Hi, I plan to connect my a/d chip to a 4-20 ma sensor (a Honewell sensepoint). As my a/d is 0-5v input, I assume I would also connect the 0v from the power supply to my 0v on my board, as it has its own power supply. Would this be correct?
Great video! I am not new to electronics but it is my first time to work with 4-20mA current loop transducers and don't know much about the industry instrumentation standards.
Your video helps a lot! Now my question is, may I assume that all transducers with 4-20mA current output have constant current source built-in?
@sfacp If the sensor is 4-20 mA DC, then you may safely assume it's got either a current regulator in it (2-wire) or a true current source in it (4-wire). Read the chapter in my book on analog instrumentation signals:
openbookproject (dot) net (slash) books (slash) socratic (slash) sinst (slash) book (slash) liii.pdf
@BTCInstrumentation Thanks a lot for your answer. And thank you for your book too. It 's a wonderful book for me to learn industry instrumentation. Do you offer a online course for this?
@Mart34 Most loop-powered transmitters have minimum and maximum terminal voltages ranging around 12 to 40 VDC. Specifications vary, so be sure to check the manufacturer documentation (datasheets, user's manuals) to get a definitive answer for your transmitter.
Maximum loop resistance is a function of minimum terminal voltage. Loop resistance drops voltage, taking away from the power supply voltage, leaving the transmitter whatever remains. R_max = (V_supply - V_min) / 20 mA
Hello, I am working on developing a simple training curriculum regarding 4-20ma current loops. I work in the industrial burner/boiler industry. Our industry has just about completely converted to 100% electronic controls and the use of 4-20ma current loops is very wide-spread. I am trying to find a nice simple, easy to view graphic of a 2-wire current loop circuit to demonstrate with. Would you happen to know a good example of one on the net or perhaps have one yourself? Any help would be great
@nugent5438 Sure thing: check out my free textbook online, with a whole chapter on analog instrumentation signals. Pardon the weird URL, as YouTUbe does not allow me to post it verbatim:
openbookproject (dot) net (slash) books (slash) socratic (slash) sinst (slash) book (slash) liii.pdf
@mcr1981 Typically three-wire transmitters take in DC power on two wires (typically red and black) and output an analog voltage signal between the third wire and DC ground (white and black). Can't be sure though until you consult the manufacturer's documentation. Every transmitter I've ever worked with has some sort of documentation in the manual showing how to hook it up.
Hi, thanks for the reply. I got a pressure sensor on a "garage sale" (company went bankrupt) from a friend. I'm starting with electronics and went to the machine shop of another friend to test the pressure. I connected the sensor to a power supply (15-50v) and I tried to measure the output (4-20mA). Three wires: red, black and white. Positive power supply terminal to red, negative terminal to black, and the white I used as the current terminal (output). I had no luck.
@mcr1981 The output signal may very well be voltage, not current. Anyway, the only sure answer is to research the documenation for this instrument and see what the manufacturer tells you. Most instrument manufacturers provide downloadable user's manuals for their products online. Go forth and Google!
@mcr1981 Google-search for "Sensotec 811 FMA" and go for the third hit. It's a catalog showing all the Sensotec products. They give wiring details on pages AP-8 through AP-11. The schematics show up on my screen pretty grainy, but the text spells out which wires do which functions. Hope this helps!
Wiring detail #22 on page AP-10 says the white wire is nothing but a case ground, so it's really a two-wire transmitter: Red (+) and Black (-). Therefore it should work just like the transmitter shown in the video. Note that the "FMA" is an *absolute* pressure transmitter, so it will probably give an output greater than 4 mA at atmospheric pressure (i.e. it should output 4 mA at a perfect vacuum).
Thanks for your help. I'll check the sensor tomorrow at my friend's shop. If all goes well, I'll try to make a video of it.
I said I'm new to electronics, that's wrong, I'm new to this sensor type electronics. Will look into the constant current thing in the sensor (change load but same current?). You got me there.
@mcr1981 It's sometimes helpful to imagine the 4-20 mA transmitter as a continuously-adjusting variable resistance, increasing or decreasing as needed to hold the circuit current wherever it should be. Thus, if some other resistance (load) in the circuit changes value, the transmitter senses the resulting change in current and immediately compensates by changing its resistance in complementary fashion to bring the current back to where it belongs.
we tested it and had 4.65mA at 0 PSI (indicator). We'll work on an ecuation for a microcontroller. I'll post information on it. 340 psiA is a lot!!!!!
Sorry, this is the last part of the explanation (500 characters is not enough).
The sensor is a Sensotec 811 FMA pressure sensor. The data on the sensor states that it is a 4-20mA sensor output but it says it's two wire insted of three..... that is what I don't understand. I looked for a solution "how to connect three wire sensor" on the net but no luck. Until I landed here (great video by the way).
Thanks for your help. If you can help me I'm be very grateful.
Hi, I plan to connect my a/d chip to a 4-20 ma sensor (a Honewell sensepoint). As my a/d is 0-5v input, I assume I would also connect the 0v from the power supply to my 0v on my board, as it has its own power supply. Would this be correct?
Thanks
Scott
neil230163 4 months ago
Thanks for your upload and book.
jacknay112 4 months ago
Molt ben explicat
jaumetebe 4 months ago
Great stuff, your videos are the best on here.. thanks alot.
rpaul247 11 months ago
Great video! I am not new to electronics but it is my first time to work with 4-20mA current loop transducers and don't know much about the industry instrumentation standards.
