First Acoustic Camera
Funktionen PSI-Tools
Software PSI-Tools

Hardware for PSI-Tools

16-Channel Preamplifier

Find here some images of the hardware (until 1997), used to make records for first electric and acoustic interference integrals (acoustic images, nerve images and -films).

The Toshiba-laptop we used was one of the very first in the world. And this wonderfull compact sized Toshiba from 1996 was very expensive, it costs some thousand Deutsche Mark (DM). It had a docking station with a full-Size AT-bus slot. Perfect for our full-size ADC-card WIN30DS with 16 channels! The ADC-card contained no Nyquist-filters. So it was necessary, to develop a preamplifier box containing the 16 filters.

The fat flex-cable in the background connects the 16-channel preamplifier box (right). It carried the 16 analog channels and control signals to set the filter-circuits.

The preamplifier contained for each channel the ADC-aliasing filters and adjustable highpass and lowpass filters.

Technical details:

(Remark 2023: You could ask, why it is necessary, to develop a big preamplifier with 32 filter switches per channel?
If one gets an analog signal with a bandwith higher the Nyquist-frequency fs/2, the sampling produces additional noise by frequency aliasing. So each ADC has to band-limit the incomming signal using a low pass filter below fs/2.
Today we use ADCs working with ΔΣ-technology. They include the band limiting filter. Our WIN30-DS-card contained an ADC without any filter. So we had to implement a filter for each channel. Too I would be sure, that we will not get any aliasing effects only solveable with additional analog filter hardware.

16-Channel Analog-Digital-Converter Card

The 12 bit analog-digital converter UEIDAC WIN30-DS for 16 channels was a full sized ISA-board within the personal computer (IBM-PC-AT i486). 4 ADC-cards (64 channels) were possible. The ADC contained no Nyquist-filter. Sample rate max. 50 kHz (100 kHz) per channel, dependend of the PC-ISA-Bus used.

8-Channel Preamplifiers (1995)

I wrote the book "Neuronale Interferenzen" (Link) in the hope, to get spike-like nerve signals from everywhere in the nerve-systeme, to reconstruct them like in the thumb-experiment. So an ADC with a (for 1994) very high sampling rate (50/100 kS/sec) and 16 channels was ordered, the UEIDAQ WIN30DS, and "high frequency" EEG-preamplifiers were developed (EEG-amps had in tis time samplerates of max. 2 kS/sec).

Unfortunately we did not find any rests of spike-like signals from Electro-Encephalograms (EEG) or Electro-Cortikograms (ECoG) we got.

So what to do? We had to expand our perspective. I ordered 8 electret-microphones at Conrad and built an adapter for the amplifier. And within two weeks we had the first acoustic image (Aug. 23, 1994) - with very poor quality and a bug in the color table, but it was the worldwide first acoustic image (of passive type) (Link). This changed everything:

It brought lots of questions: "Did you ever heared something about an acoustic image? No?" and "How many acoustic institutes worldwide would research on such things?"

We found, that 1994 were approximately 1800 acoustic institutes in the world, most of them working at so called "beamforming" questions. "Why didn`t they do their job? - Why we? - What have we done?" we asked us. Nobody of us had studied acoustics. We were newcomers in the field. Very slowly we realized, that we opened a new scentific field. So we proceed.

Pilot Version of the Amplifier

Michael Fritsch, FHTW Berlin-Karlshorst, FB3, developed in his diploma-thesis 1994 the prototype for the "high-freqency" (50 kHz), soft-controlled preamplifier for the WIN30-DS-card.




File created Jan. 12, 1996; revised: Jan. 15, 1996,
Adds 11/1997, 2/2023

Access no. since Sept. 10, 1996