Meters

This circuit, designed on request, has proven to be useful to indicate when the voltage in a power supply line is changing from 120V to 240Vac. It can be used in different circumstances and circuits, mainly when an increase in ac or dc supply voltage needs to be detected.

This simple circuit makes it posible to monitor the charging process to a higher level. Final adjustsments are simple and the only thing needed is a digital voltmeter for the necessary accuracy. Connect an input voltage of 12.65 volt between the positive and negative poles and adjust the 10K trimmer potentiometer until Led 10 lights up. Lower the voltage and in sequence all other Led's will light up. Check that Led 1 lights up at approximately 11.89 volts.

Having found an u664b prescaler chip (Telefunken) from an old tv-tuner , I decided to build a valid frequency counter using pic16f84 , the prescaler I use is able to divide by 64 every frequency from 30 to 1300 MHZ. The original project is from Peter Halicky but as he used a sab6456 prescaler (divider by 256)

This is a successor of the PIC16C71 4-digit LED f-counter & V-meter. Some hard to find parts used in the previous version, which are out of production for some time, has been omitted. A rather early PIC16C71 has also been replaced by 28-pin device PIC16F876. The later is capable of driving 4 digit LED display in multiplexed mode while measuring frequency, power supply voltage as well as handle two analog inputs to display SWR/PWR signal strength in a bargraph manner. There is no need for external LED display driver chip as well as external data EEPROM since it is already implemented in PIC16F876.

This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band. The SAB6456 is a prescaler for UHF/VHF tuners. The circuit has an input frequency range of 70 MHz to 1 GHz, has high input sensitivity and good harmonic suppression. With lower sensitivity it's usable down to 3 MHz. The circuit comprises an input amplifier, a divider stage and an output stage. The divider stage may oscillate during no-signal conditions but this oscillation is suppressed when input signals are received. The voltage-edges of the output signals are slowed internally to reduce harmonics in the television intermediate frequency band.

This application note describes a high accuracy, low cost 3-phase power meter based on the ADE7752. The meter is designed for use in a Wye-connected 3-phase, 4-wire distribution system. The ADE7752 may be designed into 3-phase meters for both 3-wire and 4-wire service. This reference design demonstrates the key features of an ADE7752 based meter, and is not intended for production.

At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become "dirty". If this happens too often or is too severe, tweeters are the first to go - they are damaged by the excessive power generated by a combination of "power compression" and the harmonics created when an amplifier clips.

Measures 10mV to 50Volt RMS in eight ranges. Simply connect to your Avo-meter set to 50µA range. Connect J2 and J3 to an Avo-meter set to 50µA range. Switching SW2 the four input ranges will be multiplied by 5. Total fsd ranges are: 10mV, 50mV, 100mV, 500mV, 1V, 5V, 10V, 50V. Set R11 to read 1V in the 1V range, with a sine wave input of 1V @ 1KHz. Compare the reading with that of another known precision Millivoltmeter or with an oscilloscope.

The Bray Barometer requires manual calibration for voltage offset and gain. Although practical on the workbench, these devices are most likely mounted in inconvenient locations making secondary adjustment difficult. The Bray Barometer uses potentiometers for offset and gain adjustments. Potentiometers are notoriously temperature sensitive, and sensitive to hostile environments.

This project is a simple tester for 1.25V rechargeable and 1.5V AA type batteries based on the LM3914 chip and a LED line. The electrical schematics is shown on figure. The heart of this device is the LM3914 integrated circuit manufactured by National Semiconductor. This chip is a simple A/D converter built of a chain of comparators. In this application the IC works in it's typical configuration. The comparator outputs are connected directly to LEDs.