參數(shù)資料
型號： XTR108EA
英文描述： 4-20mA, TWO-WIRE TRANSMITTER Smart Programmable with Signal Conditioning
中文描述： 的4 - 20mA，兩線制變送器可編程智能與信號調(diào)理
文件頁數(shù)： 19/27頁
文件大?。?/td> 497K
代理商： XTR108EA
XTR108
SBOS187B
19
www.ti.com
EXCITATION CURRENT I
REF
Coarse DAC code
N
round
I
V
R
REF
SET
REF
11
64
320
=
–
Fine DAC Code
N
round
I
R
V
N
REF
SET
REF
10
11
1024
5120
16
=
–
–
ZERO OUTPUT I
ZERO
Coarse DAC Code
Fine DAC Code
N
round
I
R
V
N
ZERO
VI
REF
12
13
512
5
2240
16
=
–
–
LINEARIZATION COEFFICIENT G
LIN
Lin DAC Code
N
round
G
R
LIN
LIN
14
16
(
=
)
RTD APPLICATION
The values to be entered into the DAC control registers are
given by the formulas in Table XV.
This procedure allows calculation of the parameters needed
to calculate the DAC codes for an RTD sensors application.
1) For a chosen temperature range, using an industry-stan-
dard polynomial set as shown in Table XVI, calculate
RTD values at min, max, and the middle temperatures:
(
R
R
andR
MIN
MAX
MID
,
,
)
2) Calculate a relative nonlinearity B
V
using the RTD values
from above:
R
MID
=
B
R
R
R
R
V
MAX
MIN
MAX
MIN
+
2
–
–
3) Pick an external zero resistor, R
Z
closest to R
MIN
. Select-
ing R
Z
greater than R
MIN
will cause a voltage offset that
must be corrected by the PGA zero adjustment.
4) Calculate the linearization coefficient::
G
B
B
R
B
R
B R
LIN
V
V
MAX
V
MIN
Z
=
+
(
)
(
)
2
0. –
0 5
.
2
–
–
If the value of G
LIN
is larger than G
LIN MAX
= (16/R
LIN
)
the external resistor R
LIN
has to be changed. If G
LIN
is significantly smaller (> 10 times) than G
LIN MAX
, the
R
LIN
value should be increased to minimize the DAC
quantization errors. For 100
RTD sensors the re-
quired linearization coefficients are in the range from
0.3 to 0.6 mA/V (1/k
) for all measurement ranges.
Therefore an external R
LIN
value of 15.8k
is good
setting the full-scale G
LIN MAX
~ = 1mA/V. For 1k
RTD’s the R
LIN
should be increased proportionally.
5)
Choose the output zero and full-scale level values, for
instance: I
OUTMIN
= 4mA, I
OUTMAX
= 20mA.
6)
Choose PGA gain from the available list and calculate
the initial excitation current using:
=
(
I
I
I
G
R
R
R
A
R
R
REF
OUT
OUT
50
LIN
MAX
Z
VI
PGA
MAX
MIN
MAX
MIN
1 2
,
1
(
–
–
–
)
–
)
(
)
(
)
Important: the PGA gain value should be chosen such
that the I
REF
value is within
±
35% of 5V
REF
/R
SET
to
allow room for calibration adjustments without having
to go to another span step.
7)
The required DAC zero offset current value can be
calculated by:
I
I
A
R
R
R
ZERO
OUT
PGA REF
MIN
Z
VI
MIN
=
(
)
–
–
50
Example:
Measurement Range: T
MIN
= –20
°
C, T
MAX
= 50
°
C; 100
RTD.
1)
R
MIN
= 92.16
, R
MAX
= 119.40
, R
MID
= 105.85
;
2)
Sensor relative nonlinearity: B
V
= 0.0026;
3)
Choosing R
Z
= 90.9
(closest to R
MIN
2% value);
4)
Linearization coefficient: G
LIN
= 0.3804mA/V;
5)
4-20mA output span;
6)
PGA voltage gain A
PGA
= 200, sensor excitation current
I
REF1,2
= 368.39mA;
7)
Zero offset DAC: I
ZERO
= 3.268mA
TABLE XV. Equations for DAC Code Calculation.
TABLE XVI. Standard RTD Descriptive Equations.
N
round
I
R
V
ZERO
VI
REF
13
32
5
140
=
–
S
dardRTD Polynomials
[
+
+
[
3 9083
3
5 775
7
4 183
12
R
R
At
B
C t
C t
°
for
C
t
C
R
R
At
B
for
C
t
C
A
B
C
R
e
e
e
base RTD value at
C
or k
t
O
t
O
O
tan
:
–
–
.
–
–
–
–
.
–
.
–
=
+
+
+
]
(
)
]
°
<
< °
0
=
°
<
<
°
=
=
=
°
(
)
1
1
100
200
1
1
0
850
0
100
1
2
3
2
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
XTR108EA/2K5 功能描述:接口 - 專用 4-20mA 2Wire Trsmtr ’Smart’ Prog RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59
XTR108EA/2K5G4 功能描述:接口 - 專用 4-20mA 2Wire Trsmtr ’Smart’ Prog RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59
XTR108EA-2K5 制造商:BB 制造商全稱:BB 功能描述:4-20mA, TWO-WIRE TRANSMITTER a??Smarta?? Programmable with Signal Conditioning
XTR108EA-2K5G4 制造商:BB 制造商全稱:BB 功能描述:4-20mA, TWO-WIRE TRANSMITTER a??Smarta?? Programmable with Signal Conditioning
XTR108EAG4 功能描述:接口 - 專用 4-20mA 2Wire Trsmtr ’Smart’ Prog RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59
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