Schematics for this Siemens instrument

Dear Follow members,

I have this interesting "light writer" from Siemens. There is no type name on it. On the cover lid it is written A2=72 V.

Inside:

- 3 Telefunken valves

- a clockwork

- a film holder

Anybody has any idea about it?

Attached some picture:

• 1_Siemens A2-72V (220 KB)
• 2_Siemens A2-72V (225 KB)
• 3_Siemens A2-72V (204 KB)
• 4_Siemens A2-72V (256 KB)

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Hi Francisc,

this unit is for registration of electrocardiograms on (35mm?) film.

Here the electrodes are connected to both arms and one leg.

Picture 4 (underside) shows the film spools on the right.

See electrocardiography.

Best Regards,

Georg

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Yes, there is inside a piece of 35 mm film! The device it luks more industrial than medical. Than the inscription A2=72V it means that a specific electrode has 72V? At first, I was thinking that A2=72V it is the type name.

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Francisc,

the electrodes are "pick ups" for the heart signals of the human body which are about plus/minus 0,5 Millivolt.

This signal is affected by the offset voltage of the electrodes, depending of the material plus/minus 300 Millivolt (or so). The amplifier can eliminate this offset voltage by a bias voltage of opposit polarity than the offset.

The signal is also affected by the environmental AC hum or high frequent signals or pulses which has to be filtered or eliminated.

The unit in question has three signal inputs of very high impedance, because the source impedance of the human body and his skin is of certain high impedance.

Folllowing that, 72V sent to the electrodes makes no sense at all. AC50V can be mortal, DC120V is also harzardous. 72V is not very "comfortable" for the body. I don't see "72V" - where it is mentioned?

All the knobs and elements on the front are numbered according to "Bedienungsanleitung" (instruction badge), see below. The three electrodes are missiing?

Please try to evaluate the circuit diagram - it seems not so complicated as three stages might be identilcal (more or less).

Please check parts inside for date codes.

Best Regards

Georg

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It is written on the wiht label inside the cover (see picture 1).

You are right this is a medical equipment from 1930!!! Thank you for the translation.

I found a picture on "Medical College of Wisconsin", MCW Libraries Digital collections, Siemens Electrocardiograph, but I can not ad the link!

The schematic for it would be intersenting!

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Francisc,

try to suggest as new model.

Manufacturer: Siemens; D S.& Halske / S. Electrogeräte

Model name: ElektroKardiograph

Type: as "A2=72 V" is obscure - leave it blank meanwhile.

Year: 1930 (but verify with date codes on parts!)

Add the tube layout

Power supply: AC

Line voltage: (check the transformer - if nothing mentioned leave it blank)

I will send you german text for "remarks" soon.

If the model is accepted by the admins (good luck!) you can activate "I search the schematic". If the schematic or an other document will be uploaded you will get an automatic email.

Best regards,

Georg

Here is the link to the Medical College of Wisconsin.

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I’ve checked out the valves line up: RE034, RE034 and RE 134. All are in good condition.

Mean while the manufacturing year is 1938 as stated on the capacitors!

I start to make the schematics… hope to succeed!

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Guten Tag,

In Schritt zwei sollen "die Spannungen" geprüft werden, dabei gibt es am Wahlschalter A1 und A2. Für mich liegt nahe, dass A2 auf das Vorhandensein von 72V geprüft werden soll - sicher eher eine Anodenspannung als irgendetwas, das in die Nähe der Elektroden kommen sollte.

Ein Schaltplan wäre sicherlich interesant.

MfG

Stefan Hübner

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Here is the link ...

Enjoy,

Feri

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 I asked for a new model... but no answer yet!

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Meanwhile the model is here - but the text in the remarks "Possible use outside medical context as a general signal recorder" is just fantasy:

As it is a German model, the text will be reviised in german langauge, describing the  real purpose only.

Best Regards,

GR

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Thank you for all you have done to document this model. Of curse, I do not intend to change the initial designation of the electrocardiograph. I just was wondering about the principle which is used in other instruments too.

According to the logo type, the company name should  be Siemens-Reiniger which was busy with medical engineering.

Regards

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