True RMS-to-DC IC

MX536A and MX636
Maxim-IC
The MX536A and MX636 are true RMS-to-DC converters.
They feature low power and are designed to accept
low-level input signals from 0 to 7VRMS for the MX536A
and 0 to 200mVRMS for the MX636. Both devices accept
complex input waveforms containing AC and DC components.
They can be operated from either a single supply
or dual supplies. Both devices draw less than 1mA
of quiescent supply current, making them ideal for battery-
powered applications.






Feature
- True RMS-to-DC Conversion
- Computes RMS of AC and DC Signals
- Wide Response:
2MHz Bandwidth for VRMS > 1V (MX536A)
1MHz Bandwidth for VRMS > 100mV
- Auxiliary dB Output: 60dB Range (MX536A)
50dB Range (MX636)
- Single- or Dual-Supply Operation
- Low Power: 1.2mA typ (MX536A)
800μA typ (MX636)


Mx536,MX636 datasheet pdf

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
voltage.

True RMS-to-DC Converter

AD736
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.

Provides
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

AD736 datasheet pdf

Application Note True RMS-to-DC Converter

RMS-to-DC converter circuit

LTC1966
Precision Micropower,RMS-to-DC Converter

The LTC1966 is a true RMS-to-DC converter that utilizes
an innovative patented computational technique. The
internal delta-sigma circuitry of the LTC1966 makes it simpler
to use, more accurate, lower power and dramatically
more flexible than conventional log-antilog RMS-to-DC
converters.

LTC1966 datasheet pdf

Instrumentation Circuitry Using RMS-to-DC Converters

Measuring rms voltage