Transmitter is Chinese name, English is: transmitter
As the name suggests, transmitters contain "change" and "send" meaning.
The term "change" refers to the conversion of various physical quantities from the sensor to an electrical signal. For example: The use of thermocouples, the temperature into electric potential, the use of current transformers, the large current into small current. Because electrical signals are easiest to handle, modern transmitters are transformed into electrical signals by various physical signals. So, the transmitter that we are talking about is usually turned into "electricity".
The so-called "send" refers to the various electrical signals that have been turned into, in order to facilitate the reception and transmission of other instruments or control devices, once again through the electronic circuit, the sensor to the electrical signals, unified (such as 4-20ma). The method is implemented through multiple operational amplifiers. This "change" + "send", on the composition of the most commonly used in modern transmitters.
For example: Sst3-ad is a kind of current transformer output current, into a standard 4-20ma of the current transmitter; again, for example: Sst4-ld, the weight sensor can be converted into a standard 4-20ma weight transmitter.