Shielding noise

The pulser/receiver is completely shielded and therefore receives no noise coming from the PC components. The input connector is a Lemo 00 coupler. The extremely low noise amplifier with a maximum amplification of about 90 dB accommodates very small signals. A precise gain setting is possible up to 106 dB. 

If the temperature range of interest is large, say 1 to 400 K, then diode thermometers are recommended. Diodes have other advantages compared to resistance thermometers. By contrast, diode thermometers are veiy much smaller and faster. Bv selection of diodes all from the same melt, they may be made interchangeable. That is, one diode has the same cahbration cui ve as another, which is not always the case with either semiconductor or metallic-resistance thermometers. It is well known, however, that diode thermometers may rectify an ac field, and thus may impose a dc noise on the diode output. Adequate shielding is required. 

The philosophy of any EMI shield is to encourage eddy currents to flow within the surfaces, thus dissipating the noise energy. Also, the assembled enclosure should act as a gaussian enclosure where there is good electrical conduction totally around the enclosure. So removable hatches and enclosure members need very good electrical connections around their peripheries. RF gasketing is sometimes used in particularly troublesome cases. 

The siting, as well as the selection of type of tower, can be critical. Rotating the tower, shielding the motor, use of baffles can all help in meeting environmental noise requirements. If in doubt, consult your cooling tower designer. 

Every electronic system has some level of electromagnetic radiation associated with it. If this level is strong enough to cause other equipment to malfunction, the radiating device will be considered a noise source and usually be subjected to shielding regula-... 

The radiation detector is located some distance from the readout. A shielded coaxial cable transmits the detector output to the amplifier. The output signal of the detector may be as low as 0.01 volts. A total gain of 1000 is needed to increase this signal to 10 volts, which is a usable output pulse voltage. There is always a pickup of noise in the long cable run this noise can amount to 0.001 volts. 

Electronic noise. For a noise amplitude of 0.1 A only atoms separated by 4A can be resolved. Thus, the electronics must be carefully shielded, with the pre-amplifier stage placed as close to the tip as possible and the STM itself placed in a Faraday cage. 

Shields used to provide protection from intentional detonation of ammunition are to be designed to prevent exposure of operating personnel to impulse noise levels exceeding 140 decibels. 

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