Circuits & Schematics: frequency meter - 4

31. Make a truly linear RF-power detector
    Circuits Analogue Design Measurement Analog Devices AD633 AD707 AD8361
    .. signals over a wide dynamic range, but are not rms-responding. An alternative solution (Figure 1) uses the AD8361, a high-frequency true-power detector. Unlike the logarithmic amplifier, the AD8361 is an rms-to-dc converter and, ...
    .. output voltage that is proportional to the input power level in watts. You can easily adjust gain and offset for this power meter with an op-amp circuit, thus providing an output scaled in volts per watt. A complex RF waveform feeds the ...
    Sep 13, 2020

32. Measure inductance & capacitance over a wide range
    John Fattaruso
    Circuits Measurement Texas Instruments CD74HC14 LM78L05
    .. constant and the oscillation period. Figure 1. Basic scheme for measuring capacitors (a) and inductors (b) with variable frequency square waves. Now consider the complete schematic in Figure 2. A square wave is generated by IC1 wired ...
    .. the resulting voltage, averaged by C2 and C3, is measured by an external voltmeter. Figure 2. Complete schematic of C and L meter. Transients with an exponential decay that extend over a particular portion of the square wave period will ...
    Sep 20, 2021
33. Magnetic-Field Probe Requires Few Components
    Rama Sarma Sandeep Satav
    Circuits Measurement Allegro A1323
    .. troubleshooting moving-magnet linear-position detectors, fabrication of dc motors and audio speakers, investigation of low-frequency-magnetic-field interference, and designing and fabricating electromagnetic-interference shields. ...
    .. to feed a 5 V regulator IC, such as a 7805 voltmeter and add an on/off switch if desired. Place the batteries near the meter. Otherwise, the batteries' steel cases will disturb the magnetic field under observation. Use 10-nF SMD ...
    Jun 9, 2022
34. Inductor-Based Astable 555 Timer Circuit
    Arthur Edang
    Circuits Oscillators Texas Instruments LM555CN
    .. has become a default choice of many hobbyists and even professionals in the past 50 years. Its pair of equations for frequency and duty cycle easily gives capacitor-resistor combinations which satisfy the required output. But ...
    .. 51.96 3.17 Figure 2. R S of the inductor. To test these ideas, I picked the components listed in Table 2 and used an LCR meter to measure their actual characteristics (Figure 2). I plugged the values into the spreadsheet to predict T H , ...
    Oct 6, 2022
35. Zero-bias detector yields high sensitivity with nanopower consumption
    Mitchell Lee
    Circuits Wireless Analog Devices LTC1540
    .. yet have enough battery power in reserve to answer an incoming call. For smallest size, most operate in the ultrahigh frequency range, where the design of a micropower receiver circuit is problematic. Familiar techniques, such as ...
    .. proof-of-concept at 445 MHz. This circuit contains a couple of improvements over the standard L/C-with-whip field-strength meter. Tuned circuits aren’t easily constructed or controlled at UHF, so a transmission line is used to match ...
    May 23, 2023
36. 85V-260VAC to 5VDC-2.5A flyback switching power supply
    Hesam Moshiri
    Circuits Supply Dongke Semiconductor DK1203
    .. fuse and R1 is the 7D741 varistor to absorb high voltage transients. C2 is a 100 nF X2 rated capacitor to reduce the high-frequency noise and T1 is a common mode choke. BR1 is the Vishay MB6M bridge rectifier and C3 is a 22 ...
    .. a gap accurately and winding the transformer by hand and without any error is difficult. The easy solution is to use an LCR meter! first, wind the primary and assemble the transformer (without any gap). Then measure the inductance of the ...
    May 7, 2024
37. 85VAC-260VAC to 12V-0.5A AC-to-DC flyback converter using an RM6 ferrite core
    Hesam Moshiri
    Circuits Supply Dongke Semiconductor DK106
    .. is RM6 and DK106 is the controller chip. The inductance of the primary winding of the transformer is 2 mH and the switching frequency is 65 kHz. Output regulation is done through a Zener diode, and the controller chip does not need any ...
    .. Then put the ferrite cores in place (in the bobbin) and measure the inductance of the primary winding using an LCR meter. If you can set the measurement frequency on your LCR meter, the best frequency is 65 kHz (switching frequency ...
    Nov 17, 2025
38. 5-V ovens (some assembly required). Part 2
    Nick Cornford
    Circuits Supply Microchip MCP6002
    .. similar. At least this was designed from scratch. U1a forms a conventional oscillator running at around 1 kHz. Neither the frequency nor the exact wave-shape on C1 is critical. R1 and R2 + R3 determine the tri-wave’s offset, and ...
    .. of millivolts. (The fine copper wire used to connect the module to the outside world has a resistance of about 1 Ω per meter.) Q1 drops ~1.3 V and so provides about a third of the heating, rather like the corresponding device in Part 1. ...
    Apr 7, 2026
39. Dual-fan PWM cooling circuit with a 6W isolated flyback power supply
    Hesam Moshiri
    Circuits Supply Microcontrollers Usage Atmel ATtiny13
    .. In this circuit, the MOSFET is embedded in the controller. IC2 is the DK106 controller chip. The controller switching frequency is 65 kHz and operates with only a few passive components. It does not need a startup resistor and an ...
    .. Then install the ferrite cores in place (in the bobbin) and measure the inductance of the primary winding using an LCR meter. If you can select the measurement frequency on your LCR meter, the best frequency is 65 kHz (switching ...
    Jun 15, 2026
40. Painlessly convert Hz to 4-20mA current loop
    Stephen Woodward
    Circuits Supply Texas Instruments LM2917-N
    .. iconic LM2917 tackles frequency-to-current conversion with (very) few externals. Almost exactly 50 years ago in June 1976, to be ...
    .. flexibility makes them highly handy in other contexts, including industrial applications like monitoring turbine-type flow meter flow rate and small motor tachometry. Figure 1’s facile conversion of a frequency input to a universal ...
    Jul 16, 2026

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