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Número de pieza | XTR106 | |
Descripción | 4-20mA CURRENT TRANSMITTER with Bridge Excitation and Linearization | |
Fabricantes | Burr-Brown Corporation | |
Logotipo | ||
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No Preview Available ! ® XTR106
XTR106
XTR106
4-20mA CURRENT TRANSMITTER
with Bridge Excitation and Linearization
FEATURES
q LOW TOTAL UNADJUSTED ERROR
q 2.5V, 5V BRIDGE EXCITATION REFERENCE
q 5.1V REGULATOR OUTPUT
q LOW SPAN DRIFT: ±25ppm/°C max
q LOW OFFSET DRIFT: 0.25µV/°C
q HIGH PSR: 110dB min
q HIGH CMR: 86dB min
q WIDE SUPPLY RANGE: 7.5V to 36V
q 14-PIN DIP AND SO-14 SURFACE-MOUNT
DESCRIPTION
The XTR106 is a low cost, monolithic 4-20mA, two-
wire current transmitter designed for bridge sensors. It
provides complete bridge excitation (2.5V or 5V refer-
ence), instrumentation amplifier, sensor linearization,
and current output circuitry. Current for powering ad-
ditional external input circuitry is available from the
VREG pin.
The instrumentation amplifier can be used over a wide
range of gain, accommodating a variety of input signal
types and sensors. Total unadjusted error of the com-
plete current transmitter, including the linearized bridge,
is low enough to permit use without adjustment in many
applications. The XTR106 operates on loop power sup-
ply voltages down to 7.5V.
Linearization circuitry provides second-order correction
to the transfer function by controlling bridge excitation
voltage. It provides up to a 20:1 improvement in
nonlinearity, even with low cost transducers.
The XTR106 is available in 14-pin plastic DIP and
SO-14 surface-mount packages and is specified for the
–40°C to +85°C temperature range. Operation is from
–55°C to +125°C.
APPLICATIONS
q PRESSURE BRIDGE TRANSMITTER
q STRAIN GAGE TRANSMITTER
q TEMPERATURE BRIDGE TRANSMITTER
q INDUSTRIAL PROCESS CONTROL
q SCADA REMOTE DATA ACQUISITION
q REMOTE TRANSDUCERS
q WEIGHING SYSTEMS
q ACCELEROMETERS
BRIDGE NONLINEARITY CORRECTION
USING XTR106
2.0
Uncorrected
Bridge Output
1.5
1.0
0.5
Corrected
0
–0.5
0mV
5mV
Bridge Output
10mV
VREF5
VREG (5.1V)
VREF 2.5V
RLIN
+ 7.5V to 36V
VPS
4-20mA
5V RG XTR106
VO
RL
–
IRET
Lin
Polarity
IOUT
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
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1998 Burr-Brown Corporation
PDS-1449A
Printed in U.S.A. June, 1998
1 page TYPICAL PERFORMANCE CURVES
At TA = +25°C, V+ = 24V, unless otherwise noted.
TRANSCONDUCTANCE vs FREQUENCY
60
50 RG = 50Ω
40
CCOOUUTT==00.0.011µµFF
COUT = 0.033µF
COUT connected
between V+ and IO
30 RG = 1kΩ
20
10
RL = 250Ω
0
100
1k
10k
Frequency (Hz)
100k
1M
20mA
STEP RESPONSE
RG = 1kΩ
COUT = 0.01µF
RG = 50Ω
4mA
50µs/div
110
100
90
80
70
60
50
40
30
10
COMMON-MODE REJECTION vs FREQUENCY
RG = 1kΩ
RG = 50Ω
100 1k
10k 100k
Frequency (Hz)
1M
INPUT OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
90
Typical production
80 distribution of
70 packaged units.
