Conex Club Magazine - no.3 - 2002

Conex Club Magazine - no. 3 - 2002 - Standards, errors and measurements

Reading time: 3 minute

The main topics presented

1. Clock signal structure - Technological design

In digital electronic products, the clock signal (also called tact signal or, more simply, CLK) is the one with the highest value of the frequency, in other words the signal that switches faster than any other signal in the respective system.

The clock interconnection structure is usually the most "loaded" because all circuits that require synchronization are connected to it.

In addition, it is known that the perturbations fall within the named field "electromagnetic interference" (crosstalk, reflections, electromagnetic emission / reception, disturbances through the power line or phase shift of signals) are more dangerous as the frequency increases, it is useful for any electronics technician, even an amateur, to know some technological aspects related to fast signal management. .

Those specified so far lead to the conclusion that the structure of the clock signal should not be considered trivial and that it is necessary to pay special attention to it in the wiring design phase and to carry out the practical assembly.

2. Gong with three tones

The "Gong with three tones" assembly is a simple construction, based on the integrated circuit SAE800 (Programmable Single / Dual / Triple Tone Gong) or SAB600 (Three-Tone / Dual-Tone / Single-Tone Chime). The most common application of this montage is music bell.

3. Disturbing signals in TV reception installations

The possible disturbing signals are analyzed as well as the way to remove them in the case of the radio-tv reception installation, type IRTVM, produced by EMIDIN O&O.

The multi-user radio-TV reception installation, type IRTVM, is used to amplify the radio-TV signals and distribute them on a network that feeds a certain number of subscribers.

The installation ensures the reception of radio programs with frequency modulation in the bands 64-74MHz and 88-108MHz, of VHF TV programs (channels 1-12), as well as of UHF TV programs (channels 21-69) by means of converters PLL / UHF / VHF.

The signals received by the various TV antennas are, as the case may be, amplified or converted from the tape UHF in the band VHF / Cable TV (50-300MHz), summed and then amplified in power to compensate for the attenuations introduced by the distribution elements.

4. Standards, errors and measurements

All fields of science are based on the interpretation of phenomena and on the attempt to experimentally model theories about the surrounding world.

Measuring some physical quantities is important and we try to evaluate them as accurately as possible.

The measurements we can make are of two types:

  • relative (direct) measurements;
  • absolute (indirect) measurements.

Direct measurements are those in which the size to be measured is compared directly with the standard, as happens for example when we measure the length of an object.

Indirect measurements are those obtained by processing data in a certain form, as is the case of sizes that involve the use of formulas.

Often a size can be measured by both methods; other sizes can only be obtained by indirect methods.

The fundamental quantities, on the basis of which a system of units of measurement is established, must be as few as possible in number, lead to the ease of calculating other quantities and must be specified by stable standards; the quantities that are deducted based on the fundamental ones are called derived quantities.

5. Milliohmeters

It is often necessary to measure small resistances, below 1 Ohm. Their measurement can also be performed with ordinary measuring instruments, analog or numerical. For example analog multimeter MF35 (MAV035) allows the measurement of resistances below 10 Ohms on the DW range.

The device described in the article is actually un adapter, powered by batteries, for a digital multimeter (DMM) which also has the field of 0… 0.2Vdc (0… 199.9mV) with input resistance greater than 1MOhm.

6. Portable programmer (E-Lab ICP-I)

Under this name E-Lab ICP-I is presented a mini-programmer for microcontrollers from the series AT90Sxxxx and ATmega128.

The connection with a computer is made on one of the serial ports (COM1, COM4) or optionally using the USB data port.

The possibility of reprogramming the circuits is unlimited. The programmer allows the loading of computer compiled files, in HEX format, and stored in internal memory.

The type of microcontroller you want to program, the lock bits, the oscillator type selection bits are chosen from the graphical interface on the computer monitor, the graphical interface delivered with the AVR miniprogrammer.

7. LM380 (Audio Power Amplifier)

LM380 is a power audio amplifier for consumer applications. To keep the cost of the chip at a low price, the gain is fixed internally at 34dB (50 times).

Both entrances have as common reference, the table. The output is centered internally at half the supply voltage (in the absence of any signal at the inputs).

8. 6m / 70cm Transverter

The construction is part of the series of very useful devices in the field of radiocommunications, for amateur radio traffic working in SSB mode.



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