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XTR101AG 参数 Datasheet PDF下载

XTR101AG图片预览
型号: XTR101AG
PDF下载: 下载PDF文件 查看货源
内容描述: 高精度,低漂移的4-20mA两线制变送器 [Precision, Low Drift 4-20mA TWO-WIRE TRANSMITTER]
分类和应用:
文件页数/大小: 15 页 / 197 K
品牌: BB [ BURR-BROWN CORPORATION ]
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8. Consider PC board layout which minimizes parasitic  
capacitance, especially in high gain.  
Figure 6 shows a similar connection for a resistive trans-  
ducer. The transducer could be excited either by one (as  
shown) or both current sources. Also, the offset adjustment  
has higher resolution compared to Figure 5.  
SELECTING RS  
RSPAN is chosen to that a given full scale input span eINFS  
CMV AND CMR  
will result in the desired full scale output span of IOFS  
,
The XTR101 is designed to operate with a nominal 5V  
common-mode voltage at the input and will function prop-  
erly with either input operating over the range of 4V to 6V  
with respect to pin 7. The error caused by the 5V CMV is  
already included in the accuracy specifications.  
[(0.016 ) + (40/RS)] eIN = IO = 16mA.  
Solving for RS:  
40  
RS =  
(1)  
IO/eIN – 0.016  
If the inputs are biased at some other CMV then an input  
offset error term is (CMV – 5)/CMRR; CMR is in dB,  
CMRR is in V/V.  
For example, if eINFS = 100mV for IOFS = 16mA,  
40  
40  
RS =  
=
=
16mA/100mV) – 0.016  
0.16 – 0.016  
SIGNAL SUPPRESSION AND ELEVATION  
40  
In some applications it is desired to have suppressed zero  
range (input signal elevation) or elevated zero range (input  
signal suppression). This is easily accomplished with the  
XTR101 by using the current sources to create the suppres-  
sion/elevation voltage. The basic concept is shown in Fig-  
ures 7 and 8(a). In this example the sensor voltage is derived  
from RT (a thermistor, RTD, or other variable resistance  
element) excited by one of the 1mA current sources. The  
other current source is used to create the elevated zero range  
voltage. Figures 8(b), (c) and (d) show some of the possible  
circuit variations. These circuits have the desirable feature  
of noninteractive span and suppression/elevation adjust-  
ments. Note: It is not recommended to use the optional offset  
voltage null (pins 1, 2 and 14) for elevation/suppression.  
This trim capability is used only to null the amplifier’s input  
offset voltage. In many applications the already low offset  
voltage (typically 20µV) will not need to be nulled at all.  
Adjusting the offset voltage to nonzero values will disturb  
the voltage drift by ±0.3µV/°C per 100µV or induced offset.  
= 278Ω  
0.144  
See Typical Performance Curves for a plot of RS vs eINFS  
.
Note that in order not to exceed the 20mA upper range limit,  
eIN must be less than 1V when RS = and proportionately  
smaller as RS decreases.  
BIASING THE INPUTS  
Because the XTR operates from a single supply both e1 and  
e2 must be biased approximately 5V above the voltage at pin  
7 to assure linear response. This is easily done by using one  
or both current sources and an external resistor R2. Figure 5  
shows the simplest case— a floating voltage source e'2. The  
2mA from the current sources flows through the 2.5kΩ  
value of R2 and both e1 and e2 are raised by the required 5V  
with respect to pin 7. For linear operation the constraint is  
+4V e1 +6V  
+4V e2 +6V  
The offset adjustment is used to remove the offset voltage of  
the input amplifier. When the input differential voltage (eIN)  
equals zero, adjust for 4mA output.  
D1  
11  
e1  
3
5
10  
8
1mA 1mA  
11  
D1  
10  
e1  
3
5
+
eIN  
RS  
8
XTR101  
0.01µF  
6
+
+
24V  
RL  
eL  
4-20 mA  
eIN  
+
RS  
2mA  
4
7
XTR101  
Adj.  
6
+
14  
2
e2  
0.01µF  
+
+
24V  
RL  
+
100kΩ  
1
Offset  
Adjust  
eL  
e2  
RT  
1MΩ  
7
e2  
R2  
14  
+
1
2
4
2.5kΩ  
1MΩ  
+
IO  
40  
RS  
e'2  
IO = 4mA + (0.016  
+
)eIN  
2mA  
+5V  
Offset  
Adjust  
0.01µF  
Alternate circuitry  
shown in Figure 8.  
eIN = e'2 = 1mA X RT  
R2  
2.5kΩ  
40  
RS  
0.01µF  
IO = 4mA + (0.016  
IN = e2  
+
)eIN  
e
2mA  
+5V  
FIGURE 6. Basic Connection for Resistive Source.  
FIGURE 5. Basic Connection for Floating Voltage Source.  
®
XTR101  
8