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Circuit provides 4  to 20 mA loop for microControllers - 05/27/04 EDN-Design Ideas: The 4- to 20-mA current loop is ubiquitous in the world of controls in manufacturing plants. Discrete logic, microprocessors, and microcontrollers easily cover the digital portions of control schemes. Interfacing a 4- to 20-mA output to a rudimentary microcontroller can be problematic.....(design idea)
Circuit Translates TTY Current Loop to RS232C - 08/03/98 EDN-Design Ideas:   -Provides signal translation between a passive current-loop (TTY) interface and a duplex RS-232C ports.....(design idea)
Current Loop Converter - Two Channel Isolated Industrial Version, schematic in PDF format
Current Loop Interface - (circuit)
Loop powers Current transmitter - 10/28/99 EDN-Design Ideas:.....(design idea)
Low Value Capacitance Meter - This circuit was originally designed to measure the volume of fluid inside a medical syringe.   As designed, it produces a zero to 5 volt output, corresponding to a capacitance change of about 10 picofarads.  With a digital voltmeter, at its output, it can resolve a capacitance change of 0.002 picofarads or 2 femtofarads. ….(designed by David A. Johnson)
Pump Motor Monitor - This circuit can turn on a light or sound a beeper, whenever an AC line powered pump motor turns on.  It is designed to detect the motor current using a small inductor placed on the outside of the motor’s power cable.  No direct wire contact is needed. ….(designed by David A. Johnson)
Selectable Range Current Loop  - Maxim Application Notes / 1085 / Aug-08  (app note)
Temperature Sensor with 4 to 20ma Current Loop - I designed a circuit similar to this one years ago to accurately measure the air temperature inside a building 1000s of feet from a control room.  The circuit uses a very robust current loop method.  It uses a highly accurate semiconductor temperature sensor and an equally accurate voltage reference. The circuit includes a diode bridge, so it is polarity independent.  By using the component values indicated, the circuit should not require calibration.  It has a range from –40F to +120F and an accuracy of +/- one degree F. ….(designed by David A. Johnson)
3V/ 5V DACs Support Intelligent Current Loop - Maxim Application Notes / 722 / Jul-03  (app note)
4 to 20 MCurrent Loop Needs No External Power Source - 09/13/01 EDN-Design Ideas: / PDF contains multiple circuits scroll to find this circuit.....(design idea)
4  to 20 Mloop Needs No External Power Source - 09/13/01 EDN-Design Ideas: simple circuit in Figure 1 uses a low-current-drain MAX407).....(design idea)
Add fault protection to a 4 to 20 mA loop supply - 01/22/04 EDN-Design Ideas: A 4to 20-mA current loop consists of a power source and a current-measuring device at  control end and a field transmitter that senses process-variable information, such as temperature or pressure, and converts it to a current (Figure 1). Most such industrial current loops are powered by 24V dc, but that voltage can range from 12 to 36V.....(design idea)
Circuit provides 4  to 20 mA loop for microControllers - 05/27/04 EDN-Design Ideas: The 4- to 20-mA current loop is ubiquitous in the world of controls in manufacturing plants. Discrete logic, microprocessors, and microcontrollers easily cover the digital portions of control schemes. Interfacing a 4- to 20-mA output to a rudimentary microcontroller can be problematic.....(design idea)
Circuit Translates TTY Current Loop to RS232C - 08/03/98 EDN-Design Ideas:   -Provides signal translation between a passive current-loop (TTY)interface and a duplex RS-232C ports.....(design idea)
Current Loop Converter - Two Channel Isolated Industrial Version, schematic in PDF format)
Current Loop Interface - (circuit)
Loop powers Current transmitter - 10/28/99 EDN-Design Ideas:.....(design idea)
Low Value Capacitance Meter - This circuit was originally designed to measure the volume of fluid inside a medical syringe.   As designed, it produces a zero to 5 volt output, corresponding to a capacitance change of about 10 picofarads.  With a digital voltmeter, at its output, it can resolve a capacitance change of 0.002 picofarads or 2 femtofarads. ….(designed by David A. Johnson)
Pump Motor Monitor - This circuit can turn on a light or sound a beeper, whenever an AC line powered pump motor turns on.  It is designed to detect the motor current using a small inductor placed on the outside of the motor’s power cable.  No direct wire contact is needed. ….(designed by David A. Johnson)
Selectable Range Current Loop  - Maxim Application Notes / 1085 / Aug-08  (app note)
Temperature Sensor with 4 to 20ma Current Loop - I designed a circuit similar to this one years ago to accurately measure the air temperature inside a building 1000s of feet from a control room.  The circuit uses a very robust current loop method.  It uses a highly accurate semiconductor temperature sensor and an equally accurate voltage reference. The circuit includes a diode bridge, so it is polarity independent.  By using the component values indicated, the circuit should not require calibration.  It has a range from –40F to +120F and an accuracy of +/- one degree F. ….(designed by David A. Johnson)
3V/ 5V DACs Support Intelligent Current Loop - Maxim Application Notes / 722 / Jul-03  (app note)
4 to 20 MCurrent Loop Needs No External Power Source - 09/13/01 EDN-Design Ideas: / PDF contains multiple circuits scroll to find this circuit.....(design idea)
4  to 20 Mloop Needs No External Power Source - 09/13/01 EDN-Design Ideas: simple circuit in Figure 1 uses a low-current-drain MAX407).....(design idea)
Add fault protection to a 4 to 20 mA loop supply - 01/22/04 EDN-Design Ideas: A 4to 20-mA current loop consists of a power source and a current-measuring device at  control end and a field transmitter that senses process-variable information, such as temperature or pressure, and converts it to a current (Figure 1). Most such industrial current loops are powered by 24V dc, but that voltage can range from 12 to 36V.....(design idea)
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