Circuits FAQ

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Friday, November 21, 2014

Digital weight Indicator - Strain Gauge

I need some details of a digital weight Indicator.
mail from CA

Digital Weight Indicators and Weighing Scales use Strain Gauges mounted on a Stressed Beam, Cantilever or Plate which is also Elastic, means springs back to old shape.

Digital weight Indicator - Strain_gauge

Strain Gauges are bonded to these plates and connected in a Wheatstone bridge circuit. The output of these are very low, as less as 5mV. These are amplified close to the sensor and usable outputs in volts, like 0-10V are used to display the parameter or control the systems.

Fluids Weights are measure with pressure sensors also. Which also have a mini strain gauge or piezoelectric sensor to convert weight to millivolts.

study these useful links.......

Introduction to Load Cells at Omega

A load cell is a transducer which converts force into a measurable electrical output

LC101 S-Beam Load Cell

S-Beam Load Cells S-Beam load cells get their name from their S shape. S-Beam load cells can provide an output if under tension or compression.

Measuring Strain with Strain Gauges at NI

"The metallic strain gage consists of a very fine wire or, more commonly, metallic foil arranged in a grid pattern."

delabs

Monday, November 10, 2014

Isolated Full-duplex Serial Interface

I would like to build Optoisolated RS232 interface. I've googled a little bit, and I came across your design:

RS232 with Opto-Isolation

However presented schematic is of poor quality - I'm not able to read all parts numbers and their values. Is it possible for you to send me a copy of this schematic, which is more readible?

Mail from M from Poland

You had written to me a few months back, I suggest this circuit

Isolated Full-duplex Rs232 Interface

This self powered interface circuit electrically isolates the TxD and RxD lines from the PC serial port and protect the PC from direct connection to hazardous voltages.

See also Isloated Interface to Microcontroller

See a Commercial Solution you can buy

CVT-232A-3 port-powered 3-wire RS232 Isolator

CVT-232A-3 port-powered 3-wire RS232 Isolator

"The unit features 5000V opto-isolation circuitry and optically isolates three (3) RS-232 lines (TX, RX and GND), which effectively protects your RS-232 devices from ground loops, noise problems, transient surges, remote lightning and spikes."