high stability.

Frequency measurement:

  • Range: 0–10 MHz
  • Accuracy: ±0.005% ±1 count
  • Input impedance: 1 MΩ; 30 pF shunt capacitance
  • Trigger sensitivity: 100 mV

Period measurement:

  • Range: 1 µs–1000 s
  • Resolution: Dependent on selected range (1 µs max. ±1 digit)

Time interval measurement:

  • Range: 1 µs–1000 s
  • Resolution: Dependent on selected range (1 µs max. ±1 digit)

Frequency standard: 1 MHz quartz oscillator ±0.005%

Temperature range: 0–60 °C; full accuracy 15–35 °C

Power supply: Via rear connector from base unit 6200.

Dimensions: Height 2⅛”, Width 8⅛”, Depth 9¼”

Price: DM 945 (undutiable) / DM 1,115 (dutiable).

4. AC Converter Module, Series 6203

This plug-in, used in conjunction with the DC Digital Voltmeter plug-in Type 6201, enables AC voltages to be measured over a wide frequency range with high accuracy. The converter output provides a DC voltage proportional to the RMS value of the sinusoidal input voltage. This DC voltage is digitized and displayed as a 4-digit decimal number.

4 AC voltage ranges:

  • 0–1 V rms
  • 0–10 V rms
  • 0–100 V rms
  • 0–300 V rms

Frequency range: 20 Hz–100 kHz

Accuracy:

  • 0.2% for 20 Hz–10 kHz
  • 0.3% for 10 kHz–100 kHz

Input impedance: 1 MΩ; 30 pF shunt capacitance

Power supply: Via rear connector from base unit 6200.

Dimensions: Height 2⅛”, Width 8⅛”, Depth 9¼”

Price: DM 1,125 (undutiable) / DM 1,325 (dutiable).

(By Dipl.-Ing. H.-W. Bock, Sales Engineer, EAI-GmbH)

An Analog Computer Sample-and-Hold Circuit for Coordinate Transformation

The development of electronic mode control (EMC) and parallel logic has opened up an entirely new computing technique for the modern high-speed analog computer: the parallel subroutine technique. To solve a problem, two or more subprograms are set up that operate at different computing speeds and are interleaved into a single overall program.

The application of this solution method very often yields a considerable saving in computing components, particularly nonlinear components such as multipliers, function generators, and resolvers. These savings are especially pronounced in problems where functions that are implicitly defined by analytical expressions must be explicitly generated. The following describes methods for coordinate transformation — polar-to-Cartesian, Cartesian-to-polar, and axis rotation — that exemplify the subroutine technique.

1. Conversion of Polar to Cartesian Coordinates

Given the radius vector R and the polar angle θ, the relationship is:

X = R·cos θ,    Y = R·sin θ

To generate the trigonometric functions, the oscillation equation

d²z/dt² = −ω²z

is solved. The solution is:

z = A·cos ωt + B·sin ωt
(1/ω)·dz/dt = A·sin ωt − B·cos ωt

With the initial conditions z(0) = A = R and (1/ω)·dz/dt(0) = −B = 0, the solution reads:

z = R·cos ωt
(1/ω)·dz/dt = R·sin ωt

Examining this solution at the moment when ωt = θ yields the desired transformations:

z = R·cos θ = x
(1/ω)·dz/dt = R·sin θ = y

The computing circuit is shown in Fig. 1a. As a subroutine, the trigonometric functions are generated in the fast repetitive mode by the well-known oscillator circuit and fed to the sample-and-hold elements. Track-and-hold units TS 1 and TS 2 are connected so that they can follow the output voltages of Integrator 1 and Amplifier 3. The sampling condition ωt = θ is realized by a comparator that compares the input quantity θ with a ramp function ωt also generated in the fast repetitive mode.

When both values are equal, the comparator switches the TS units so that the value present at TS 1 and TS 2 at that instant is stored and transferred to TS 3 and TS 4. The solution function obtained at the output of TS 3 and TS 4 is not a continuous curve but a staircase approximation. This approximation improves the more frequently the input quantity θ is sampled by the ramp ωt. The higher the frequencies contained in θ, the higher the sampling rate must be. With a computation time ratio of approximately 1:1000 between main program and subroutine, the resolution is fine enough that the steps in the solution function are no longer visible.

Note that θ must not become negative. If negative values are to be permitted, an additional comparator and an electronic switch can be used to add 2π to θ, restoring positive values according to the relation:

−θ + 2nπ → θ,    n = 1, 2, 3, …

2. Conversion of Cartesian to Polar Coordinates

According to Fig. 2b, the relationship is:

R = X·cos θ + Y·sin θ
0 = X·sin θ − Y·cos θ

In the fast repetitive mode the oscillation equation is again solved. With initial conditions A = X and B = Y, the solution is:

z = X·cos ωt + Y·sin ωt
(1/ω)·dz/dt = −X·sin ωt + Y·cos ωt

The sampling condition (dz/dt = 0) is realized by comparison with ground potential. At the moment of switching, ωt = θ, and:

z = X·cos θ + Y·sin θ = R

In this transformation the saving in computing elements is particularly striking. A solution using conventional methods would require 11 amplifiers, 2 sin-cos function generators, and 4 parabolic multipliers.

3. Rotation of Coordinate Axes

The rotation of a rectangular coordinate system x, y through an angle θ is described (see Fig. 3b) by:

u = X·cos θ + Y·sin θ
v = Y·cos θ − X·sin θ

The repetitively operated oscillator (Fig. 3a) delivers, with initial conditions A = X and B = Y, the functions:

z = X·cos ωt + Y·sin ωt
(1/ω)·dz/dt = −X·sin ωt + Y·cos ωt

With the sampling condition ωt = θ, the desired transformation is obtained:

z = X·cos θ + Y·sin θ = u
(1/ω)·dz/dt = −X·sin θ + Y·cos θ = v

The associated circuit (Fig. 3a) differs from Fig. 1a only in a different choice of initial conditions.

