Meters Circuits

The 2N5457 and PN2222 bipolar serve as voltage isolation devices between the output and the current sensing resistor, Rl. The LM101 provides a large amount of loop gain to assure that the circuit acts as a current source..

Precision current sink

The 2N5457 JFET and PN2222 bipolar have inherently high output impedance. Using Rl as a current sensing resistor to provide feedback to the LM101 op amp provides a large amount of loop gain for negative feedback to enhance the true current sink nature of this circuit..

Ten-step voltage-level indicator

This ten-step adjustable analog level detector is capable Of sinking up to 40 milliam-peres at each output. The voltage range at the input pin should range from 0 to 2 volts. Circuits of this type are useful as liquid-level indicators, pressure indicators, and temperature indicators..

Current Source For Resistance Measurements Circuit

Useful for low-resistance measurements, this 1-A current source will produce 1 A in unknown resistance Rx. For best results, R,c should be less than 1 to 2, because only 3 V are available...

Simple continuity tester

The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a multivibrator, the frequency of which is influenced by the resistance between the test points. ..

Light meter

This light meter has an eight-decade range..

Ground-earth tester

The circuit is simple and foolproof if wired correctly. Under normal conditions, only lamps 1 and 3 should be lit...

Current source

This precision current source has 10 ÂµA to 10 mA ranges with output compliance of 30 V to -5V. Output current is fully adjustable on each range with a calibrated, ten-turn potentiometer..

Duty-Cycle Measurer

An Intersil 7101 31/2-digit A/D converter is used to display the duty cycle of a pulse train as a percentage. The frequ..

Nano ammeter

The complete meter amplifier is a differential current-to-voltage converter with input protection, zeroing and full scale adjust provisions..

B-Field Measurer

This circuit develops an output voltage that is proportional to the magnetic induction, B, flowing through its probe"s coi..

Digital Altimeter Circuit

A pressure sensor (IC4) is used with a dc: amplifier to convert the bridge output (IC4) to a single-ended voltage. ICld provides a reference voltage for setting barometric pressure. IC3 is an A/D converter manufactured by Intersil. This drives an LCD module. Calibration reads out in fact...

Smeter

This design is for an external signal strength meter that is analog, digital, and audible for mobile transmitter hunters. The S meter also incorporates a gain circuit. The digital LED bar graph display has a very fast response time. The 3.3-KO resistor near LM3914 can be replaced with a 5-K pot to control LED brightness. The S2A position gives a 2:1 gain and the S2B position gives about a 50:1 gain. The calibration pots control the amount of meter action relative to.....

Track-and-hold

The 5-MHz track and hold shown here has a 400-kHz power bandwidth driving Â±10 V. A buffered input follower drives the hold capacitor, C4, through Ql, a low resistance FET switch. The positive hold conuuand is supplied by TTL logic, with Q3Ievel shifting to the switch driver, Q2. The output is buffered by A3. When the gate is driven to V-for hold, it pulls the charge out of the hold capacitor. A compensating charge is put into the hold capacitor through C3. The step.....

Track-and-hold-sample-and-hold

Channel 1 is wired as a voltage follower and is turned on during the track/sample time. Ifthe product of R x Cis sufficiently short compared to the period of maximum output frequency, or sample time; Cwill charge to the output level. ..

Tachometer

A standard shaft encoder"s A and B ports generate square waves with the same frequency as the shaft turns. The phase of A will lead or lag that of B by 90Â°, ~depending on the direction of rotation. To obtain maximum resolution, the tachometer circuit must count every change of the state for the A and B signals. Each such change causes a change of state at IC1A"s output, followed by a 1-!LS negative pulse at the output of IClC. These clock pulses" positive (trailing).....

Low-Cost Barometer

Using Linear Technology LT1027 reference and LT1078 op amps, transducer T1 is fed with 1.5 mA. The pressure transducer f..

Capacitor Esr Measurer

The equivalent series resistance (ESR) of a capacitor can be measured using this circuit and an ac voltmeter. Ul fun..

Harmonic Distortion Analyzer Circuit

The circuit includes a low-distortion, 1-kHz oscillator and will measure THD at a user selected voltage level for voltage amplifiers, or for checking amplifiers of power levels to 600 W. It will detect THD levels of .005% (-86 dB). A built-in one-percent THD calibrator is included. ..

Calibrated-tachometer

Here is a simple tachometer circuit for use with a hand-held DVM or portable chart recorder. A novel feature is that the source frequency pulse/rev rate can be directly set on a ten-turn potentiometer to provide a convenient calibration of one V per 1000 rev/min. This is particularly useful when measuring a shaft or engine speed by sensing gear teeth. ..