Showing posts with label meter. Show all posts
Showing posts with label meter. Show all posts
Sunday, November 16, 2014
Digital Volt Meter Circuit
Digital volt meter circuit is simple and not much use of additional components. Volt meter circuit uses IC L7107 as a main actor. L7107 IC is an Analog to Digital Converter (ADC) which has been equipped with the viewer seven segment driver 3 1 / 2 digits. IC L7107 in the application of digital volt meter is in it has been equipped with an internal voltage reference circuit, analog switches, sequential control logic, and LED display driver. This digital meter volt circuit can be operated with a working voltage 5VDC. A full suite of digital volt meter can be seen in the following figure.
To set or Calibration to 0 Volt. done by adjusting the VR 2KOhm. then to test the display can be done by pressing the test switch, where to normal conditions when the switch is pressed then all the display lights up.
Thursday, September 4, 2014
Stereo Circuit Balance Meter
Description
When L R signals are equal, no output is present from Ul, and pin 6 is at a steady 4.5 V. Unbalanced audio causes the LEDs to vary in brightness,which causes a difference that corresponds to unbalance between channels.Circuit Diagram
Tuesday, August 12, 2014
PC based Frequency Meter
Here is a simple technique for measuring frequencies over quite a wide frequency range and with acceptable accuracy limits using a PC. It follows the basic technique of measuring low frequencies, i.e. at low frequency, period is measured for a complete wave and frequency is calculated from the measured time-period.
Cascaded binary counters are used for converting the high-frequency signals into low-frequency signals. The parallel port of a computer is used for data input from binary counters. This data is used for measuring time and calculating the frequency of the signal. The block diagram shows the basic connections of the counters and parallel port pin numbers on 25-pin ‘D’ connector of a PC (control register 379 Hex is used for input). External hardware is used only for converting the higher frequency signals into low frequency signals. Thus, the major role in frequency-measurement is played by the software. The PC generates a time-interrupt at a frequency of 18.21 Hz, i.e. after every 54.92 millisecond. Software uses this time-interrupt as a time-reference. The control register of the PC’s parallel port is read and the data is stored continuously in an array for approximately 54.9 ms using a loop. This stored data is then analysed bit-wise. Initially, the higher-order bit (MSB or the seventh-bit) of every array element is scanned for the presence of a complete square wave. If it is found, its time period is measured and if not then the second-highest order bit (sixth bit) is scanned. This operation is performed till the third bit and if no full square wave is still found, an error message is generated which indicates that either there is an error in reading or the frequency signal is lower than 19 Hz. Lower three bits of the control register are not used. When a wave is found, along with its time-period and frequency components, its measurement precision in percentage is also calculated and displayed. Number of data taken in 54.9 ms is also displayed. As stated above, the lower starting range is about 19 Hz. Data is read for approximately 54.9 ms. Thus, the lowest possible frequency that can be measured is 1/.0549 Hz. Lower range depends only on the sampling time and is practically fixed at 19 Hz (18.2 Hz, to be precise). Upper range depends on factors such as value of the MOD counter used and the operating frequency range of the counter IC. If MOD-N counter is used (where N is an integer), upper limit (UL) of frequency is given by UL=19xN5 Hz. Thus for MOD 16 counters UL@20 MHz, and for MOD 10 counters UL@1.9 MHz. Care should be taken to ensure that this upper limit is within the operating frequency range of counter IC used. Precision of measurement is a machine-dependent parameter. High-speed machines will have better precision compared to others. Basically, precision depends directly upon the number of data read in a standard time. Precision of measurement varies inversely as the value of MOD counter used. Precision is high when MOD 10 counters are used in place of MOD 16 counters, but this will restrict the upper limit of frequency measurement and vice-versa.
Sunday, August 10, 2014
Audio Notch Meter
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