Measurement Circuits


Track Your Distance Through a Bicycle Odometer

Just like cars that measures the distance it can travel, you can also do it with your bicycles. We usually keep track of our mileage to see how far our strength can go but would it be of great use if we track it because we are maintaining a workout everyday considering the calories we […]


Cheap AC Current Measurement

The easy way to measure high AC currents is to use a clamp meter but these are generally quite expensive and cost several hundred dollars at a minimum. Add-on clampmeter adaptors can work well but they only work with digital multimeters which have millivolt AC resolution. This is because the output of most clamp adaptors […]


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 […]


Check Inductors With This Simple Q Meter

While LCR meters are readily available at reasonable cost, they do not measure the Q of an inductor. This circuit enables you to measure the Q of inductors with the aid of an RF signal generator. A capacitor is connected in parallel with the inductor to form a tuned circuit. By varying the frequency, you […]


Digital Bike Tachometer

This digital DIY tachometer for bikes uses two reed switches to get the speed information of the bicycle. The reed switches are installed near the rim of the wheel where permanent magnets pass by. The permanent magnets are attached to the wheelspokes and activate the reed switches everytime they pass by it. The speed is […]


Multimeter as Lightning Detector

Most digital multimeters have a sensitivity of 200 mV and in input impedance of 10 MR. With this information you can calculate that at full scale there will be a current of 20 nA (nano-ampères). In reality you have a very sensitive ammeter in your hand. Now that we know this, it becomes a mission […]


Speedometer For Model Cars

Avid model car fans are naturally enough always interested in the technology and performance of their cars. They would like to know as exactly as possible how fast their model cars actually go, for example so that they can select the final gear ratio for the best performance. Other factors can also be of interest, […]


Audio Power Meter

This simple circuit indicates the amount of power that goes to a loudspeaker. The dual-color LED shows green at an applied power level of about 1 watt. At 1.5 watts it glows orange and above 3 watts it is bright red. The circuit is connected in parallel with the loudspeaker connections and is powered from […]


Photo Meter Assesses Ambient Light

Most PN-junction diodes can be used as photodiodes. While not optimized for this application, they do work. When the diode is reverse biased, it will produce a small photovoltaic output as the light level is increased. LEDs are particularly suited for this task because their housings are transparent.You can construct a simple circuit that will […]


Meter Adaptor With Symmetrical Input

In contrast to an ordinary voltmeter, the input of an oscilloscope generally has one side (GND) connected to ground via the mains lead. In certain situations this can be very problematic. When the measuring probe is connected to a circuit that is also connected to ground, there is a chance that a short is introduced […]