User`s guide

Elan Digital Systems Ltd. 41 AD125 USER’S GUIDE
AD1x1, AD1x2
INPUT IMPEDANCE: ≈ (4000 + 10
9
/ Fin) Ω (SINGLE ENDED)
! Avoid significant source impedance if you are
digitising AC components with relatively high
frequencies. To avoid attenuation > 1LSB the source
impedance should be 4096 times less than the above
calculated value. The frequency dependent nature of the
input impedance can be used to affect extra anti-aliasing
by deliberately adding source impedance to your signal
and so attenuating higher frequencies. At DC the input
impedance is >10Meg.
INPUT BANDWIDTH: AD1x5, AD1x6 : 250KHz TYP +/- 20%
AD1x2 : 120KHz TYP +/-20%
AD1x1 : 50KHz TYP +/-20%
ANTI-ALIASING: OUT OF BAND ROLL-OFF APPROX 60dB/DECADE
FOR AD1x5 AND AD1x6 OR 40dB/DECADE FOR
AD132 AND AD1x1.
DACS: TWO LOW SPEED 12-BIT DACS ON MF SERIES
CARDS
DAC RANGES: EACH DAC OUTPUTS 0→2.5V AND -10V→+10V
ACCURACY: 0→2.5V RANGE ±0.5%, -10V→+10V ±0.9%
DAC O/P IMPEDANCE: 10O TYP.
DAC SETTLING TIME: <100us WITH 30pF LOAD TO 1LSB
DAC DRIVE: 1mA MAX EACH OUTPUT
ADC CALIBRATION: ON-CARD FACTORY CALIBRATION
COEFFICIENTS FOR MAIN GAIN RANGES CAN BE
USED BY APPLICATION SOFTWARE TO
CORRECT OFFSET AND GAIN ERRORS IN ADC
AND FRONT END.
5.2.1 CALIBRATION DATA
There are 18 calibration data values stored in the card’s E². You can
access these using PCCARDGO function call
ReadAttributeMemory( ) and a string search technique. These
values can be used to make a first order correction to zero and full
scale errors for the 5 most commonly used gain settings
(0.25,0.5,1.0,2.0,4.0). Other gain ranges can be approximated from
these 5 as they are derived using the same circuitry.
Explanation of symbols: