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參數(shù)資料
| 型號： | XTR114U |
| 英文描述： | 4-20mA CURRENT TRANSMITTERS with Sensor Excitation and Linearization |
| 中文描述： | 的4 - 20mA的傳感器激勵和線性電流遞質(zhì) |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 255K |
| 代理商： | XTR114U |
12
XTR112, XTR114
A typical two-wire RTD application with linearization is
shown in Figure 1. Resistor R
LIN1
provides positive feed-
back and controls linearity correction. R
LIN1
is chosen ac-
cording to the desired temperature range. An equation is
given in Figure 1.
In three-wire RTD connections, an additional resistor, R
LIN2
,
is required. As with the two-wire RTD application, R
LIN1
provides positive feedback for linearization. R
LIN2
provides
an offset canceling current to compensate for wiring resis-
tance encountered in remotely located RTDs. R
LIN1
and R
LIN2
are chosen such that their currents are equal. This makes the
voltage drop in the wiring resistance to the RTD a common-
mode signal which is rejected by the XTR112 and XTR114.
The nearest standard 1% resistor values for R
LIN1
and R
LIN2
should be adequate for most applications. Tables II and III
provide the 1% resistor values for a three-wire Pt1000 RTD
connection.
If no linearity correction is desired, the V
LIN
pin should be
left open. With no linearization, R
G
= 2500 V
FS
, where
V
FS
= full-scale input range.
RTDs
The text and figures thus far have assumed a Pt1000 RTD.
With higher resistance RTDs, the temperature range and
input voltage variation should be evaluated to ensure proper
common-mode biasing of the inputs. As mentioned earlier,
R
CM
can be adjusted to provide an additional voltage drop to
bias the inputs of the XTR112 and XTR114 within their
common-mode input range.
ERROR ANALYSIS
Table IV shows how to calculate the effect various error
sources have on circuit accuracy. A sample error calculation
for a typical RTD measurement circuit (Pt1000 RTD, 200
°
C
measurement span) is provided. The results reveal the
XTR112’s and XTR114’s excellent accuracy, in this case 1%
unadjusted for the XTR112, 1.16% for the XTR114. Adjusting
resistors R
G
and R
Z
for gain and offset errors improves the
XTR112’s accuracy to 0.28% (0.31% for the XTR114). Note
that these are worst-case errors; guaranteed maximum values
were used in the calculations and all errors were assumed to be
positive (additive). The XTR112 and XTR114 achieve perfor-
mance which is difficult to obtain with discrete circuitry and
requires less space.
OPEN-CIRCUIT PROTECTION
The optional transistor Q
2
in Figure 3 provides predictable
behavior with open-circuit RTD connections. It assures that if
any one of the three RTD connections is broken, the XTR’s
output current will go to either its high current limit (
≈
27mA)
or low current limit (
≈
1.3mA for XTR112 and
≈
1mA for
XTR114). This is easily detected as an out-of-range condition.
FIGURE 3. Three-Wire Connection for Remotely Located RTDs.
I
O
I
O
XTR112
XTR114
OPEN RTD
TERMINAL
1
2
3
≈
1.3mA
≈
27mA
≈
1.3mA
≈
1mA
≈
27mA
≈
1mA
RTD
(R
LINE2
)
(R
LINE1
)
R
Z(1)
R
LIN2(1)
R
LIN1(1)
(R
LINE3
)
2
1
3
0.01
μ
F
R
CM
0.01
μ
F
Q
2(2)
2N2222
NOTES: (1) See Table I for resistor equations and
1% values. (2) Q
optional. Provides predictable
output current if any one RTD connection is
broken:
13
4
3
2
R
G
XTR112
XTR114
7
6
(1)
R
G
R
G
V
IN
–
V
IN
+
V
LIN
I
R1
I
R2
V
REG
V+
I
RET
I
O
E
B
8
9
Q
1
I
O
I
O
14
11
12
1
10
EQUAL line resistances here
creates a small common-mode
voltage which is rejected by
XTR112
and
XTR114
.
Resistance in this line causes
a small common-mode voltage
which is rejected by
XTR112
and
XTR114.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| XTR114U/2K5 | 功能描述:IC 4-20MA I-TRANSMITTER 14-SOIC RoHS:是 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關文件:Automotive Product Guide 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數(shù)字 輸出類型:數(shù)字 接口:JTAG，串行 電流 - 電源:100µA 安裝類型:表面貼裝 封裝/外殼:20-TSSOP（0.173"，4.40mm 寬） 供應商設備封裝:20-TSSOP 包裝:管件 |
| XTR114UA | 功能描述:電流靈敏放大器 4-20mA Crnt Trnsmtr w/Sensor Exc & Lin RoHS:否 制造商:Texas Instruments 通道數(shù)量: 共模抑制比（最小值）:110 dB 輸入補償電壓:80 uV 電源電壓-最大:5.5 V 電源電壓-最小:2.7 V 電源電流:350 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
| XTR114UA/2K5 | 功能描述:IC 4-20MA I-TRANSMITTER 14-SOIC RoHS:是 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關文件:Automotive Product Guide 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數(shù)字 輸出類型:數(shù)字 接口:JTAG，串行 電流 - 電源:100µA 安裝類型:表面貼裝 封裝/外殼:20-TSSOP（0.173"，4.40mm 寬） 供應商設備封裝:20-TSSOP 包裝:管件 |
| XTR114UA/2K5E4 | 功能描述:電流靈敏放大器 4-20mA Crnt Trnsmtr w/Sensor Exc & Lin RoHS:否 制造商:Texas Instruments 通道數(shù)量: 共模抑制比（最小值）:110 dB 輸入補償電壓:80 uV 電源電壓-最大:5.5 V 電源電壓-最小:2.7 V 電源電流:350 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
| XTR114UAE4 | 功能描述:電流靈敏放大器 4-20mA Crnt Trnsmtr w/Sensor Exc & Lin RoHS:否 制造商:Texas Instruments 通道數(shù)量: 共模抑制比（最小值）:110 dB 輸入補償電壓:80 uV 電源電壓-最大:5.5 V 電源電壓-最小:2.7 V 電源電流:350 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
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