DE1238564B - OE damping for fast oscillating galvanometers - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY Int. Cl .:

GOIr -1/14

GERMAN

PATENT OFFICE

PATENT LETTERING

German class: 2Ie-1/14

Number:

File number:

Registration date:

Display day:

Issue date:

P 12 38 564.7-35 (S 85681)

June 14, 1963

April 13, 1967

May 13, 1971

The patent specification differs from the patent specification

The invention relates to oil damping for mirror galvanometers designed as coil oscillators with an oil filling standing in a tubular body, which includes the oscillating system of the mirror surrounds.

Such mirror galvanometers are known from US Pat. No. 2,596,019. The subject of this However, the patent also relates to a galvanometer, the mirror of which is not in the oil filling immersed, but is separated from this by means of a barrier liquid. The barrier fluid is intended to prevent the damping oil from entering the housing part occupied by the mirror.

Fast oscillating galvanometers, so-called loop or coil oscillators, are used for imaging of rapidly changing electrical processes along a time axis on a recording. strip. The processes shown are only reproduced exactly if the oscillator is properly damped and its natural frequency is considerably higher than the frequency of the process to be registered. Electromagnetic damping is sufficient if the vibrator's natural frequencies are greater than 500 Hz is no longer off, and the oscillator must also be mechanically damped. This happens with the Coil oscillators, which are exclusively considered in the following, usually by an oil pipe damping. A tube encloses a part of the movable organ and is filled with a liquid whose Toughness is adapted to the desired limit frequency of the oscillator. The oscillating mirror will in these known galvanometers not covered by the oil. As a liquid are synthetic and Mineral oils used. However, the viscosity of mineral oils is strongly dependent on the temperature, so that the attenuation and thus the reproduction properties of the galvanometer also depend on the Be temperature dependent. Synthetic oils, for example, show better temperature behavior Silicone oil.

However, in the case of rapidly oscillating galvanometers, in particular the coil oscillators mentioned, those with synthetic tubes partially encompassing the moving system standing oils are dampened, at higher cut-off frequencies anomalies, which the dimensionally accurate Very badly affect the mapping of rapidly changing processes. When registering, for example of a rectangular jump there is a strong undershoot in the rising edge before the final amplitude is reached to observe from which the oscillating system exponentially reaches its end position oil damping for fast oscillating galvanometers

Patented for:

Siemens Aktiengesellschaft,

Berlin and Munich,

8000 Munich 2, Wittelsbachcrplatz 2

Named as inventor:

Dipl.-Ing. Paul-Ferd. Müller, 7500 Karlsruhe

approaching. In the case of a normal transient process with a degree of damping of α = 0.7, on the other hand, the overshoot occurring on the rising edge 4.3% of the total deflection. An undershoot that usually follows is hardly noticeable. The abnormal damping behavior of fast-oscillating galvanometers dampened with a synthetic oil is shown also in the amplitude frequency response of the galvanometer. After that, the amplitude falls in a frequency range from about 30 to 60% of the natural frequency of the oscillator not damped with oil. Electrically damped oscillators, i.e. those without oil damping, produce sinusoidal ones in this frequency range Measured variables error-free again. The observed decrease in amplitude in the range mentioned This is then followed by an increase in resonance.

To the mentioned anomalies in the damping behavior of fast-oscillating coil oscillators eliminate, for their oil damping with an oil filling standing in a pipe body, which the surrounding oscillating system including the mirror, provided according to the invention that with rapidly oscillating Galvanometers using the design parameters that are not related to the attenuation Measure additional contact or displacement surfaces for the damping oil on the vibrating System are arranged and thereby the oil filling from a synthetic oil with a viscosity consists of damping the rapidly oscillating galvanometer without the aforementioned additional Space alone is not enough.

In contrast, in the case of the known high-frequency coil oscillators, the damping was mainly by increasing the viscosity of the

10 * 00/3 * «'

fung oil has been discontinued. This damping element is located in known oscillators in a tube, which is part of the moving system, is not however surrounds the oscillating mirror.

When the rapidly oscillating galvanometer according to the invention is used to improve the damping The viscosity of the synthetic damping oil is no longer increased. Rather, the viscosity remains on set a value that corresponds to an attenuation of the galvanometer at a medium frequency, for example K) (K) Hz. Another increase that becomes necessary when the frequency increases the attenuation is in the galvanometer according to the invention by an increase in the effective Contact or displacement surfaces between the moving system and the damping oil achieved.

The invention is based on the knowledge that with increasing frequency the anomalous elastic Properties of synthetic oils in particular increase significantly. This results in an increase in the resetting elastic torque of the oscillating system, thereby increasing the resonance frequency can rise above the natural frequency of the undamped measuring mechanism. In contrast, the dynamic The viscosity of the synthetic oil increases with the frequency of the oscillator that shears the oil claimed from.

To increase the damping, high-speed vibrations dampened with synthetic oil are used Galvanometers do not set the viscosity above a certain value because they are more viscous synthetic oils in contrast to the behavior of normal mineral oils and low-viscosity synthetic oils Oils the elastic properties of the oil increase very sharply under shear stress. Λη Instead of a higher-viscosity oil, a low-viscosity oil is therefore selected and the effective one Increased damping area between the oscillating system and the oil.

The invention is explained in more detail using an exemplary embodiment shown in a figure. The figure shows a longitudinal section through a high-frequency coil oscillator. A housing 1 that . '. Is carried out oil-tight, has an oil-tight screwed optical lens 2 on the front, through which a Light beam falls on an oscillating mirror 3 and thrown back from there through the same lens will. The oscillating mirror 3 is on one

ίο voice coil 4 attached, located in the air gap between can rotate two pole pieces. One of the pole shoes 5 can be seen in the sectional drawing. On tlen pole pieces there is a recess 6 to allow space in the relatively narrow air gap

is for the movement tics mirror to create. the Voice coil 4 is attached to two tensioning straps 7 and 8, which in turn are mounted on a frame 9 are. The oil-tight housing 1, in which the frame 9 is inserted, a screw IO after assembly with the damping oil is at least as high Well filled, let mirror 3 also be surrounded by oil is.

Claims (1)

Claim: Oil damping for mirror galvanometers designed as coil oscillators with one in one Pipe body standing oil filling that surrounds the vibrating system including the mirror, characterized in that with rapidly oscillating galvanometers over the non-attenuation-related design parameters resulting in additional dimensions Contact or displacement surfaces for the damping oil are arranged on the vibrating system and the oil filling consists of a synthetic oil with a viscosity suitable for Damping of the rapidly oscillating galvanometer without the aforementioned additional 4 <> Areas alone are not enough. 1 sheet of drawings