Wednesday, January 06, 2016

Two Op-Amp Differential Amp

This is an ideal circuit for sensor amplification. Strain Bridge circuits too. It is an instrumentation amplifier, means precision. High input impedance to a differential input signal source. The gain can be set with external resistors to over 1000. CMRR trim to match resistor network.

Linear Technology Circuit Two Op Amp Instrumentation Amplifier

Two Op-Amp Differential Amp

I measure Instrumentation Amplifier like this - Tera Ohms Impedance, Pico Amps Bias Current. Micro Volts Offset Voltage. Here is a Interactive demo i built for such a configuration. The Input Impedance of this module is very high and is symmetric. This circuit can be used for strain gauges and for four wire measurements. If inputs are in mV use OP07. The merit is that it uses only 2 OpAmps yet has high differential Input Impedance.

Dual Op-Amp Differential Amp Tutorial

The Outputs of Opamps are low impedance but still have limits they cannot drive more than a few mA of Current into the Load. If low ohmic value loads are to be applied use external transistors as amplifiers. If inputs Vn-Vp are floating, outputs may be random or oscillating, it is good to have a bias network of 10M resistors to a potential even zero or common, this enables some Vout when input floats.

Friday, January 01, 2016

Raspberry Pi and MSO-28 Virtual Scope

PiMSO, is a Raspberry Pi controlled 200Msa/s mixed signal oscilloscope.  PiMSO, a spinoff of WebMSO, is an experimental project to understand the necessary components required to deploy the MSO-28 mixed signal oscilloscope on mobile devices.

The PiMSO lets you run a USB based Oscilloscope/Logic Analyzer from a Raspberry PI. The Oscilloscope is controlled via the browser on phone, tablet, PC or MAC. The connection to the host is via WIFI or Ethernet.  PiMSO consists of eight parts:

 Raspberry Pi and MSO-28 Virtual Scope

The MSO-28 is a 2 GSa/s Oscilloscope and 200 MSa/s Logic Analyzer. It is extremely portable.

The MSO-28 has time synchronized oscilloscope and logic analyzer inputs. All 10 channels are sampled at the same time and are displayed together. This is better than separate instruments because the analog and digital waveforms are acquired with the same sample clock assuring accurate time correlation between the two.

Add a RaspberryPi or Intel Edison for remote operation via the web.  Control the MSO-28 remotely from your Android, IOS or web browser.

delabs Schematics