Comparison of two liquid level transmitters
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There are two liquid level transmission modes marked on the PID diagram.: LSH-LA liquid level chain high---liquid level alarm (high alarm) LT-LA liquid level transmission---liquid level alarm (both high and low) What are the differences between these two transmission modes?
One goes into the chain, if there is ESD, goes into the ESD system, and the other goes into the process control system.
Either the field meters are different, one is a liquid level switch, the other is a liquid level transmitter, or the transmission signals are different, one transmits a 0 or 1 signal, and the other transmits a 4-20mA
LSH is the liquid level switch, DI signal, high liquid level alarm； LT transmits analog signals and AI signals. Different alarm points can be set according to needs, such as high, middle and low alarms. The two signals can enter the DCS or ESD system according to actual needs.
LSH-LA means valve position switch. Both should be sent to DCS for display, but there may not be a link.
The first one should be the liquid level switch and the second one should be the liquid level transmitter.
Both can enter DCS, and the first one can also enter ESD. Both are transmitters, but the first one means that it can trigger a high chain, and the second one can trigger a high alarm at most.
Supplement: Generally, if the first one is simply displayed, it is the status signal 0 or 1.
If it is interlocking, I think it is best to enter SIS or ESD to prevent accidents caused by the pressure of the container. It is possible to take measures such as backup pumps. If an alarm occurs, the interlocking signal can be entered into SIS and DCS. In our case, the interlocking signal usually enters SIS, and then 485 is communicated to DCS or hard wired.
One is a switching signal and the other is an analog signal.
There are two liquid level transmission modes marked on the PID diagram.: LSH-LA liquid level chain high---liquid level alarm (high alarm) should be the DI point LT-LA liquid level transmission---liquid level alarm (both high and low) should be the AI point