Simple Phase Shift Meter for Audio Frequency Signal

Simple phase shift measurement can be done by squaring both the measured and the reference, then compute the difference of the two signals. The accuracy of the circuit shown in the schematic diagram  below is 1% UP to 2000 cps.

This circuit is used in computers and for high speed analog instrumentation. Negative value for zero phase shift is indicated by the zero center DC ammeter, zero for 90′ phase shift and some maximum value for 180′ phase shift.

 Phase-Shift Meter for Audio Frequency Signal Circuit Diagram

Read More

Simple Stereo VU Meter

I like to see lights move to music. This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier. You want to build two identical units to indicate both right and left channels. The input signal level is adjusted by the 10k ohm VR. If you wish to make a very large scale model of this unit and hang it on your wall there is an optional output transistor that can drive many LEDS at once. The unit I built drove three LEDS for each output. The sequence of the LEDS lighting are as follows Pin 1, 18, 17, 16, 15, 14, 13, 12, 11, 10.

Streampowers

Read More

ESR Low Resistance Test Meter

As electrolytic capacitors age, their internal resistance, also known as "equivalent series resistance" (ESR), gradually increases. This can eventually lead to equipment failure. Using this design, you can measure the ESR of suspect capacitors as well as other small resistances. Basically, the circuit generates a low-voltage 100kHz test signal, which is applied to the capacitor via a pair of probes. An op amp then amplifies the voltage dropped across the capacitor’s series resistance and this can be displayed on a standard multimeter. In more detail, inverter IC1d is configured as a 200kHz oscillator.

Its output drives a 4027 J-K flipflop, which divides the oscillator signal in half to ensure an equal mark/space ratio. Two elements of a 4066 quad bilateral switch (IC3c & IC3d) are alternately switched on by the complementary outputs of the J-K flipflop. One switch input (pin 11) is connected to +5V, whereas the other (pin 8) is connected to -5V. The outputs (pins 9 & 10) of these two switches are connected together, with the result being a ±5V 100kHz square wave. Series resistance is included to current-limit the signal before it is applied to the capacitor under test via a pair of test probes. Diodes D1 and D2 limit the signal swing and protect the 4066 outputs in case the capacitor is charged.

Circuit diagram:

 ESR & Low Resistance Test Meter Circuit Diagram

A second pair of leads sense the signal developed across the probe tips. Once again, the signal is limited by diodes (D3 & D4) before begin applied to the remaining two inputs of the 4066 switch (pins 2 & 3 of IC3a & IC3b). These switches direct alternate half cycles to two 1μF capacitors, removing most of the AC component of the signal and providing a simple "sample and hold" mechanism. The 1μF capacitors charge to a DC level that is proportional to the test capacitor’s ESR. This is differentially amplified by op amp IC4 so that it can be displayed on a digital multimeter – 10Ω will be represented by 100mV, 1Ω by 10mV, etc. To calibrate the circuit, first adjust VR1 to obtain 100kHz at TP3.

Next, momentarily short the test probes together and adjust VR4 for 0mV at pin 6 of IC4. That done, set your meter to read milliamps and connect it between TP4 and the negative (-) DMM output. Apply -5V to TP2 and note the current flow, which should be around 2.1mA. Transfer the -5V from TP2 to TP1 and adjust VR2 until the same current (ignore sign) is obtained. Remove the -5V from TP1. Again, set to your meter to read volts and connect it to the DMM outputs. Apply the probes to a 10W resistor and adjust VR3 for a reading of 100mV. Finally, ensure that all capacitors to be tested are always fully discharged before connecting the probes.

Author: Len Cox - Copyright: Silicon Chip Electronics

Read More

SWR Meter

At transmission channel that is not match besides incident wave flows also reflected wave. The direction is incident wave from source of to burden (from transmitter to antenna), while reflected wave from direction that is on the contrary (from antenna towards to transmitter). To measure the wave power is required by Power Meter. Usually at Power Meter there are two scales, firstly applied for power to come and other for reflects power. Level of scale is for reflect power smaller than coming power scale.

SWR METER (Standing Wave Ratio Meter - standing wave comparison meter) applied to measure comparison of incident wave and reflected wave. Equally SWR METER applied to measure how to match a source with burden. Job (activity principle SWR Meter constituted at Power Meter. if at one particular measurement only there is Power Meter hence countable SWR from power comes and reflects power.

Read More