Datasheet

FSC[2:0]=400000h ´

ExpectedOutputCode

ActualOutputCode

ExpectedOutputCode=2 V ´´

REF

FSC[2:0]=400000h ´

ExpectedRMSValue

ActualRMSValue

ADS1281

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SBAS378D –AUGUST 2007–REVISED JUNE 2010

USER CALIBRATION The value written to the FSC registers is calculated

by Equation 8 and Equation 9.

System calibration of the ADS1281 can be performed

without using the calibration commands. This DC signal calibration is shown in Equation 8 and

procedure requires the calibration values to be Equation 9. The expected output code is based on

externally calculated and then written to the 31-bit output data.

calibration registers. The steps for this procedure are:

1. Set the OFSCAL[2:0] register = 0h and

GANCAL[2:0] = 400000h. These values set the

(8)

offset and gain registers to 0 and 1, respectively.

2. Apply a zero differential input to the input of the

system. Wait for the system to settle and then (9)

average n output readings. Higher numbers of

For ac signal calibration, use an RMS value of

averaged readings result in more consistent

collected data (as shown in Equation 10).

calibration. Write the averaged value to the OFC

(10)

3. Apply a differential dc signal, or an ac signal

(typically full-scale, but not to exceed 103%

full-scale). Wait for the system to settle and then

average the n output readings.

Product Folder Link(s): ADS1281