Changing DC level from a sensor

[JERD]

I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC.
Presumably with an op-amp?
Single supply IC preferable e.g. LM358
Appreciate some advice on how to accomplish this.

JERD

 

[Jasen Betts]

On 2010-08-31, JERD <notme@bigpond.net.au> wrote:

I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC.
Presumably with an op-amp?
Single supply IC preferable e.g. LM358
Appreciate some advice on how to accomplish this.

simple summing network:

.--R--0V
|
in --R-o-+\
| >-o--- out
2.5V -R-o--/ |
| |
`--R--'

dunno how close to 0V that'll go, use larger R if necessary.



--
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[terryc]

On Tue, 31 Aug 2010 10:50:26 +0930, JERD wrote:

I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC. Presumably with an
op-amp?
Single supply IC preferable e.g. LM358 Appreciate some advice on how to
accomplish this.

Put a 2v zener ad a resistor in series across the output and take the
reading off the resistors?

 

[Noodnik]

"JERD" <notme@bigpond.net.au> wrote in message
news:MNYeo.5026$FH2.2763@viwinnwfe02.internal.bigpond.com...

I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC.
Presumably with an op-amp?
Single supply IC preferable e.g. LM358
Appreciate some advice on how to accomplish this.

JERD

You haven't said anything about the accuracy you require. Backing out 2

volts with a simple zener is likely to result in a fairly unstable zero
point, as well as some added source resistance you may be better without. If
you want something a bit better you could build a standard diff amp from a
single supply opamp such as the one you suggest. Any opamp cookbook website
will have a schematic.

 

[Trevor Wilson]

"JERD" <notme@bigpond.net.au> wrote in message
news:MNYeo.5026$FH2.2763@viwinnwfe02.internal.bigpond.com...

I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC.
Presumably with an op-amp?
Single supply IC preferable e.g. LM358
Appreciate some advice on how to accomplish this.

**Buy yourself a copy of Walt Jung's 'OP Amp Coookbook'. You can work it out
for yourself. Alternatively, you can scan the Natsemi datasheets for some
common OP amps. There will probably be an application note suitable for your
needs.


--
Trevor Wilson
www.rageaudio.com.au

 

[Mark Harriss]

JERD wrote:

I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC.
Presumably with an op-amp?
Single supply IC preferable e.g. LM358
Appreciate some advice on how to accomplish this.

JERD

Does it have to go down to zero?, if not, a resistor divider could work
fine.

 

[JERD]

"Mark Harriss" <billy@blartco.co.uk> wrote in message
news:WaidnX_eQOlXDuDRnZ2dnUVZ8s2dnZ2d@westnet.com.au...

JERD wrote:
I have a sensor whose output varies from +2.5 volts DC to + 4.5volts DC.
I would like to 'shift' this to become 0 - 2volts DC.
Presumably with an op-amp?
Single supply IC preferable e.g. LM358
Appreciate some advice on how to accomplish this.

JERD




Does it have to go down to zero?, if not, a resistor divider could work
fine.

Thanks for all replies of assistance.

My preference is for it to go to zero.

I am going to have a try of all of the suggestions and increase my knowledge
at the same time. At age 68 the brain doesn't work as well as I would like
these days!

JERD