Need help updating a circuit

redneckdan

May 29, 2011
3
Joined
May 29, 2011
Messages
3
Hi all,

I am working on a strain gauge based pressure measurement system.  The general idea is that a pressure spike, roughly 100 microseconds in duration, causes a voltage increase in the system which is stored in a capacitor through the use of zenior diodes.  This circuit was designed in the early 80s.  The instrument and op amps are rather expensive or non-existent.  I am wondering if I can find more modern/cheaper alternatives that will drop into the existing circuit or can be used with some circuit redesign.  Below is the diagram.

diagram.jpg



Thank you for your help.  My back ground is in mechanical design and I know just enough about circuit construction to be dangerous.  C4 is the capacitor that stores the voltage spike for measurement by a multi meter.

 

Hero999

Oct 28, 2007
2,433
Joined
Oct 28, 2007
Messages
2,433
The INA114 looks simialr to the AD521
http://focus.ti.com/lit/ds/symlink/ina114.pdf

The OPA128 is recommended to replace the AD515
http://www-micrel.deis.unibo.it/DATA_SHEETS/OPA128.pdf

You could also try contacting Analog Devices.

 

redneckdan

May 29, 2011
3
Joined
May 29, 2011
Messages
3
Thank you for the info.


I sent AD an email last night.  Probably won't hear anything until mid week.

 
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