Post on 27-Jan-2021
transcript
Current Loop Transmitter Configurations TI Precision Labs – Current Loop Transmitters
Presented by Katlynne Jones
Prepared by Katlynne Jones
1
Transmitter configurations
2
Transmitter
+
_
+
_
Receiver
Power
supply
Supply &
Signal Current
VLOOP
1
2
+
_
Power
supply
+
_
Receiver
Transmitter
Supply
Current
Signal
Current
1
2
3
4
2-wire block diagram 3-wire block diagram 4-wire block diagram
+
_
Power
supply
+
_
Receiver
Transmitter
Supply
Current
Signal
Current
1
2
3
2
Transmitter
RIn
VIn
IRET
IIN
IOUT
V+
+
_+
_
+
_Receiver
Power
supply
Supply &
Signal Current
VLOOP
Sensor + Input
Circuitry
VOUT
GND
V+ VREG
2-wire transmitter
• 2-wire transmitter
block diagram
– 2 wires create a
loop that transmits
the signal current
and transmitter
power
– IRET cannot be
grounded to VLOOP!
– Transmitter,
sensor, and input
circuitry must
consume
Transmitter
+
_
Power
supply
VIN
GND
V+
IOUT
Supply
Current
VIn
+
_
Sensor + Input
Circuitry
VOUT
GND
Signal
Current
+
_
Receiver
4
3-wire transmitter
• 3-wire transmitter
block diagram
– 3 wires create
separate loops for
the signal current
and transmitter
power
– Transmitter ground
is shared with the
receiver
– Can use 0-20mA,
or 0-24mA ranges
as well
Transmitter
+
_
Power
supply
Signal
Current
+
_
Receiver
Supply
Current
VIN
GNDV+
IOUT+
IOUT-VIn
+
_
Sensor + Input
Circuitry
VOUT
GNDGND
5
4-wire transmitter
• 4-wire transmitter
block diagram
– 4 wires create
separate loops for
the signal current
and transmitter
power
– Can use 0-20mA,
or 0-24mA ranges
as well
– Additional isolation
schemes
4-wire transmitter power isolated application
6
Receiver
VIN
IOUT+
IOUT-
+_
IN+
IN-
RSENSE
Transmitter
REF
ADC
Receiver
SupplyTransmitter
Supply
24V+
-
Ref
+
INA333RG10kΩ
+_
REF+
+
-
Current
LimiterREG
5V
RSET
REG
5V
Sensor
OPA333
4-wire transmitter fully isolated application
7
Receiver
VIN
IOUT+
IOUT-
+_
IN+
IN-
RSENSE
Transmitter
ADC
Receiver
SupplyTransmitter
Supply
24V +_
++
-
Current
LimiterREG
5V
RSET
REG
5V
VCC1
INA
INB
INC
GND1
MCU
ADC+
ADC-
CS
SCLK
SDO
REG
V+
GND
VCC2
OUTA
OUTB
OUTC
GND2
DAC
/CS
SCLK
SDO
V+
GND
VOUT
VREF
Sensor
ISO7330
REF
5V2.5V
Sensor
Transmitter
+
_
Power
supply
VIN
GND
V+
IOUT
Supply
Current
VIn
+
_
Sensor + Input
Circuitry
VOUT
GND
Signal
Current
+
_
Receiver
Transmitter
RIn
VIn
IRET
IIN
IOUT
V+
+
_
+
_
+
_Receiver
Power
supply
Supply &
Signal Current
VLOOP
Sensor + Input
Circuitry
VOUT
GND
V+ VREG
2-wire vs. 3-wire transmitters
2-Wire transmitter 3-Wire transmitter
8
Typical 4-20mA applications
°T
3-Wire
Transmitter
2-Wire
Transmitter
RVLOOP
– Temperature, humidity, ambient light
– 2-wire transmitter
– Valve, actuator, heater
– 3-wire transmitter
Transmit control
signals from a
control station out to
a remote device.
Report a process
variable from a
remote sensor to a
control station.
9
Transmitter
RIn
VIn
IRET
IIN
IOUT
V+
+
_
+
_+
_Receiver
Power
supply
Supply &
Signal Current
VLOOP
Sensor + Input
Circuitry
VOUT
GND
V+ VREG
°T
3-Wire
Transmitter
2-Wire
Transmitter
RVLOOP
Why use 2-wire
10
Report a process
variable from a
remote sensor to a
control station.
Why use 3-wire
11
Transmit control
signals from a
control station out to
a remote device.
3-wire
Transmitter
+
_
Power
supply
VIN
GND
V+
IOUT
Power
Current
VIn
+
_
Sensor + Input
Circuitry
VOUT
GND
Signal
Current
+
_
Receiver
°T
3-Wire
Transmitter
2-Wire
Transmitter
RVLOOP
Tradeoffs
• Cost
– 2-wire tends to be lower cost. 3-wire requires a third cable and if
locally powered, requires an additional supply.
• Design
– More considerations in designing a 2-wire transmitter when supplying
the driving circuitry from the transmitter.
• 4mA current budget
• Must not connect IRET to VLOOP ground
– Cannot connect multiple 2-wire transmitters to sensors or DACs with
multiple outputs.
Show slide where
you can add the
isolation to
connect multiple
2-wire
transmitters in two
wire video
12
+ _
Power
supply
VLOOP
+ _
Receiver
+ _
Receiver
2- wire
Transmitter
(XTR116)
RIn
VIn
IRET
IIN
IOUT
V++
_
Sensor + Input
Circuitry
VOUT
GND
2- wire
Transmitter
(XTR116)
RIn
VIn
IRET
IIN
IOUT
V++
_
Sensor + Input
Circuitry
VOUT
GND
2- wire
Transmitter
(XTR116)
RIn
VIn
IRET
IIN
IOUT
V++
_
Sensor + Input
Circuitry
VOUT
GND + _
Receiver...
...V+ VREG
V+ VREG
V+ VREG
Tradeoffs cont.
13
+ _
Receiver
+ _
Receiver
+ _
Power
supply
VLOOP
2- wire
Transmitter
(XTR116)
RIn
IRET
IIN
IOUT
V+
2- wire
Transmitter
(XTR116)
RIn
IRET
IIN
IOUT
V+
2- wire
Transmitter
(XTR116)
RIn
IRET
IIN
IOUT
V+
+ _
Receiver...
...
DAC
VOUT_1
VOUT_2
VOUT_N
...
VREF V+
GND
VREFVREG
250Ω
250Ω
250Ω
Tradeoffs cont.
14
4mA
10mA
20mA
1.1V
2.75V
5.5V
+
_
Receiver
+ _
Power
supply
3- wire
Transmitter
(XTR111)
VIN
GND
IOUT
...
DAC
VOUT_1
VOUT_2
VOUT_N
...
VREF V+
GND
REF
V+
+
_
Receiver
3- wire
Transmitter
(XTR111)
VIN
GND
IOUT
V+
+
_
Receiver
3- wire
Transmitter
(XTR111)
VIN
GND
IOUT
V+
VREG
...
Tradeoffs cont.
15
16
Thanks for your time!
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To find more Current Transmitter technical resources and search products, visit: https://www.ti.com/amplifier-circuit/special-function/4-20ma-signal-conditioners.html
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