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DIGITAL pH METER – Circuit Schematic
DIGITAL pH METER
3130 CMOS opamp gives required high input impedance for pH probe at low cost. Output of probe, ranging from positive generated DC voltage for low pH to 0 V for ...
LIGHT METER WITH LED READOUT – Circuit Schematic
LIGHT METER WITH LED READOUT
Light onphototransistorQ1 (Radio Shack 276-130) produces voltage change across R2 for amplification by opamp whose output drives array fiveLEDs forming bar grap...
THERMOMETER ADAPTER – Circuit Schematic
THERMOMETER ADAPTER
A simple op amp and silicon diode are the heart of the temperature-to-voltage converter that will permit you to use an ordinary voltmeter-either analog or digit...
TEMPERATURE REPORTING DIGITAL THERMOMETER – Circuit Schematic
TEMPERATURE REPORTING DIGITAL THERMOMETER
The ROMs or PROMs must have the correct code for converting the data from the NE5037-used as address for the ROMs or PROMs-to the appropriate segment driver cod...
MHz FREQUENCY COUNTER – Circuit Schematic
MHz FREQUENCY COUNTER
This is a schematic and block diagram of a 2-MHz frequency counter. It uses and LSI counter/display driver, LCD readout, and a, few logic chips for timebase and...
FREQUENCY COUNTER PREAMP – Circuit Schematic
FREQUENCY COUNTER PREAMP
By using the preamplifier with a short length of shielded cable and clip leads, signals that generally could not generate a readout, generate precise and stable...
10 MHz FREQUENCY COUNTER – Circuit Schematic
10 MHz FREQUENCY COUNTER
The circuit consists of ICM7208 seven-decade counter U1, ICM7207A oscillator controller U2, and CA3130 biFET op amp U3. IC UI counts input signals, decodes them...
CAPACITANCE METER – Circuit Schematic
CAPACITANCE METER
U1a is an oscillator and U1b the measurement part of the circuit. It converts unknown capacity into a pulse-width modulated signal the same way an automotive dw...
SOIL MOISTURE METER – Circuit Schematic
SOIL MOISTURE METER
IC1, an Intersil ICL7106, contains an a/d converter, a 3 1/2-digit LCD driver, a clock, a voltage refer-ence, seven segment decoders, and display drivers. A sim...
FREQUENCY COUNTER PREAMP – Circuit Schematic
FREQUENCY COUNTER PREAMP
Based on the LM733 or NE592, the preamp shown has a bandwidth of 100 MHz. The FET inputs provide about 1-M © input impedance. Q4, Q5, and IC2 provide signal co...
JFET VOLTMETER – Circuit Schematic
JFET VOLTMETER
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BAR GRAPH VOLTMETER – Circuit Schematic
BAR GRAPH VOLTMETER
This display uses ten LED`s to display a voltage range from 10. 5 to 15 volts. Each LED represents a 0. 5-volt step in voltage. The heart of the circuit is the ...
FET VOLTMETER – Circuit Schematic
FET VOLTMETER
This FETVM replaces the function of the VTVM while at the same time ridding the in-strument of the usual line cord. In addition, drift rates are far superior to...
HETERODYNE FREQUENCY METER – Circuit Schematic
HETERODYNE FREQUENCY METER
Circuit consists of 1-2 MHz oscillator Q1, untuned mixer X1, and AF beat-note amplifier Q2. C4 is calibrated to read directly in frequency from 1 to 2 MHz, usin...
AUDIO FREQUENCY METER – Circuit Schematic
AUDIO FREQUENCY METER
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5 mA S METER – Circuit Schematic
5 mA S METER
Circuit designed for 5-mA meter movement uses two-stage voltage ampilfer Q1-Q2 with emitter-follower output Q3 serving as impedance-matching stage AF input for ...
BASIC DIGITAL THERMOMETER KELVIN SCALE WITH ZERO ADJUST – Circuit Schematic
BASIC DIGITAL THERMOMETER KELVIN SCALE WITH ZERO ADJUST
This circuit allows zero adjustment as well as slope adjustment. The ICL8069 brings the input within the common-mode range, while the 5 K pots trim any offset a...
VARICAP TUNED FET DIP METER WITH 1 kHz MODULATION – Circuit Schematic
VARICAP TUNED FET DIP METER WITH 1 kHz MODULATION
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CENTIGRADE CALIBRATED THERMOCOUPLE THERMOMETER – Circuit Schematic
CENTIGRADE CALIBRATED THERMOCOUPLE THERMOMETER
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VSWR METER – Circuit Schematic
VSWR METER
Simple, easily transported VSWR meter consists of high-gain amplifier, narrow-bandwidth (100-Hz) selective amplifier tuned to 1000 Hz, and variable-gain output ...