Your video helps a lot! Now my question is, may I assume that all transducers with 4-20mA current output have constant current source built-in?
sfacp 1 year ago
@sfacp If the sensor is 4-20 mA DC, then you may safely assume it's got either a current regulator in it (2-wire) or a true current source in it (4-wire). Read the chapter in my book on analog instrumentation signals:
openbookproject (dot) net (slash) books (slash) socratic (slash) sinst (slash) book (slash) liii.pdf
BTCInstrumentation 1 year ago
@BTCInstrumentation Thanks a lot for your answer. And thank you for your book too. It 's a wonderful book for me to learn industry instrumentation. Do you offer a online course for this?
sfacp 1 year ago
Comment removed
sfacp 1 year ago
Comment removed
sfacp 1 year ago
Comment removed
sfacp 1 year ago
Excellant video. Whats the maximum loop resistance and less importantly, whats the max voltage you can apply ? cheers, mart
Mart34 1 year ago
@Mart34 Most loop-powered transmitters have minimum and maximum terminal voltages ranging around 12 to 40 VDC. Specifications vary, so be sure to check the manufacturer documentation (datasheets, user's manuals) to get a definitive answer for your transmitter.
Maximum loop resistance is a function of minimum terminal voltage. Loop resistance drops voltage, taking away from the power supply voltage, leaving the transmitter whatever remains. R_max = (V_supply - V_min) / 20 mA
BTCInstrumentation 1 year ago
Hello, I am working on developing a simple training curriculum regarding 4-20ma current loops. I work in the industrial burner/boiler industry. Our industry has just about completely converted to 100% electronic controls and the use of 4-20ma current loops is very wide-spread. I am trying to find a nice simple, easy to view graphic of a 2-wire current loop circuit to demonstrate with. Would you happen to know a good example of one on the net or perhaps have one yourself? Any help would be great
nugent5438 1 year ago
@nugent5438 Sure thing: check out my free textbook online, with a whole chapter on analog instrumentation signals. Pardon the weird URL, as YouTUbe does not allow me to post it verbatim:
openbookproject (dot) net (slash) books (slash) socratic (slash) sinst (slash) book (slash) liii.pdf
BTCInstrumentation 1 year ago
Comment removed
nugent5438 1 year ago
How do you connect a three wire transmitter? Black, Red and White
mcr1981 1 year ago
@mcr1981 Typically three-wire transmitters take in DC power on two wires (typically red and black) and output an analog voltage signal between the third wire and DC ground (white and black). Can't be sure though until you consult the manufacturer's documentation. Every transmitter I've ever worked with has some sort of documentation in the manual showing how to hook it up.
BTCInstrumentation 1 year ago
@BTCInstrumentation
Hi, thanks for the reply. I got a pressure sensor on a "garage sale" (company went bankrupt) from a friend. I'm starting with electronics and went to the machine shop of another friend to test the pressure. I connected the sensor to a power supply (15-50v) and I tried to measure the output (4-20mA). Three wires: red, black and white. Positive power supply terminal to red, negative terminal to black, and the white I used as the current terminal (output). I had no luck.
mcr1981 1 year ago
@mcr1981 The output signal may very well be voltage, not current. Anyway, the only sure answer is to research the documenation for this instrument and see what the manufacturer tells you. Most instrument manufacturers provide downloadable user's manuals for their products online. Go forth and Google!
BTCInstrumentation 1 year ago
@mcr1981 Google-search for "Sensotec 811 FMA" and go for the third hit. It's a catalog showing all the Sensotec products. They give wiring details on pages AP-8 through AP-11. The schematics show up on my screen pretty grainy, but the text spells out which wires do which functions. Hope this helps!
BTCInstrumentation 1 year ago
Wiring detail #22 on page AP-10 says the white wire is nothing but a case ground, so it's really a two-wire transmitter: Red (+) and Black (-). Therefore it should work just like the transmitter shown in the video. Note that the "FMA" is an *absolute* pressure transmitter, so it will probably give an output greater than 4 mA at atmospheric pressure (i.e. it should output 4 mA at a perfect vacuum).
BTCInstrumentation 1 year ago
@BTCInstrumentation
Thanks for your help. I'll check the sensor tomorrow at my friend's shop. If all goes well, I'll try to make a video of it.
I said I'm new to electronics, that's wrong, I'm new to this sensor type electronics. Will look into the constant current thing in the sensor (change load but same current?). You got me there.
mcr1981 1 year ago
@mcr1981 It's sometimes helpful to imagine the 4-20 mA transmitter as a continuously-adjusting variable resistance, increasing or decreasing as needed to hold the circuit current wherever it should be. Thus, if some other resistance (load) in the circuit changes value, the transmitter senses the resulting change in current and immediately compensates by changing its resistance in complementary fashion to bring the current back to where it belongs.
BTCInstrumentation 1 year ago
@BTCInstrumentation
Hi. Thanks for the information.
About the sensor:
we tested it and had 4.65mA at 0 PSI (indicator). We'll work on an ecuation for a microcontroller. I'll post information on it. 340 psiA is a lot!!!!!
mcr1981 1 year ago
@BTCInstrumentation
Sorry, this is the last part of the explanation (500 characters is not enough).
The sensor is a Sensotec 811 FMA pressure sensor. The data on the sensor states that it is a 4-20mA sensor output but it says it's two wire insted of three..... that is what I don't understand. I looked for a solution "how to connect three wire sensor" on the net but no luck. Until I landed here (great video by the way).
Thanks for your help. If you can help me I'm be very grateful.
mcr1981 1 year ago
exelente aporte, aun que esta explicado en ingles algo se logra entender saludos BTC instrumentacion
rebandido777 1 year ago
You did a great job explaining the pressure transducer. I like your video lessons on you tube.
I allways look for more knowledge on your you tube lessons. Thank You.
rayram55 2 years ago