[chbot] .5 offset voltage

[Mark Atherton]

Hi Wallace,

Input to the LED display is 0 to 5V and the output from the 
transducer is 0.5 to 4.5V and you wish to directly scale between the two ?

Sounds like you need a gain of 5.0 / 4.0 (output range over input 
range) a you also need to remove a 0.5V input offset assuming input 
and output signals are the same polarity...

Possible methods

a) opamp or two with some with some resistors

2) uP with ADC and DAC and some fixed point maths

iii) Assuming that the LEDs are driven by something like an LM3914, 
set Rlo and Rhi to 0.5 and 4.5 volts respectively and scaling and 
offset is done.

More details please...

-Mark


At 08:43 p.m. 17/07/2011, Marshland Engineering wrote:
>I have a 5 volt transducer and I need to measure the output. The 
>problem I have is the display and transducer both run off the same 
>power supply  (12 volts) but the transducers outputs range is 0.5 to 
>4.5 volts. The LED meter's input is not free floating. How do I get 
>the meter ground to be 0.5 volts above the transducer ground. As it 
>is an LED meter, the current will vary quite considerably with the 
>number of segments displayed so a simple dropper resister will not do ?