Wiring of transmitter to analog input

Hi guys, I am using Schneider TM2AMM6HT as my analog input module.

I need to wire a transmitter (4-20mA) into the analog input module as in the attached diagram.

The specs of my transmitter are as such:
Supply Voltage: 10 to 30 VDC
Output Signal: 4-20 mA
Current Limitation: 28 mA

Hence my question is:
1) This wiring diagram is given by supplier. Is the wiring diagram correct?
2) For the power supply, it means an external power supply of 24 VDC right?

Thanks.

The diagram looks good, but your supplier ought to know. The power supply can be an external one or you could use the 24 VDC on the PLC rack if you are within its load limits.

Thanks Tom!

However I have another water flow meter, also a passive wiring, but the wiring diagram (as attached) is kind of different from the transmitter wiring diagram above.
The flow meter wiring diagram is given by the supplier themselves too.

Anyone care to explain about the difference? And can the water flow meter wiring diagram work too?

Thanks!

it's not that different. think of it like receiving equipment as input module and display as transmitter and switch their position and you'll notice it's the same thing...

Thanks balash!

however I am using Schneider TM2AMM6HT analog module.

What happened was that when I wired the 24 VDC directly into the receiving equipment (analog module), the PLC module failed/blowed because the permissible overload voltage for the TM2AMM6HT module is 13V.

Hence I am figuring how am I going to wire my flow meter into the PLC. Can I wire it the same way as my transmitter (diagram in the first post)?

Thanks!

Yes, you can wire the flow meter the same way.

A 4-20 mA loop works with either wiring, but people tend to use one or the other on a site.

I do it the first way, 24vdc (+) to the transmitter (+), but it is just personal preference.

Thanks danw!

But what I am interested is why I wire it the second way, the plc blew. But if I wire it the first way, would it be safe that my analog plc module TM2AMM6HT will not fail/blow again?

Thanks.

I'm not familiar with that module, but it's possible the I/O card has a common connection to the - and when you connected your power supply the card short circuited to that connection.

The 13 VDC limit sounds a little goofy. Most cards are more like 30 VDC. Are you sure you have that right?

As a design tool I always draw arrows indicating current direction on my drawings. It is a simple thing, but often helps in diagnosing problems.

that 13vdc is the max voltage if using voltage input as opposed to current, I would go with a common return issue pulling high current through the card.

Thanks Tom and labeledas!

I am pretty sure it is 13V for permissible continuous load.
Also I am not sure what labeledas you meant by go with common return issue with high current through the card.

The issue here is just whether I should connect my plc analog module to the 24 vdc supply. I am just worried I spoil a new analog module again.

Thanks!

>when I wired the 24 VDC directly into the receiving equipment (analog module), the PLC module failed/blowed because the permissible overload voltage for the TM2AMM6HT module is 13V.

Does the AI have an internal dropping resistor, as shown in the first diagram? Is the diagram the PLC documentation or the instrument documentation?

Some analog inputs do not have an internal dropping resistor, they require an external dropping resistor for current signals. A precision 250 ohm resistor is typically used to create 1.0 to 5.0Vdc from the 4-20mA signal.

The AI only 'sees' the relatively low voltage developed as an IR drop across the resistor. The remaining voltage is dropped by the transmitter to regulate the current in the loop.

24Vdc will burn out many AI's if applied directly on the input. Some times a fuse is used to protect the AI should a tech short the tranmitter terminals, which would apply the power supply voltage across the AI terminals.

Loop powered wiring:


I haven't a clue what the difference between 250MEG ohm current input impedance and a more realistic 300 ohm input impedance ohmic value is.



It does infer that there is an internal resistor, though.

I always go tx first for loop powered devices also make sure you are not wiring up to the Voltage inputs

HMM? I can't find where it says the module provides the loop power but it sure looks like it. Hopefully the Modicon gurus will check in here. See drawing below.

Manual link...

https://www.google.com/url?sa=t&rct...pIHoBQ&usg=AFQjCNEi7LfuiEB1MJvEA8JFNkN9aehSow

You wire the DC+ to the transmitter and the 4-20mA signal to I0. You also have to wire one COM on the card to DC-. For current you must also jumper I0 to V0 because that connects an internal 250 ohm resistor. I know this because if you configure the module for voltage but hook up current, the input is half as 0-5V would be.