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Modbus is a protocol that covers all of your requirements. The specs are at https://modbus.org/tech.php but you will find quite a bit is you just google it.
Re: Hello Frends...:-).. Eager to know how a "True RMS is calculated inside multimete
I am sure that it will depend on the DVM. I seem to remember the old Flukes (like 8060 type) used an external True RMS chip.
I suggest the following article as a good starting point:
**broken link removed**
Other factors that can affect the choice is whether the part is readily available and if it already exists in my company's database.
On the design side you should pay attention to fact that the track resistance can play into the voltage measurement. If you are not using a CSR with Thevenin...
I must stress that I have NOT followed all your description (my time is limited) so my advice is first to move with caution. I would start out trying to connect from your 0V to earth-ground with a 100R resistor (use as high wattage as you have). Then measure if there is a voltage drop across it...
I am not really sure of your set up, but the isolated 0 of the transformer is floating like everything thing else. If your power supply is isolated, then there should be no problem in fixing the potential by connecting the 0V to Earth-Ground.
From what you have said, I am not sure you have a common reference between the two systems. As I understand it youy only have the 2 wire A & B connecting the systems. If that is the case it is likely that one is floating against the other and sooner or later you are going to violate the +12/-7V...
This is good, except for good engineering design you still have to ensure you are drawing enough current out of the base of the PNP to ensure it in in saturation as well (in all conditions where the design is used). On the assumption that you are pushing 6mA into the base of the NPN, this makes...
The whole point of switching transistors is when they are on they should be driven to saturation. Now if I remember correctly, the second transistor
in the darlington pair never saturates, which is why the on voltage is ~1.2V. But what you are suggesting will result in the pair entering the...
You can actually do this by calculation. To guarantee that a transistor is saturated you need to drive the base of the transistor with a current that is 10x the base current based on the gain of the transistor. (There is some discussion on whether 10x is overkill, but let's leave that for the...
Depending on your power requirements, you could use drive a D/A from your micro generating a variable peak AC waveform. Follow that with a power amplifier which drives (AC coupled) a step up transformer. No (electro) mechanical devices are needed. You could make your own power amp using...
Sourcing 4-20mA can be a little more complicated, especially if you are using loop power. I suggest you read my article in Circuit Cellar Issue 241, of August 2010 entitled "The 4-to-20-mA Current Loop". It covers current sources made up of individual parts as well as dedicated ICs.
**broken...
Some more app notes that have just come to my attention on the subject (adding details of additional transient supression)
https://www.bourns.com/data/global/pdfs/bourns_cpk1114_rs485_circuit_protection_appnote.pdf#search=%220038194856 07ca59485 167485 2485 3485 4485 485 4850 548502 564851...
The response time of the zeners is much slower than the TVS, so if you suspect that there are very fast transients the TVS is the way to go. This is also probably the preferential way to go if you are looking for CE certification.
For slower signals they will both clamp, and the incoming...
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