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Help with a pressures sensor

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brentonw2004

New Member
Hello everyone. I recently purchased a Honeywell silicon piezoresistive pressure sensor off of Newark, and I was just wondering if anyone here has any advice on getting a PIC 16F819 to take a pressure reading from it and convert it to psi. I assume that I will have to use the PIC's analog to digital feature. I need help hooking it up. If anyone has a schematic it would really help. Here is a link with info on the sensor: http://catalog.sensing.honeywell.com/datasheet.asp?FAM=Pressure&PN=24PCDFA6G . I assume that I will supply it with a positive and negative voltage, but I don't know what to do about the positive and negative output voltages and how to get a reading off of it to my PIC. Any advice would be greatly appreciated. Thanks!
 

TheAnimus

New Member
Yes, the A/D converters on each PIC differ greatly, if you look in the datasheet for your choosen PIC, it will tell you which port and how to set the port up to act as an anolouge input.

If you look on microchip's website, it should help you in choosing a suitable PIC for your purpose.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
There's a "constant current exitation schematic" shown on the webpage you posted, that shows the sensor as a wheatstone bridge. You could feed the outputs from that into an opamp used as a differential amplifier - by correctly selecting the design you could easily make it amplify the 330mV maximum output range to something more suitable to feed to an ADC and ensure all values are positive at the same time. So you would end up with zero pressure reading 2.5V, with positive pressure causing this to rise, and negative pressure causing it to fall.
 

brentonw2004

New Member
How would I amplify the signal? Would a simple 386 do? Which would you amplify? The negative or positive output? Does anyone have a simple schematic showing how to amplify this? Thanks for your quick responses!!
 

Nigel Goodwin

Super Moderator
Most Helpful Member
brentonw2004 said:
How would I amplify the signal? Would a simple 386 do? Which would you amplify? The negative or positive output? Does anyone have a simple schematic showing how to amplify this? Thanks for your quick responses!!

You amplify them both, using a differential amplifier, the basic circuit looks like the one below.
 

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