DAQ full scale range vs. gain vs. resolution?

[John Muchow]

With a DAQ module like the NI USB-6008
(http://sine.ni.com/nips/cds/view/p/lang/en/nid/14604) or DATAQ DI-158
(http://www.dataq.com/products/startkit/di158.htm) how does the gain
setting affect the resolution of the measurement?

For example, asusme a DAQ has a 10-bit input channel, +/-10V "full
scale range", and gains of 1,2,4,8, If I set the gain to 1, I should
then have 1024 steps from -10 to +10 volts, or a resolution of
0.01953V (20V / 1024 steps).

Does that mean if I set the gain to 4, I'll have a full-scale range of
+/-2.5V and a resolution of .00244V (5V / 1024 steps)?

Or do I always have that same (approx) .020V resolution? I'm pretty
sure that's not the case, but I wanted to make sure.

Thanks!
John Muchow
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[Bob Masta]

On Wed, 24 Aug 2005 08:01:49 GMT, John Muchow
<jmuchow@SPAMMENOTcamlight.com> wrote:

With a DAQ module like the NI USB-6008
(http://sine.ni.com/nips/cds/view/p/lang/en/nid/14604) or DATAQ DI-158
(http://www.dataq.com/products/startkit/di158.htm) how does the gain
setting affect the resolution of the measurement?

For example, asusme a DAQ has a 10-bit input channel, +/-10V "full
scale range", and gains of 1,2,4,8, If I set the gain to 1, I should
then have 1024 steps from -10 to +10 volts, or a resolution of
0.01953V (20V / 1024 steps).

Does that mean if I set the gain to 4, I'll have a full-scale range of
+/-2.5V and a resolution of .00244V (5V / 1024 steps)?

Correct.

Or do I always have that same (approx) .020V resolution? I'm pretty
sure that's not the case, but I wanted to make sure.

The gain is applied before the A/D converter, so the result is
just as you thought.

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[John Muchow]

The gain is applied before the A/D converter, so the result is
just as you thought.

Excellent, thanks!
John Muchow
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