Measuring the frequency of a signal may seem to be a simple process of counting pulses, but in order to get better accuracy, few other things should be considered, such as the gating interval and the range of measurement. This tutorial, posted on the pcbheaven.com, briefly describes two typical methods of frequency measurement: Direct Frequency Measuring (DFM) and the Reverse Frequency Measuring (RFM), with their pros and cons. [via]
A brief tutorial on frequency measurements - [Link]
This is 60 MHz frequency meter / counter for measuring frequency from 10 Hz to 60 MHz with 10 Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.
10Hz – 60MHz Frequency Meter / Counter – [Link]
This project is a frequency standard based on GPS signal that has the advantage of great stability.
Using the GPS Satellite system offers the advantage of very accurate timing and by extension, frequency control. The long term error is to all intents and purposes zero, with time and frequency accuracy being comparable to the international standard. The traditional route is to use a relatively low cost GPS receiver module which outputs a 1 Pulse per second signal (1 PPS) aligned to UTC.
GPS Disciplined Frequency Standard - [Link]
This project is a DIY power meter made by Bill Porter and it is used to monitor the electricity usage of his home. The device is able to measure the power the house is using, the power factor, voltage and frequency. The data is transmitted wireless to a display unit. View construction details, schematics and board on the link below. [via]
DIY power meter – [Link]
This project shows how to build a Spectrophotometer using a toilet paper roll, duct tape and a graphing calculator. Light is shined through a sample solution, passes through a diffraction grating, then shows up as bands of color on the projection surface. The photosensor can slide back and forth along the spectrum to get readings at different frequencies using a multimeter. [via]
DIY Spectrophotometer - [Link]
This tutorial shows how to use the Timer1 module inside PIC12F683 as an asynchronous counter to compute the frequency of an external clock source. The external clock is connected to the GP5/T1CKI port of PIC12F683 and the measured frequency value is sent to a PC through serial port to display on an hyperterminal window. A 555 Timer IC operating as an astable multivibrator is used as the external clock source. The Timer1 module is 16-bit so it can count up to 65535. If the Timer1 is turned ON for 1 sec, the maximum frequency it can measure is 65535 Hz. Any frequency higher than this will create Timer1 overflow. An interrupt service routine is also written to demonstrate how to detect the overflow and take appropriate action. This concept can be extended to measure higher range frequencies.
How to measure frequency of an external clock source using PIC - [Link]
This project reads the AC line frequency and displays on a LCD. The 120V AC is first converted to 12V AC using a step-down transformer. With the help of a BJT, the output Sine wave is further converted to 5V square pulses which is fed to TOCKI pin of PIC16F628A. The Timer0 module is used as an 8-bit counter. The counter counts the number of pulses arrived at TOCKI port in 1 sec, which, in fact, is frequency of manis AC, and displays it on a LCD.
Timer0 Counting AC Line Frequency - [Link]
Sylvain Bissonnette writes:
This is a simple project. The Frequency is passing through an op-amp to convert it in a square wave. The ouput of the op-amp is feeding the 3*8 bits counter (24 bits) who can accumulate at a maximum of 16777216 count. The maximum frequency you can measure without changing the time base of one second is 16.777216 Mhz. The ATMega8 have 3 functions: enable the counter gate at each second, read his value and display it on the LCD.
ATMega8 Frequency Meter – [Link]
In this project we are building a basic and low cost frequency counter circuit . It can measure from 16Hz to 100Hz signals with a maximum amplitude of 15V. The sensitivity is high, the resolution is 0.01Hz. The input signal can be a sine, a square or a triangle waveform.
Frequency Counter - [Link]
The device presented here can be used to count events as well as to measure frequencies and times. Most of it is built from discrete HC (high speed CMOS) logic and to be honest, if I needed to build such a device again, I would not build it as presented here but integrate things into a CPLD or a microcontroller instead. However, it was instructive not to do so and maybe it is interesting for other people as well (for what reason ever).
- Frequency measurement from 0.1Hz to ≥10MHz; gate times of 0.1, 1 and 10 seconds
- Time measurement 0.001ms to 10000s (time clock 1MHz and 1kHz): measuring L/H time or 1, 10 or 100 complete pulses or time between input A and B transition
- 5-digit LED display with display hold
- CMOS-compatible Schmitt-trigger inputs with over- and under-voltage protection
Frequency Counter - [Link]