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Voltage reg or voltage reference.

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Screech

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I'm using a rotary position sensor as a voltage divider.

I'm also feeding this rotary position sensor with a simple voltage reg (eg.7808).
But the voltage regulator tolerance is plus-minus 5% :?

Does that meens my positon sensor could be out by 10% from time to time? :evil:

I don't mind if the voltage going into the positon sensor it's out, but I dont want the voltage going up or down due to heat, etc.
Just want it to be a stable voltage.
are they stable in heat/cold/ etc.


Any suggestions?

:idea: Zener diode? whats there tolerence?
:idea: My RS catalog has some Voltage reference gizmos.
are they suited to this job?

Thanks again.
 
if you want a precision voltage, then obviously a voltage reference is a much better choice, because they're designed to hold a precise voltage in all conditions, whereas a voltage reg is supposed to supply power, so it's not nearly as precise with its output voltage.

if you want to know the characteristics of the output voltage of a voltage reg, perhaps you should check out their datasheets!
 
Screech said:
But the voltage regulator tolerance is plus-minus 5% :?

Just want it to be a stable voltage are they stable in heat/cold/ etc.

The +/- 5% spec is the possible variation you will see from one device to another. If you buy a 7808 and measure its voltage, the voltage will be somewhere between 7.6V and 8.4 V.

In other words, if you test say 10 of the 7808 ICs, one may be 8.1 V, another 7.8 V, antoher 8.3 V, etc. This is the device tolerance.

The voltage of one particular 7808 will also vary a little with temperature, but that is a different issue. See the spec for the 7808.

Len
 
What are you sending this to? If it's an ADC then it will be accurate if you DON'T use a pvr.

Note a pvr usually can't put out much current, it may not be able to supply your device. It's called a "reference" instead of a "regulator" for that reason.

Check the spec sheet to see how much of that 5% is thermal variance. It may be quite a bit of it.
 
Think I test the regulator my self at different loads and temperatures, but I think I remember regulator voltages moving up and down at different loads.

And,
I only nead to supply 0.0003 Amps to the Rotary Position Sensor wich is a 5k pot.

I Still think a voltage reference might do the trick, even if I have never heard of them before.

Thanks.
 
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