廬
APPLICATION BULLETIN
By R. Mark Stitt and David Kunst (602) 746-7445
Mailing Address: PO Box 11400 鈥?Tucson, AZ 85734 鈥?Street Address: 6730 S. Tucson Blvd. 鈥?Tucson, AZ 85706
Tel: (602) 746-1111 鈥?Twx: 910-952-111 鈥?Telex: 066-6491 鈥?FAX (602) 889-1510 鈥?Immediate Product Info: (800) 548-6132
SINGLE SUPPLY 4-20mA CURRENT LOOP RECEIVER
Many industrial current-loop data acquisition systems oper-
ate on a 24V or 28V single supply. You can make a single-
supply current loop receiver with the RCV420 by using its
10V reference as a pseudo ground. The RCV420 will con-
vert a 4-20mA loop current into a 0 to 5V output voltage
with no external components required. The current loop can
be sourcing or sinking and can be referenced to either the
power-supply V+ or ground.
The complete circuit for a single-supply current loop re-
ceiver is shown in Figure 1. In this application, a 4-20mA
current source referenced to power-supply ground drives the
receiver. The
V鈥?/div>
terminal and the
Ref Com
terminal of the
RCV420 are both tied to power supply ground. The 10V
reference output (Ref
Out)
becomes a pseudo ground where
the current loop receiver common pin (Rcv
Com)
is tied. The
current loop receiver output is now referenced to the 10V
pseudo ground.
In normal operation, the 4-20mA current loop signal would
produce a 0-5V output with the RCV420 offset pin (Ref
In)
connected to the +10V reference. The 10V reference pro-
vides a 鈥?.25V offset so 4mA input current will produce 0V
out. In this application, the
Ref In
pin is connected to power
supply ground which acts as a 鈥?0V reference鈥攑roducing
a +1.25V offset. Now with the inputs connected for an
4-20mA
Input from
Current Loop
inverted output signal, the RCV420 output will be 0 to 鈥?V
referenced to the pseudo ground. Since the pseudo ground is
at 10V, the actual output will be 10V to 5V鈥攁 signal which
can drive most floating ground meters.
For a current loop receiver with a 4-20mA current sink
referenced to the power-supply V+, use the connection
shown in Figure 2.
The circuit can operate on a single supply ranging from
+15V to +36V (+44V absolute max). The pseudo ground
(Ref
Out)
can source or sink up to 5mA.
For an isolated single-supply 4-20mA current loop receiver,
you can connect the circuit to an isolation amplifier as
shown in Figure 3. In this circuit the ISO122 is operated
single-supply using the 10.0V pseudo ground. Note that the
output side of the isolation amplifier still requires dual
supplies.
Output from the ISO122 will be 0 to 鈥?V. You could
interchange the input connections to the ISO122 to get a 0
to 5V output, but power-supply rejection would degrade
performance.
The ISO122 is a low-cost iso amp in a standard plastic DIP.
For a hermetic isolation amplifier, use the ISO120. Hook-up
details are shown in Application Bulletin AB-009.
+28V
(15V to 36V)
V+ 16
300k鈩?/div>
99k鈩?/div>
RCV420
Ref
92k鈩?/div>
In
12
Rcv
11.5k鈩?/div>
FB
15
Ref
Out
14
1.01k鈩?/div>
300k鈩?/div>
100k鈩?/div>
10.0V
Ref
Ref
FB
10
Ref
Out
11
10.0V to
5.0V
1
鈥揑n
75鈩?/div>
2
CT
75鈩?/div>
NC
(1)
LO
0 to 5V
Meter
HI
3
+In
10.0V
Pseudo
Ground
V鈥?4
Rcv 13
Com
Ref 5
Com
NOTE: (1) NC = No Connection.
FIGURE 1.
漏
1992 Burr-Brown Corporation
AB-041
Printed in U.S.A. June, 1992
AB-041相關(guān)型號PDF文件下載
-
型號
版本
描述
廠商
下載
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英文版
AB-001 - INCREASING INA117 DIFFERENTIAL INPUT RANGE
ETC
-
英文版
AB-002 - MAKE A PRECISION CURRENT SOURCE OR CURRENT SINK
ETC
-
英文版
AB-003 - VOLTAGE-REFERENCE FILTERS
ETC
-
英文版
AB-004 - MAKE A PRECISION -10V REFERENCE
ETC
-
英文版
AB-005 - Make A Precision -10V Reference
ETC
-
英文版
AB-006 - Make a -10V to +10V Adjustable Precision Voltage So...
ETC
-
英文版
AB-007 - CLASSICAL OP AMP OR CURRENT-FEEDBACK OP AMP?
ETC
-
英文版
AB-008 - AC COUPLING INSTRUMENTATION AND DIFFERENCE AMPLIFIE...
ETC
-
英文版
AB-009 - SINGLE-SUPPLY OPERATION OF ISOLATION AMPLIFIERS
ETC
-
英文版
AB-010 - -200V DIFFERENCE AMPLIFIER WITH COMMON-MODE VOLTAGE...
ETC
-
英文版
AB-011 - LOW POWER SUPPLY VOLTAGE OPERATION OF REF102 10.0V ...
ETC
-
英文版
AB-012 - BOOST ISO120 BANDWIDTH TO MORE THAN 100kHz
ETC
-
英文版
AB-013 - INCREASING ADC603 INPUT RANGE
ETC
-
英文版
AB-014 - INPUT OVERLOAD PROTECTION FOR THE RCV420 4-20mA CUR...
ETC
-
英文版
AB-015 - EXTENDING THE COMMON-MODE RANGE OF DIFFERENCE AMPLI...
ETC
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英文版
AB-016 - BOOST AMPLIFIER OUTPUT SWING WITH SIMPLE MODIFICATI...
ETC
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英文版
AB-017 - Sallen-Key Low-Pass Filter Design Program
ETC
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英文版
AB-018 - 0 TO 20mA RECEIVER USING RCV420
ETC
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英文版
AB-019 - USING THE ADS7800 12 BIT ADC WITH UNIPOLAR INPUT SI...
ETC
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英文版
AB-020 - BURR-BROWN SPICE BASED MACROMODELS. REV. F
ETC
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