Meters

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Many beginners trying out their skill with QRP TX, for the first time have to overcome many problems before they are able to come on the air. On usual complaint is that, every thing is working fine but the signal is not going out. Here is a simple set up which will enable them to measure the out put power of their transmitter. All that they require is a good multimeter which has a sensitivety of 20k ohms/4 Watts which is adequate for low power transmitters. The 8k resistor should be kept close to the out put terminal of the transmitter...

When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane. I did not have access to a milliohmmeter or an equivalent tester for locating this type of short circuit. So, I logged onto the Internet to find an easily constructible milliohmmeter. I found the answer in a manufacturer`s data sheet, which outlined the basic four-wire method of making low-resistance measurements...

A project posed the challenge of replacing existing analog potentiometers (used to set brightness and contrast levels) in video monitors with digitally controlled potentiometers. The different brands and models of monitors presented widely varying voltages across the potentiometers...

This nifty sound level meter is a perfect one chip replacement for the standard analog meters. It is completely solid state and will never wear out. The whole circuit is based on the LM3915 audio level IC and uses only a few external components. This circuit can also be integrated into audio amp projects...

From a high-volume-production point of view of the Design Idea `Test batteries without a voltmeter` (EDN, Nov 9, 2000, pg 167), it is a time-consuming and laborious task to tweak the large number of potentiometers on each of the comparator input references. An alternative to this onerous adjustment chore is to replace all potentiometers with 1%-tolerance fixed resistors (Figure 1). Before calculating each voltage-reference resistance value, you should use a reasonable selected total resistance value, RTOT, ranging from 100 k to 1 M...

This circuit is from Tomi Engdahl's page. It describes a nifty little TDR that, when combined with a regular oscilloscope, can be used to find discontinuities on long runs of cables...

A previously published Design Idea (Reference 1) uses a heated transistor as an airspeed-to-frequency converter. Because it uses only one transistor, the circuit cannot determine the direction of airflow. Alternatively, a circuit that uses a trio of hot transistors can digitize both wind speed and direction (Figure 1)...

With a few inexpensive components and INT1Ch, you can turn the printer port of your PC into a high-current ammeter. This design`s goal is to make remote high-current measurements, but you can use this technique to remotely measure any other similar analog electrical quantity, such as voltage and charge, at moderate speeds without going for expensive, PC-based general-purpose or tailor-made data-logging add-on cards...

VU (Volume Unit) meters used to be the mainstay of audio metering systems, but they have been replaced by LED metering in a great many mixers and other applications. Even in software, the most common level meter is made to look like an LED meter. The Peak Programme Meter (PPM) was originally developed by the BBC to overcome the shortcomings of the VU meter, which is notoriously bad at showing the peak signal level. The VU meter is average reading, and the ballistics are important if an accurate reading is to be obtained...