Non interacting zero and span. how?
Robert A. LaBudde email (remove spam text)
<x-flowed>At 07:22 PM 5/20/00 -0400, Chris wrote:
>To simplify the problem, say I have an op amp circuit with an input
>signal of 0-5VDC and a desired output of 1-5VDC. I have a zero and a
>span pot. Normally, I build this circuit with the zero pot and the
>signal in question summed with two resistors into the + pin of the amp.
>Then wrap the output back to the negative pin with a pot for the span.
>The big complaint form customers is that the zero and the span interact
>a lot. My quest is to change the circuit so that the zero pot
>accurately sets the 1V level at 0V in, and then adjust the span pot for
>5V out at 5V in.
>By the way, the application is converting to 4-20mA. Any output where
>the ratio of low to high is 1:5 is acceptable. It does not have to be
>1V and 5V.
>The application in mind has split rails, but it would be nice to have a
>single supply solution for those other jobs too. Any grand ideas come
1. What is your current circuit?
2. What type of op-amp are you using?
3. Is an inverting configuration acceptable?
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: lcfltd.comral
Least Cost Formulations, Ltd. URL: http://lcfltd.com/
824 Timberlake Drive Tel: 757-467-0954
Virginia Beach, VA 23464-3239 Fax: 757-467-2947
"Vere scire est per causas scire"
In reply to: <39271E30.8CBCCFC3@nb.net>
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