And finally i know why they use current balance relay on telephone stuff.http://www.pacontrol.com/download/4-20mA-Current-Loop-Primer.pdf a 4-20mA circuit is a current loop. the most common power supply for 4-20mA loops is 24V, but can use anywhere from 12V to 36V. for digital data, 4mA is a "0", 20mA is a "1". current loops are often used for connecting industrial equipment to a controller, but they have been used for teletype lines, and a standard telephone works on a similar principle, except the variations in current carry analog signals. the power supply for current loop communications is usually a "floating" supply, and there is no signal ground.
If you put a 250 ohm resistor across your sensor's output, it will generate a 1 to 5 V signal (see ohms law for reference).Can we use it with 4-20mA circuit or not ?
Yes, I use 24 volt switch mode power supplies all the time with sensors having a 4 to 20 mA output. You can use a SMPS or a Linear regulated DC power source. Here is an example of a SMPS (SOLA 24 VDC) power supply powering four each temperature sensors with each having a 4 to 20 mA output. Then as Gopher mentions each 4 to 20 mA loop is passed through a 250 Ohm 1% precision resistor providing 1 to 5 VDC which is passed to an ADC.Can we use it with 4-20mA circuit or not ?
Ok so you mean to say that these will help me to use less gpio pins will make my sensors much more power efficient ?Very simple, just look at the feature set, that you don't get with a simple resistor.
I would also add that these modules very likely have extensive fault protections.
- 4 Channel 4-20 mA Current Loop Receiver
- 4-Channel Input with 16-Bit Resolution
- 4-20mA Industrial Sensor Monitoring
- INA196 Current Shunt Monitoring
- Ideal for Sensor and Instrument Monitoring
- ADS1115 16-Bit Analog to Digital Converter
- Onboard 16V Voltage Supply (Boosted from 5V)
- Ideal for Industrial Automation 4-20mA input