60
50
40
30
20
10
0
Offset Voltage Drift (µV/°C)
POWER SUPPLY REJECTION vs FREQUENCY
160
140 RG = 50Ω
COUT = 0
120
100 RG = 1kΩ
80
60
40
20
0
10
100 1k
10k 100k 1M
Frequency (Hz)
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–2.5
–1.0
INPUT OFFSET VOLTAGE CHANGE
vs VREG and VREF CURRENTS
VOS vs IREG
VOS vs IREF
–0.5
0 0.5 1.0 1.5 2.0
Current (mA)
2.5
®
5 XTR106
5 Page Figure 4, but not peaking exactly at mid-scale can be
substantially improved. A sensor with a “S-shaped”
nonlinearity curve (equal positive and negative nonlinearity)
cannot be improved with the XTR106’s correction circuitry.
The value of RLIN is chosen according to Equation 4 shown
in Figure 3. RLIN is dependent on a linearization factor,
KLIN, which differs for the 2.5V reference and 5V reference.
The sensor’s nonlinearity term, B (relative to full scale), is
positive or negative depending on the direction of the bow.
A maximum ±5% non-linearity can be corrected when the
5V reference is used. Sensor nonlinearity of +5%/–2.5% can
be corrected with 2.5V excitation. The trim circuit shown in
Figure 3d can be used for bridges with unknown bridge
nonlinearity polarity.
Gain is affected by the varying excitation voltage used to
correct bridge nonlinearity. The corrected value of the gain
resistor is calculated from Equation 5 given in Figure 3.
VREF5
VREG
VREF2.5
5V
R1
R2 + –
14
13
RLIN
5+
1
11
4
RG XTR106
3
2–
6
IRET
12 Lin
Polarity
3a. Connection for Positive Bridge Nonlinearity, VREF = 5V
VREF2.5
VREG
2.5V
VREF5
14
13
RLIN
5+
1
11
4
R1
R2 + –
RG XTR106
3
2–
IRET
6
12 Lin
Polarity
3b. Connection for Negative Bridge Nonlinearity, VREF = 2.5V
VREF5
VREG
VREF2.5
14
13
RLIN
5+
1
11
5V 4
R1
R2 + –
RG XTR106
3
2–
IRET
6
12 Lin
Polarity
3c. Connection if no linearity correction is desired, VREF = 5V
XTR106
IRET
6
Lin
Polarity
12
VREG
1
RX
100kΩ
RY
15kΩ
Open RX for negative bridge nonlinearity
Open RY for positive bridge nonlinearity
3d. On-Board Resistor Circuit for Unknown Bridge Nonlinearity Polarity
EQUATIONS
Linearization Resistor:
RLIN =
KLIN
•
4B
1– 2B
(in Ω)
(4)
Gain-Set Resistor:
RG
=
VFS
400µA
• 1 + 2B
1 – 2B
(in Ω)
(5)
Adjusted Excitation Voltage at Full-Scale Output:
VREF (Adj)
=
VREF (Initial) •
1 + 2B
1 – 2B
(in V)
(6)
where, KLIN is the linearization factor (in Ω)
KLIN = 9905Ω for the 2.5V reference
KLIN = 6645Ω for the 5V reference
B is the sensor nonlinearity relative to VFS
(for –2.5% nonlinearity, B = –0.025)
VFS is the full-scale bridge output without
linearization (in V)
Example:
Calculate RLIN and the resulting RG for a bridge sensor with
2.5% downward bow nonlinearity relative to VFS and determine
if the input common-mode range is valid.
VREF = 2.5V and VFS = 50mV
For a 2.5% downward bow, B = –0.025
(Lin Polarity pin connected to VREG)
For VREF = 2.5V, KLIN = 9905Ω
RLIN =
(9905Ω) (4) ( –0.025)
1 – (2) ( –0.025)
= 943Ω
RG =
0.05V • 1 + (2) ( –0.025) = 113Ω
400µA 1 – (2) ( –0.025)
VCM
=
VREF (Adj)
2
=
1
2
• 2.5V •
1 + (2) ( –0.025)
1 – (2) ( –0.025)
= 1.13V
which falls within the 1.1V to 3.5V input common-mode range.
FIGURE 3. Connections and Equations to Correct Positive and Negative Bridge Nonlinearity.
11 XTR106
®
11 Page |
Páginas | Total 15 Páginas | |
PDF Descargar | [ Datasheet XTR106.PDF ] |
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