Free Fresh Article: Capaci-Meter

With the compliments of the Elektor Labs and Editorial teams, here comes another fresh-out-of-the-lab article that's free to download by all registered Elektor e-zine readers. "Free Fresh Articles" are published at two-weekly intervals in the Elektor e-zine, alternating with "Free Back Articles". This time we have a DIY capacitance meter that’s remarkable for its accuracy, low cost and beautiful PCB design. It has a two-digit Dekatron-style display made from discrete LEDs, and zero (0) microcontrollers inside, yet achieves 5% accuracy across its range of 200 pF to 9.9 uF.

The Capaci-Meter is a capacitance meter with a retro-style ‘Dekatron’-type arrangement of LEDs to represent two digits. It is not designed to be an accurate measurement instrument. Instead it is aimed at establishing if a capacitor is close to the desired value, especially when it is difficult to read the values printed on the capacitor.

When performing measurements away from your electronics workbench, a portable instrument is exceedingly convenient, particularly if you have one that combines three measuring tasks. The JOY-iT DMSO2D72 offers the functionality of an oscilloscope, a multimeter and an arbitrary waveform generator in one convenient package. We had a go with it.

If (like most electronics buffs) you only have two hands with ten fingers on each, but lots of measurements to make on your boards, here is an interesting gadget for you. It’s the missing link between crocodile clip and contact point. It allows you to measure, continuously, hands free, with contact points without mechanical attachment, held in place by a flexible gooseneck arm. The probes are interchangeable and the support is very stable.

A new test of PCBite filmed by Roger, an Elektor reader who checks if this accessory lives up to its promises. Does it give reliable, hands-free measurements without mechanical linkage, held firmly in place by gooseneck arms? Do the befits of this accessory justify investing in it? The answer to these questions is set out in this video from Kainka Labs.

In the past, every electronics technician in his (hobby) lab had a function generator with an XR2206, but those days are long gone. Nowadays such a generator works with a DDS chip that generates frequencies digitally. Unfortunately, a decent DDS function generator isn't really cheap — or is it? The JOY-iT DDS function generator promises a wide frequency range and many possibilities at a low price.

Suppose you want to measure a slowly-varying voltage from a sensor, or perhaps plot the discharge curve of a battery. Is it really necessary to sit there and note down a reading from the multimeter every so many seconds or minutes? It is less tedious and much more elegant to use this Arduino-based unit connected to your oscilloscope. Two questions motivated Kurt Schuster at the beginning of this project: ‘is my battery any good?’ and ‘is this charger charging my battery correctly?’

All that’s required to measure radiation is a simple PIN photodiode and a suitable preamplifier circuit. We present here an optimised preamplifier and a microcontroller-based counter. The microcontroller takes care of measuring time and pulse rate, displaying the result in counts per minute.The device we describe can be used with different sensors to measure gamma and alpha radiation. It is particularly suitable for long-term measurements and for examining weakly radioactive samples.

It seems that to even dip your feet in the ocean of DSP (digital signal processing) you need lots of SMD soldering skills and a ton of math. Seems. Let’s end the anxiety: here is a Universal Audio DSP board for the DIYer. Based on the Analog Devices ADAU1701 DSP, this board has only through-hole components—except for the DSP itself.

To make accurate voltages measurements you need an A/D converter (ADC) chip which has good resolution. The folks at Elektor Labs have developed a board containing a four-channel 16-bit ADC. It’s no coincidence the board uses a Gnublin/EEC connector which makes it compatible with the Elektor’s Linux board, Xmega Webserver and the new Extension shield for Arduino. A universal C library is included to make integration a walk in the park.