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Strain Gauge Measurement Circuit Based on Analog Devices Components and Applicaion Note in Multisim 12

Hello Circuit Designers,

Multisim's component database is equipped with over 22,000 industry-standard components provided by leading semiconductor manufacturers, allowing Multisim users to accurately evaluate their design performance and optimize it before handing it over to prototyping.

National Instruments partnership with Analog Devices allows designers to model, simulate, and prototype over 800 Analog Devices parts in Multisim's database, most of which are operational amplifiers.

In the application note AN-683 the following components were used to create a strain gauge measurement application, where a signal is sensed and acquired using strain gauge sensors and then processed and filtered to provide accurate readings; these components are:

AD8221: The AD8221 is a gain programmable, high performance instrumentation amplifier that delivers the industry’s highest CMRR over frequency in its class. The CMRR of instrumentation amplifiers on the market today falls off at 200 Hz. In contrast, the AD8221 maintains a minimum CMRR of 80 dB to 10 kHz for all grades at G = 1. High CMRR over frequency allows the AD8221 to reject wideband interference and line harmonics, greatly simplifying filter requirements. Possible applications include precision data acquisition, biomedical analysis, and aerospace instrumentation.

AD630AR: The AD630 is a high precision balanced modulator that combines a flexible commutating architecture with the accuracy and temperature stability afforded by laser wafer trimmed thin film resistors. Its signal processing applications include balanced modulation and demodulation, synchronous detection, phase detection, quadrature detection, phase-sensitive detection, lock-in amplification, and square wave multiplication.

OP1177: The OPx177 family consists of very high precision, single, dual, and quad amplifiers featuring extremely low offset voltage and drift, low input bias current, low noise, and low power consump-tion.

The application circuit is shown in the snippet png image below (you can directly drag and drop it into Multisim 12)

Strain Gauge Measurement.png

In Multisim, the bridge on the left hand side is excited using an AC signal, the AD8221gains the signal, and the AD630AR synchronously demodulates the waveform. For more information on the design, refer to the original Analog Devices application note AN-683.

In this design, the resistor R9 is used to model the strain gauge sensor and a parametric sweep analysis is run to view the DC level of the output signal at various input points.

Here is a screenshot of the sweep analysis settings

Strain Gauge Measurement2.PNG

And the results of the analysis, show that with every input point a different DC level is achieved, with a high Common Mode Rejection Ratio at a bandwidth up to a bandwidth of 10 kHz prvided by the AD8221 amplifier

Strain Gauge Measurement3.PNG

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