6/25/2014 11:26 AM | |
Posts: 1 Rating: (0) |
What is the Part Number? |
6/28/2014 9:20 AM | |
Posts: 209 Rating: (2) |
Hi celsius, I have attached our schematic diagram for the connection of our Sitrans P MPS. Unfortunately, we have not installed any protection like surge protectors because we thought it wouldn't be necessary. Our Power supply is also used in different sensors. So maybe if the power supply is faulty it would also destroy the other sensors. Maybe I should put some surge protectors?? What can you suggest?? Thanks for the help AttachmentR17.pdf (256 Downloads) |
6/28/2014 4:17 PM | |
Joined: 3/28/2010 Last visit: 9/21/2024 Posts: 1056 Rating: (213) |
You need to 'divide and conquor' and determine which devices are faulty. Put a milliamp source (calibrator) on the analog input (AI) to see if the AI is still functional and reading the current source properly. There is a possibility that the AI could be giving a bad reading from a good transmitter. At the same time, you should check the loop current from the transmitter with something other than your AI (loop calibrator or a voltage source and a mA meter) and see if the loop current is 4-20mA or whether it's really 40+ mA. A properly functioning, submersible head pressure, 2 wire, loop powered level transmitter will not produce 40+mA. If it does go to 40+mA, it was damaged beyond repair. Submersible pressure transmitters like these are typically electrically isolated, or 'floating'. So a transmitter connection to the PLC should not have provided a low resistance earth ground path for lightning. But lightning does what it wants. Direct hits incinerate (burn up) things, If the transmitter is faulty, I think it more likely that the fault was caused by induced voltage on the lead wires. Most vendors offer optional surge protection built in to the submersible, protecting it at the electronics end, because the lead wire can be an antenna picking up induced voltage. It can't hurt to put a loop surge protector in the circuit 'up top', but it's no guarantee. You might consider surge protecting the control panel power, too. There's a write-up on integrated surge protection at this link http://tinyurl.com/nnn43x6 |
7/1/2014 8:15 PM | |
Joined: 3/28/2010 Last visit: 9/21/2024 Posts: 1056 Rating: (213) |
Principle of surge protectors: Surge protectors have 2 sides, an input and an output. The input side is not protected, output side is protected. Rule of thumb: put the surge protection as physically close to the device being protected as is feasible. Phoenix Contact has an excellent app note, 2554A, on surge protection for 4-20mA transmitters and their control systems. http://tinyurl.com/lqfyg2y Note that page 1 shows the use of two surge protectors, one at the transmitter to protect it and another at the control system end to protect it. The wire run is in between with a surge protector at each end. Page 2 shows an unprotected field transmitter and a protected control system. If reversed, the transmitter could be protected and the control system unprotected. If it were me, I'd protect both. I would also opt for the PT...+F-BE base which isolates the shield and ground, preventing a ground loop. |
This contribution was helpful to1 thankful Users |