Re: Need to design precision 5mA constant current source (wide temp range).. need help

From: stevo (stephendeese_at_hotmail.com)
Date: 11/23/04 

Date: 23 Nov 2004 08:19:10 -0800

The spec *** for the bridge has the following:

Sensitivity tempco:
Vbridge= 8V (constant voltage) 0.3 %/C
IBridge = 5mA 0.06 %/C

So, it appears that the bridge is more stable w/ the constant current.

John Popelish <jpopelish@rica.net> wrote in message news:<41A293D6.463EBE3E@rica.net>...
> stevo wrote:
> >
> > Hi,
> >
> > I need to design a 5mA constant current source for a Wheatstone bridge
> > application. The problem is the source needs to be +- 3% accurate and
> > hold that accuracy over a -40 C to +85 C temperature range.
> >
> > I have thought about using a simple FET CCS, but don't have much
> > experience and am not sure if I can make it accurate enough.
> >
> > Can any of you more experienced guys point me in the right direction?
> >
> > Thank You
> > Stephen
> >
> > Ohter info : V avalible +15V; bridge resistance ~ 850 ohms
>
> Are you sure that a constant voltage across the bridge would not
> improve its accuracy?

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