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ADAS3022 Problem PGIA Gain 0.16

Question asked by gligli on Mar 7, 2016
Latest reply on Apr 4, 2017 by Gnib

hello,

I am using ADAS3022 to make a DAQ system to measure 0~24Vdc signal.

So I set PGIA to 0.16 (000), then input a DC voltage to IN0-COM and display in LabVIEW. VDDH = 15V, VSSH = -15V, DVDD = AVDD = 5V.

The test steps are below:

1. Input 10Vdc, the measured value is 0x33FD.  (10 / 24.576) * 32768 = 13333 = 0x3415 ≈ 0x33FD.

Now, the input current is about 0mA. And the VDDH is 15V.

step1.png

2. Input 15Vdc, the measured value is 0x4DF6. (15 / 24.576) * 32768 = 20000 = 0x4E20 ≈ 0x4DF6

step2.png

3. Input 16Vdc, measured signal looks bad. (16 / 24.576) * 32768 = 21333 = 0x5355.

step3.png

4. Input 19Vdc, measured value is much lower than actual value. (19 / 24.576) * 32768 = 25333 = 0x62F5.

Now, the input current is about 7mA. And the VDDH changed to 18.5V, but I set VDDH to 15V by ADP1613.

step4.png

 

The schematic is blow:

sch.png

 

Is there something wrong when I use ADAS3022?

Thank you!

Regards,

Jin

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