minki

後日就present..
royal1108 發表於 2011-5-10 22:09

WA:funk:

越野兔

royal1108,
Qs for your your home made amp-board:
1. what's the voltage supply of your home made amp-board,BOTH +12V and -12V?
2. what's the value of R7?
3. what's the value of R5?
4. what's the measured resistance value (using DVM when powered-off the amp-board) between pin2 & pin6 of U1 ?

越野兔

minki 兄,可能小弟講到大家有誤會..其實我係想話arduino的analog input最盡是0-5v....應該是我表達錯誤... ...
royal1108 發表於 2011-5-10 17:09

your strain gauge amplifier driving display module with errors?
what's the current output capability of your rs 435-692 strain gauge amplifier?
what's the input dc-resistance of your display module?

越野兔

minki 兄,可能小弟講到大家有誤會..其實我係想話arduino的analog input最盡是0-5v....應該是我表達錯誤... ...
royal1108 發表於 2011-5-10 17:09

i can imagine your fyp (pressure sensor) is inaccurate and non-linear.

越野兔

其實小弟搞甘多野,都係為左做到個display 可以準確睇到個數值,,
同時地考慮 那1個位可以quit一條線出來用 ...
royal1108 發表於 2011-5-10 20:19

may be the following basic concepts are helpful to you and your fyp report: ohms law, dc-amplifier, output current capability, input resistance, input buffering, amp-linearity, zero-crossing distortion, a/d reference, a/d quantization, specification/user manual study, etc..........

越野兔

亦可能係DC OFFSET
minki 發表於 2011-5-10 21:34

    it should be some loading problem, due to insufficient output current .........

越野兔

小弟決定聽日用e個方面 博一博..因為...後日就present...爛尾就爛尾...爛尾之中..我係有學到野...學識解決 ...
royal1108 發表於 2011-5-10 22:09

除非你super係李剛 .......

KSC

看到這兒我想大家都知乜事

首先你誤解了MCU的ADC能力和program的關係
ADC的Vref就像攝影的光學變焦，改變它可以更準,加強訊息的分析力
程序放大就像數碼變焦，對訊息沒有實際意義

以arduino做analog input的話它的Referance是5V(如你沒有改它的Vref),對應的電壓是0~5V,輸出數值0~4096
即每0.00122V數值改變1
ie: 0.0012 ==>1
0.0025==>2
0.0074==>3
0.122==>100
0.1232==>101

以你的例子
1.6mV是大概在1或2在跳
如果你用程序做放大
val=val*100
0==>0
0.0012 ==>100
0.0025==>200
0.0074==>300
0.122==>10000
0.1225==>10000 or 10100
0.1232==>10100
是沒有中間的數值的


正確做法是將類比輸入的電壓放大,不是用程序
ie
0.0012V==>0.12V==>100
0.00125V==>0.125V==>104
0.001232V==>0.125V==>110

opamp方面，唔知點解你會有咁樣用opamp的做法.......而因為你完全不按規則來,輸出不一致是好正常的
你只係放大訊號用non-invert的接法咪ok low....單電源都做到