Electronic Device And Electronic Circuit

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Wednesday, December 19, 2007

RMS to dc Circuit

Circuit measures true-rms and average value
The circuit measures both the true-rms value and the
rectified average value of an ac signal.This design uses
two low-cost ICs
Operating from a single 5V supply, the circuit has an
input dynamic range of less than 30 mV to greater than 3V rms.

RMS-to-dc converter Circuit is accurate and stable
The circuit uses a low-cost analog multiplier, IC1; an
integrator, IC3A, R5, and C1; and an analog inverter, IC2, R3, R4,
and D1 to convert the analog VIN into a true-rms dc VOUT.
The input signal can be ac, dc, or a combination. With an
input-signal range of 0 to 2V, the circuit can handle ac signals
with crest factors up to 5

True RMS Detector Circuit
The op amp precision rectifier circuits have greatly eased
The problems of AC to DC conversion. It is possible to measure
millivolt AC signal with a DC meter with better than 1%
accuracy. Inaccuracy due to diode turn-on and nonlinearity is
eliminated, and precise rectification of low level signals isobtained

Extend RMS-To-DC Converter's Range
The AD736 rms-to-dc converter is a 1-V, full-scale device.
Voltage comparator IC3 can increase the full-scale input range to
10 V automatically. When the rms-to-dc operating range is exceeded
, the comparator's hysteresis switches in an attenuator at the
rms-to-dc converter's input. Concurrently, it adds a gain stage to
the circuit's output-buffer amplifier, maintaining a steady output


Wednesday, December 12, 2007

True RMS-to-DC Converter

Analog Devices, Inc.
The AD736 is a low power, precision, monolithic true rms-to-dc
converter. It is laser trimmed to provide a maximum error of
0.3 mV 0.3% of reading with sine wave inputs. Furthermore,
it maintains high accuracy while measuring a wide range of
input waveforms, including variable duty cycle pulses and triac
(phase) controlled sine waves.

200 mV full-scale input range (larger inputs with input attenuator)

High input impedance: 1012 Ω Low input bias current: 25 pA maximum

High accuracy: ±0.3 mV ± 0.3% of reading

RMS conversion with signal crest factors up to 5

Wide power supply range: +2.8 V, −3.2 V to ±16.5 V

Low power: 200 µA maximum supply current

Buffered voltage output

No external trims needed for specified accuracy