Re: Automatic gain control

Victor hyppolito wrote:
I know your point! How can the "MAGIC BOX" know its 0,01V(full scale of
a 0-10mV) or a 50% of a 0,02V.
But I would calibrate it(make it go to full scale) and then have a 5V
at the output.
For exemple. A 0-10mV input signal with gain=500 would give me a 5V at
the output. Now, with the same Gain=500 I can have a 0-20mV input
signal and force it go to full scale(for exemple, compressing my strain
gauge all the way so that it goes to full scale), my output would be
10V, right? But isn´t there anything that can make this go to 5V and
record this proper gain(in this case, 250) to use afterwards?
This way, when I enter this "calibration mode" , whatever is the input,
the "MAGIC BOX" would know it is the full scale input"! Understand?
Maybe it is too hard to implement, maybe not... That´s why Im asking
you guys because (many of you) are professionals and have a lot of
experience. If you say it´s something for a doctor thesis, I give up!
:-)
Regards!
Victor


OK, back to electronics.
If I understand the whole issue, you want full scale output constant at any full scale output of your bridge, disregarding the sensitivity of your strain gauges.
So you have to calibrate your bridge to give you certain, part scale output, and adjust your gain accordingly, either by precisson potentiometer which you lock in position for this measurment or by AGC which should be still somehow locked constant during measurment.
The known unbalance you create by applying parralel resistor to one side of your balanced bridge to create a simulation of stress. You have to calculate what stress it represents, depending on resistance of the particular batch of gauges you use. (If you use semiconductor gauges I cannot help you as the resistances have very wide resistance range and its change with temperature may be out of usefull precission.)
So for the manual gain control you can use DC excitment of the bridge and get DC output.
For AGC try AC, then you go to AC amplifier and life is easy. The detector may be a little more complicated as it has to inform you if the bridge is under tension or compression so your AC acts as carrier to ballanced detector.

Been there, used it!

Have fun

Stanislaw
Slack user from Ulladulla.

.

Relevant Pages

  • BUM-RAP Redux
    ... 3-2-1-0.5, in the Bridge World. ... 4A's scale but after extensive discussions on RGB he adjusted it to: ... points but only as 9 B-R points and four Aces count as 16 on the W ...
    (rec.games.bridge)
  • Re: BUM-RAP Redux
    ... 3-2-1-0.5, in the Bridge World. ... 4A's scale but after extensive discussions on RGB he adjusted it to: ... points but only as 9 B-R points and four Aces count as 16 on the W ...
    (rec.games.bridge)
  • Re: BUM-RAP Redux
    ... 3-2-1-0.5, in the Bridge World. ... 4A's scale but after extensive discussions on RGB he adjusted it to: ... points but only as 9 B-R points and four Aces count as 16 on the W ...
    (rec.games.bridge)
  • My new badass axe revisited
    ... Screws that adjust the intonation on bridge ... Sound ain't too bad for small scale length. ... Typical strings attached to plate at bridge. ...
    (rec.music.makers.guitar.jazz)
  • Re: Basses with narrow string spacing?
    ... Are these all short scale? ... >> Framus 'Star' Bass. ... >>> tend to play the Danelectro more because of the super light weight, ... Just cast a ruler over the Schaller 3D4 bridge on my self built fretless, ...
    (alt.guitar.bass)
Quantcast