(By Dipl.-Ing. K.H. Hortenbach, Applications Engineer, EAI-GmbH)

The Magazine for the Brush Mark 250 Recorder

Readers of EAI-Report No. 010 (January/February 1967) who are interested in direct-writing recorders will already know that this section refers to the removable paper magazine of the Brush Recorder Mark 250. Please contact the EAI-GmbH office for further information (Tel. 0241/26 042).

Logarithmic Preamplifier for Brush Multi-Channel Recorders, Type Mark 200, 240, 250 and 280

The Brush preamplifier, Model L3 4314 00, enables signals with a wide dynamic range to be recorded in a logarithmic scale without changing the input scale. This makes it particularly interesting for the investigation of filter characteristics of active and passive networks and transmission paths in general measurement technology, acoustics, sonar technology, etc.

The logarithmic preamplifier, which is matched to the static and dynamic characteristics of the Brush recorders, can also be used as a linear amplifier by switching. Four operating modes are available:

  1. AC Log: The amplifier output is proportional to the logarithm of the RMS value of the input voltage. Nine 50 dB measuring ranges in ratios of 10 dB, from 10 mV rms to 100 V rms full-scale are available. Maximum roll-off of 1 dB at 100 kHz. Lower cutoff frequencies of 20, 100, and 500 Hz are selectable via filters. Sensitivity: 1 dB/division.

  2. AC Linear: The log network is bridged. Nine linear scale settings from 200 mV/division to 2 V/division. Frequency response as in mode 1.

  3. DC Log: Output voltage proportional to the logarithm of the input signal. Five measuring ranges in ratios of 10 dB, from 1 V to 100 V full-scale; 3 dB cutoff frequency at 400 Hz.

  4. DC Linear: As mode 1 linearly. Frequency response as in mode 2.

Price (ab Aachen): DM 4,390 (undutiable) / DM 5,170 (dutiable).

(By Dipl.-Ing. A. Bento, Sales Engineer, EAI-GmbH)

EAI Class B Equipment and Systems

EAI is currently in a position to offer the following EAI-PACE equipment as “Class B” systems:

  • 1 unit EAI-PACE Analog Computer, EMC, Type TR-48/58
  • 1 unit EAI-PACE Desktop Analog Computer, Type TR-20
  • 1 unit DATAPLOTTER, Model 3110
  • 1 unit VARIPLOTTER, X-Y Plotter, Type 1110

Note: Class B equipment consists of units that have been used for some time in one of EAI’s computing centers in the USA or Europe and are offered at reduced prices under normal warranty and delivery conditions.

EAI 9000 Scientific Computing System Characteristics

(European Division, Centre International, 22nd Floor, Place Rogier, Brussels, Belgium)

The EAI 8800 Analog Computer: 60-integrator capacity, 125 kc bandwidth.

The EAI 8400 Digital Computer: 32-bit word length plus 2 executive bits; 2 Mc synchronous logic; 7.35 µsec typical floating-point multiply; 64K memory capacity; 7 hardware index registers.

The EAI 8900 Interface: 32×32 expandable to 128×128 conversion channel capacity; 65 kc analog-to-digital word rate; single or double-buffered digital-to-analog channels; quad-rate and time-multiplexed analog-to-digital channels; expandable interrupts, function lines, and status lines terminated on the logic patch panel.

EAI 8900 Software: FORTRAN IV; Macro Assembler; SPECTRO line assembly system; Monitor and Real-Time Scheduler; HYTRAN 5 simulation language; HYTRAN function generation programs; iterative programs; numerical integration programs; analog control and readout programs.

EAI Events Calendar (1967)

  • 24–25 April 1967, Munich: Lecture series with TR-48/58 – DES-30 Hybrid-Analog Computer demonstration (Hotel “Regina”, Munich)
  • 29 April – 7 May 1967, Hannover: Hannover Trade Fair, Hall 10, Stand 181 (Fa. Multi-Contact AG, Switzerland)
  • 10 May 1967, Freiburg i.Br.: Lecture series with TR-48/58 – DES-30 Hybrid-Analog Computer demonstration (Kolpinghaus)
  • 11 May 1967, Karlsruhe: Lecture series with TR-48/58 – DES-30 demonstration (Parkhotel)
  • 17 May 1967, Hannover: Lecture series with TR-48/58 – DES-30 demonstration
  • 18 May 1967, Braunschweig: Lecture series with TR-48/58 – DES-30 demonstration
  • 31 May 1967, Hamburg: Lecture series with TR-48/58 – DES-30 demonstration (Hotel Reichshof)
  • 5–6 June 1967, Frankfurt/Main: EAI Colloquium “Digital Data Recording Systems MDP-200” (Hotel Intercontinental)
  • 7–9 June 1967, Frankfurt/Main: EAI Symposium 1967 (Hotel Intercontinental)
  • 19–23 June 1967, Frankfurt/Main: Exhibition at US Trade Center, Frankfurt/Main (Telemetry)
  • 9–13 October 1967, Munich: EAI Hybrid/Analog Computer Course (Hotel “Regina”) — course program available on request.

New EAI Publications

  1. Catalog/Price List: Multi-channel recorders “Brush – Recorder –”
  2. “Elimination of Noise in Low-Level Circuits” — Brush study
  3. Data sheet: EAI X-Y Plotter VARIPLOTTER
  4. Overview list: EAI Application Studies