XTR108EA-2K5 BURR-BROWN [Burr-Brown Corporation], XTR108EA-2K5 Datasheet - Page 20

• Manufacturer Part Number: XTR108EA-2K5
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

6) Choose PGA gain from the available list and calculate
7) The required DAC zero offset current value can be
Example:
Measurement Range: T
RTD.
1) R
2) Sensor relative nonlinearity: B
3) Choosing R
4) Linearization coefficient: G
5) 4-20mA output span;
6) PGA voltage gain A
7) Zero offset DAC: I
CALIBRATION PROCEDURE FOR RTD SENSORS
Step 1 Initial parameters calculation.
• Using the procedure above, compute I
• Configure the input MUX, write PGA gain, reference,
Step 2 Measurement.
• Set RTD resistor value (or oven temperature) to mini-
• Set RTD resistor value (or oven temperature) to maxi-
20
I
REF
Important: the PGA gain value should be chosen such
that the I
allow room for calibration adjustments without having
to go to another span step.
and G
R
calculate the DAC register values.
and offset DAC registers of the XTR108 with calcu-
lated settings. Note: write G
XTR108 at this step;
mum scale, measure output signal I
mum scale, measure output signal I
1 2
the initial excitation current using:
calculated by:
I
Z
,
REF1,2
, R
MIN
I
ZERO
SET
LIN
I
= 92.16 , R
OUT
= 368.39mA;
, and R
REF
based on T
MAX
I
OUT
value is within 35% of 5V
Z
= 90.9
–
MIN
VI
I
50
OUT
. Use the equation in Table XV to
MAX
–
ZERO
MIN
PGA
MIN
MIN
50
A
PGA
, T
= 119.40 , R
(closest to R
= 200, sensor excitation current
= –20 C, T
= 3.268mA
A
MAX
1
LIN
PGA REF
–
LIN
R
G
, and nominal values of
= 0 (no linearization) to
MAX
I
V
LIN
= 0.3804mA/V;
R
= 0.0026;
VI
MEAS1
MEAS2
–
MAX
R
MIN
R
REF
R
MID
MAX
MIN
MIN
, A
;
;
= 50 C; 100
REF
2% value);
= 105.85 ;
–
–
PGA
/R
R
R
Z
SET
Z
, I
ZERO
to
R
www.ti.com
VI
,
Step 3.
• Calculate corrections using the following equations:
• Update all the DAC register value, including lineariza-
Step 4 (optional).
Measure output signal I
still connected to the input from step 2;
Step 5 (optional).
Compute G
Step 6 (optional).
Make verification measurements at min- and max-input
signal; If linearity check is needed: make a measurement at
mid-scale; write EEPROM data.
Step 7.
Set the desired over-scale, under-scale signal limits and
sensor burnout indication configuration. Verify and adjust
the over-scale and under-scale levels by applying the posi-
tive and negative overdriving differential signals to the PGA
inputs.
Adjusted I
Adjusted I
This takes into account resistor value deviations, all
offsets and gain errors of the coarse DACs and PGA. If
the adjusted abs(N
the coarse DAC first, then recalculate the fine DAC
value;
tion DAC.
I
REF B
G
I
ZERO
LINA
REF
ZERO
I
OUT MAX
LIN
fine DAC Code N
fine DAC Code N
I
R
OUT MIN
0 5
I
Z
I
correction and update LinDAC register;
.
REF
REF
A
–
A
B
R
I
V
OUT MIN
–
MIN
12A
I
REF
50
R
I
50
ZERO
I
MAX
) > 128 or abs(N
MEAS
A
MEAS3
:
–
A
PGA
:
I
10
PGA
I
REF A
–
ZERO
–
12
2
A
50
50
1
R
0 5
A
–
2
–
. –
A
MAX
with maximum RTD value
I
B
N
MEAS
G
–
R
PGA REFA
A
V
10
N
LIN A
MAX
I
B
PGA REF
I
12
MEAS
REF
V
–
I
_
1
R
round
I
R
–
round
R
MIN
–
1
MIN
R
R
VI
R
I
R
MIN
10A
REF B
B B
MAX
VI
VI
–
R
1024
) > 128, adjust
2
MIN
–
512
B R
V ZA
R
–
Z A
5
XTR108
V
R
SBOS187C
REF
I
Z A
I
V
REF SET
ZERO VI
REF
R
R
VI
R