Meters

This is 7-digit frequency meter measuring frequency from 10 Hz up to 1300 MHz. It is based on ideas of PIC16F84 based frequency meter. The measuring range is divided into two subranges: 10Hz - 25MHz and 25 MHz - 1300MHz. The decimal point is after MHz digit, but can be set at any position.

The circuit does not present particular difficulties for somebody that has a small experience. The two circuits are the himself, with a small difference only in their input, when they have they measure voltage or current and in connection that concern decimal point [ dp ]. In the department of input IC1 and IC3, exist the CA3161E, that is a A/D Converter for 3-Digit Display. In the drive of Display IC2 and IC4, exist CA3161E, that is a BCD the Seven Segment Decoder/ Driver.

This is a successor of the PIC16C71 4-digit LED f-counter & V-meter. Some hard to find parts used in the previous version, which are out of production for some time, has been omitted. A rather early PIC16C71 has also been replaced by 28-pin device PIC16F876. The later is capable of driving 4 digit LED display in multiplexed mode while measuring frequency, power supply voltage as well as handle two analog inputs to display SWR/PWR signal strength in a bargraph manner. There is no need for external LED display driver chip as well as external data EEPROM since it is already implemented in PIC16F876.

This application note describes a high accuracy, low cost 3-phase power meter based on the ADE7752. The meter is designed for use in a Wye-connected 3-phase, 4-wire distribution system. The ADE7752 may be designed into 3-phase meters for both 3-wire and 4-wire service. This reference design demonstrates the key features of an ADE7752 based meter, and is not intended for production.

A bit-error-rate (BER) tester is a basic tool for digital-communications measurements. Although many commercial BER testers are available, you can easily design and build an inexpensive version. The scheme in Figure 1 has performance similar to that of a commercial tester but requires you to perform a manual calculation based on displayed data. The tester displays received bits and received erroneous bits, and you must calculate the BER data using a handheld calculator, for example.

The Femto Capacitance Meter measures in the low femtofarad area having a resolution of 10 femtofarads (fF). The meter has six ranges allowing a maximum measuremenet is 4 microfarads. This allows one picofarad to be measured with 1% error. The need for this is in the fact that the best meters by previous designs would have 20-50% error on 1pF. This precision requires elimination of test leads. Instead insertion pins are used. Since capacitors are not measured in-circuit, there are advantages in removing test leads which create clutter.

This is a very straightforward circuit. The first stage acts as a crystal receiver. Use a germanium detector diode (like 1N34, but AA119 is much more common in Europe), a silicon one won't do. The frequency is determined by L and C. For the FM band and VHF, wind a coil 5mm in diameter, 6-8 turns of coated wire 1mm thick. You can always vary the frequency by spacing the turns a bit looser or tighter. C is much less critical. Something around 100p is preferable, though.

This Field Strength Meter is simple and also quite sensitive. It uses an ordinary digital voltmeter to measure RF signal strength up to a few hundred MHz. The multimeter should be set to the lowest dc volts range for maximum sensitivity. This is normally 200mV DC for most meters. The circuit works well at VHF (around 100MHz) and was quite pleased with the results. L1 was 7 turns on a quarter inch former with ferrite slug.

An [...] idea is to use the 555 as a monostable, and trigger it with a fixed frequency clock. Duty cycle will be proportional to capacitance. The ON time for the monostable is about 1.1RC, so component values that should work would be a 50 Hz clock, say a 1 Hz low-pass filter on the output, and R = 9.09K, 1%. That combination will give an output of one volt per microfarad. Switch R in decades for smaller capacitors. Trim R for calibration.

This is a wide band signal strength meter circuit which responds to small changes in RF energy, designed to be used for the VHF spectrum and will respond to AM or FM modulation or just a plain carrier wave. This circuit measures radio field strength by converting the signal to DC and amplifying it. This field strength meter was designed for VHF frequencies in the range 80 -110 MHz.The inductor L1 is 4 to 6 turns of 20swg wire air spaced wound on a quarter inch former or similar.

Battery-powered digital hour meters commonly monitor how long a machine is in operation by detecting when the machine is supplied with power. However, it is often difficult or dangerous to connect a battery-powered hour meter to a line-powered machine. When the machine being monitored produces de-tectable vibrations, you can use the circuit in Figure 1, which doesn't require any power-line connections.

To build the filter module we first need to understand the schematic. The schematic acts like a set of instructions. It gives you a list of parts and instructions on how to connect them. What makes this schematic more difficult to read is that some of the parts are interconnected on modules. You will need to compare the schematics of the individual modules with the overall schematic.

With a few inexpensive ICs and passive components, you can easily make a multirange power meter suitable for use on your benchtop. The circuit in Figure 1 measures currents from microamps to amps and voltages as high as 100V. The voltage at VOUT, which you can monitor with a DVM, indicates the load's power. Two 9V batteries can run the circuit (±V=±9V), which has a current drain of 10 mA.

Using a modern multimeter to measure current can sometimes be difficult. Many of these meters will only measure up to one amp. However, may 112-volt DC powered projects draw a lot more than that. If you have ever thought of purchasing a commercial shunt to solve the problem, your know just how expensive they can be. Commercial shunts, while very precise, frequently cost more than the projects they are measuring!

You can use a multimeter with capacitance-measurement capability to measure the length of wire or cable to an open circuit. The capacitance of a pair of wires (or a wire to a shield) is directly proportional to the length of the wire. If you know the capacitance per foot of wire, then you can calculate how far it is to the open circuit.

Large moving-coil meters may require significant amounts of current for full-scale deflection, and using a shunt resistor may prove impractical when the meter current is larger than the current you are measuring. You can solve the problem by driving the meter from a separate power supply (Figure 1). In this example, an 8-in. moving-coil meter that requires 15 mA for full-scale deflection displays a current range of 0 to 1A dc. This technique can also simplify specifying or fabricating shunt resistors for custom current ranges.

This device is for monitoring the rate of flow of powder used in a rapid prototyping machine. The sensor and LED are mounted about 2.5 inches apart. The sensor and LED have working apertures of about a quarter inch. The powder stream is one or two millimeters across. The first major problem is that only a small fraction of the sensor aperture is actually used so the maximum signal is only a small fraction of the zero opacity signal. Also, the actual opacity of the powder stream is not great.

Using minimum component count; this simple circuit will indicate peak audio response on an analogue meter, similar to a tape recorders meter. The circuit uses an opamp as a non inverting amplifier, but with one addition - a diode in the feedback loop. The circuit has a fast response time and slow decay time to indicate peak readings. The 1N4148 diode provides half wave rectification of the input signal, the dc output being smoothed by the 22u capacitor.

You need phase measurements to set up and verify electronic devices in amplifiers and in audio, control, ultrasound, and echo systems. Phase measurements can be problematic, because not many simple, inexpensive phase meters are available. Moreover, using an oscilloscope is time-consuming and imprecise. The phase meter described here uses a standard voltmeter as an output device. It measures the phase difference between two signals with better than 1% accuracy and it operates to 10 MHz.

This circuit uses a CA3420 BiMOS op amp to form a picoammeter with 4 ranges. The exceptionally low input current (typically 0.2pA) makes the CA3420 highly suited for use in a picoammeter circuit. Input transient protection is provided by the 1 megohm resistor in series with the input. The 10 megohm resistor connected to pin 2 decouples the potentially high input capacitance often associated with lower current circuits and reduces the tendency for the circuit to oscillate under these conditions. The 10k potentiometer is used for null offset.