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부품번호 | XTR104 기능 |
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기능 | 4-20mA Current Transmitter with BRIDGE EXCITATION AND LINEARIZATION | ||
제조업체 | Burr-Brown Corporation | ||
로고 | |||
전체 11 페이지수
® XTR104
4-20mA Current Transmitter with
BRIDGE EXCITATION AND LINEARIZATION
FEATURES
q LESS THAN ±1% TOTAL ADJUSTED
ERROR, –40°C TO +85°C
q BRIDGE EXCITATION AND LINEARIZATION
q WIDE SUPPLY RANGE: 9V to 40V
q LOW SPAN DRIFT: 50ppm/°C max
q HIGH PSR: 110dB min
q HIGH CMR: 80dB min
DESCRIPTION
The XTR104 is a monolithic 4-20mA, two-wire cur-
rent transmitter integrated circuit designed for bridge
input signals. It provides complete bridge excitation,
instrumentation amplifier, linearization, and current
output circuitry necessary for high impedance strain
gage sensors.
The instrumentation amplifier can be used over a wide
range of gain, accommodating a variety of input signals
and sensors. Total adjusted error of the complete current
transmitter, including the linearized bridge is less than
±1% over the full –40°C to +85°C temperature range.
This includes zero drift, span drift and non-linearity for
bridge outputs as low as 10mV. The XTR104 operates
on loop power supply voltages down to 9V.
Linearization circuitry consists of a second, fully inde-
pendent instrumentation amplifier that controls the bridge
excitation voltage. It provides second-order correction
to the transfer function, typically achieving a 20:1
improvement in nonlinearity, even with low cost trans-
ducers.
The XTR104 is available in 16-pin plastic DIP and
SOL-16 surface-mount packages specified for the
–40°C to +85°C temperature range.
APPLICATIONS
q INDUSTRIAL PROCESS CONTROL
q FACTORY AUTOMATION
q SCADA
q WEIGHTING SYSTEMS
q ACCELEROMETERS
BRIDGE NONLINEARITY CORRECTION
USING XTR104
2.0
Uncorrected
Bridge Output
1.5
1.0
0.5
0
–0.5
0mV
Corrected
5mV
Bridge Output
10mV
R LIN
+ 9V to 40V
VPS
RG XTR104
–
4-20 mA
VO
RL
International Airport Industrial Park • Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1992 Burr-Brown Corporation
PDS1-1146B
XTR104Printed in U.S.A. September, 1993
®
DICE INFORMATION
FPO
XTR104 DIE TOPOGRAPHY
PAD
1
2
3
4
5
6
7
8
FUNCTION
V+IN
V–IN
V+LIN
V–LIN
RG
RG
IO
RLIN
PAD
9
10
11
12A, 12B
13
14
15
16
FUNCTION
RLIN
V+
E (Emitter)
VREF
B (Base)
Zero Adj.
Zero Adj.
Zero Adj.
Pads 12A and 12B must be connected.
NC: No Connection
Substrate Bias: Internally connected to the IO terminal
(#7).
MECHANICAL INFORMATION
Die Size
Die Thickness
Min. Pad Size
Backing
MILS (0.001")
168 x 104 ±5
20 ±3
4x4
MILLIMETERS
4.27 x 2.64 ±0.13
0.51 ±0.08
0.1 x 0.1
None
TYPICAL PERFORMANCE CURVES
T
A
=
+25°C,
V+
=
24V,
unless
otherwise
noted.
TRANSCONDUCTANCE vs FREQUENCY
80
60 RG = 25Ω
RG = 100Ω
40 RG = 400Ω
RG = 2kΩ
20 RG = ∞
0
100
1k 10k 100k
Frequency (Hz)
1M
20mA
4mA
STEP RESPONSE
R
G
=
∞
RG = 25Ω
100µs/Div
®
XTR104
4
4페이지 BRIDGE BALANCE
Figure 1 shows a bridge trim circuit (R1, R2). This adjust-
ment can be used to compensate for the initial accuracy of
the bridge and/or to trim the offset voltage of the XTR104.
The values of R1 and R2 depend on the impedance of the
bridge, and the trim range required. This trim circuit places
an additional load on the VR output. The effective load of the
trim circuit is nearly equal to R2. Total load on the VR output
terminal must not exceed 2mA. An approximate value for R1
can be calculated:
5V • R
R≈
B
1 4•V
TRIM
(3)
Where: RB is the resistance of the bridge.
