In level gauges, what are the respective functions of 4-20mA and 485? What’s the difference from HART?
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In level gauges, what are the respective functions of 4-20mA and 485? What’s the difference from HART?
These two things have nothing to do with each other; 4-20MA transmits a standard current signal, while 485 is a communication protocol.
It seems the poster has also just started working with instruments
Well, do you mean that too? Are you the same? ;P
What is the method of communication? Seeking advice from an expert: handshake
Find some information to look at; there’s too much text to explain everything at once
4-20mA: Analog signal; 485: Digital signal, typically using the MODBUS protocol; HART: Digital signal, a type of communication protocol. It is generally used in combination with 4-20mA.
I’ve learned it: handshake. One more question: what are the different functions of each of them?
4-20mA can transmit the meter’s measurement value as an analog signal to a secondary instrument or control system; generally, only the measurement value is transmitted； RS485 generally uses the MODBUS protocol to transmit the meter’s measurement values, status, alarms, etc. in digital form to the MODBUS master station ； The HART protocol is typically used in conjunction with 4-20mA signals; it is possible to configure the instrument using a handheld programmer, and control systems that support HART can detect whether there are any faults with the instrument. Simply put, it means that the measurement values are transmitted via 4-20mA ； MODBUS can transmit the alarm values and fault status of level gauges, etc ； The HART protocol allows the handheld communicator to set parameters such as the measurement range of the instrument. Control systems generally receive 4-20mA signals, corresponding to the set physical range.