VTRIM is the desired ±voltage trim range (in V).
Make R2 equal or lower in value to R1.
Figure 2 shows another way to adjust zero errors using the
output current adjustment pins of the XTR104. This pro-
vides ±500µA (typical) adjustment around the initial low-
scale output current. This is an output current adjustment
that is independent of the input stage gain set with RG. If the
input stage is set for high gain the output current adjustment
may not provide sufficient range.
XTR104
(a)
With V+LIN and V–LIN connected to the bridge output, the
bridge excitation voltage can be made to vary as much as
±0.5V in response to the bridge output voltage. Be sure that
the total load on the VR output is less than 2mA at the
maximum excitation voltage, VR = 5.5V.
Signal-dependent variation of the bridge excitation voltage
provides a second-order term to the complete transfer func-
tion (including the bridge). This can be tailored to correct for
bridge sensor nonlinearity. Either polarity of nonlinearity
(bowing up or down) can be compensated by proper connec-
tion of the VLIN inputs. Connecting V+LIN to V+IN and V–LIN
to V–IN (Figure 1) causes VR to increase with bridge output
which compensates for a positive bow in the bridge re-
sponse. Reversing the connections (Figure 3) causes VR to
decrease with increasing bridge output, to compensate for
negative-bowing nonlinearity.
To determine the required value for RLIN you must know the
nonlinearity of the bridge sensor with constant excitation
voltage. The linearization circuitry can only compensate for
the parabolic portion of a sensor’s nonlinearity. Parabolic
nonlinearity has a maximum deviation from linear occurring
at mid-scale (see Figure 4). Sensors with nonlinearity curves
similar to that shown in Figure 4, but not peaking exactly at
mid-scale can be substantially improved. A nonlinearity that
is perfectly “S-shaped” (equal positive and negative
nonlinearity) cannot be corrected with the XTR104. It may,
however, be possible to improve the worst-case nonlinearity
of a sensor by equalizing the positive and negative
nonlinearity.
15
16
10kΩ
14
±500µA typical
output current
adjustment range.
The nonlinearity, B (in % of full scale), is positive or
negative depending on the direction of the bow. A maximum
of ±2.5% nonlinearity can be corrected. An approximate
value for RLIN can be calculated by:
K •V
R = LIN
FS
LIN 0 . 2 • B
(5)
XTR104
15
16
5kΩ
(b)
14
5kΩ ±50µA typical
output current
adjustment range.
FIGURE 2. Low-scale Output Current Adjustment.
LINEARIZATION
Differential voltage applied to the linearization inputs, V+LIN
and V–LIN, causes the reference (excitation) voltage, VR, to
vary according to the following equation:
Where: KLIN ≈ 24000.
VFS is the full-scale bridge output (in Volts) with
constant 5V excitation.
B is the parabolic nonlinearity in ±% of full scale.
RLIN in Ω.
Methods for refining this calculation involve determining
the actual value of KLIN for a particular device (explained
later).
B is a signed number (negative for a downward-bowing
nonlinearity). This can produce a negative value for RLIN. In
this case, use the resistor value indicated (ignore the sign),
but connect V+LIN to V–IN and V–LIN to V+IN as shown in
Figure 3.
V = 5V + V
R LIN
K
LIN
R
LIN
(4)
Where: VLIN is the voltage applied to the V+LIN and V–LIN
differential inputs (in V).
RLIN in Ω.
KLIN ≈ 24000 (approximately ±20% depending on
variations in the fabrication of the XTR104).
This approximate calculation of RLIN generally provides
about a 5:1 improvement in bridge nonlinearity.
Example: The bridge sensor depicted by the negative-
bowing curve in Figure 4. Its full scale output is 10mV with
constant 5V excitation. Its maximum nonlinearity, B, is
–1.9% referred to full scale (occurring at mid-scale). Using
equation 5:
®
7 XTR104
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부품번호 | 상세설명 및 기능 | 제조사 |
XTR101 | Precision/ Low Drift 4-20mA TWO-WIRE TRANSMITTER | Burr-Brown Corporation |
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DataSheet.kr | 2020 | 연락처 | 링크모음 | 검색 | 사이트맵 |