I am questioning how to wire an analog sensor to this SIEMENS Analog Input module:

https://support.industry.siemens.co...0sp_ai_8xi_2_4_wire_ba_manual_en-US_en-US.pdf

My sensor has the following terminals: "+" and "GND".

As you can see in the manual there are 2 possible terminals for the first channel: "1" and "9".

Which one should be connected to the "+" on my sensor. I think that should be the "9" but the plus sign on the terminal "1" name makes me doubt.

On the other hand, makes any difference if the sensor is loop powered or not loop powered.

Thanks!

 

Hi

Details on the sensor like the model number would be very helpful.

If the sensor is a two wire type, then i would assume the "+" on your sensor goes to terminal #1 on your module, and the "GND" on your sensor goes to terminal #9 on your module.

Regards
Haidar

 

You don't say whether your field device is 2 wire loop powered, or 4 wire that has separate power terminal connections.

Since you refer to 1 and 9, I'll assume it is a 2 wire loop powered device, because those are the terminals used on the 2 wire diagram on page 11.

On that same diagram on page 11 (2 wire input wiring), it appears that there is a connection between L+ (24V) > 7 (filter) > 3A fuse > 4 (current limiter) to the Uv terminals, of which terminal 9 is a Uv terminal.

I would speculate that 9 is L+, (presumable 24Vdc). If so, then terminal 9 would connect to the (+) terminal on the field transmitter and that the GND (-) terminal would connect to terminal 1, Io+.

Please, put a voltmeter on terminal 9 and tell us whether it has L+ voltage on it.

There might be some configuration or jumper switch needed to convert from voltage inputs to current inputs, 2 wire to 4 wire. I don't know, I didn't read the whole manual.

 

I am glad to see that I am not the only one having doubts with this configuration

I will try to check with a voltimeter if I have 24V on pin 9, but according to the diagram on the manual I am almost sure it will be.

The point is that I have loop powered sensors (temperature and flow) and not loop powered (valve positioner feedback). Does it make any difference in the way they should be wired to the AI module.

Thanks!

 

Hello,

I'm a bit confused because I think that's an easy wiring.

Sensor with 2 wire:
+ supply on 9(10,11,12,13,14,15,16)
out signal on 1(2,3,4,5,6,7,8)

Sensor with 3 wires
+ supply on 9(10,11,12,13,14,15,16)
out signal on 1(2,3,4,5,6,7,8)
- supply on M (or other common of power supply 24V in your plant)

Sensor with 4 wires
+ supply on 9(10,11,12,13,14,15,16)
out(+) signal on 1(2,3,4,5,6,7,8)
out(-) signal on M (or other common of power supply 24V in your plant)
- supply on M (or other common of power supply 24V in your plant)

Hope this helps

regards and happy new 2016
Gabriele Corrieri

 

Thanks for your reply.

What about about a 2-wire not-loop powered signal?

I am using this valve actuator which has an "Active Position Feedback" signal. I understand that the "Active" tag means that the actuator feeds the signal (the actuator is feeded by AC and it should have an AC/DC converter to power the signal).

You can check the wiring instructions on page 11:
http://www.ps-automation.com/files/download_files/OI_AMS1x_PSL_Mod4_ENG_COM_0.pdf

 

Hello

2-wire can be loop powered or not powered: your valve actuator is 2 wire not loop powered, it isn't important by which source powered (ac or dc or everything else) but you consider the output loop that you fill as 4 wire

out(+) signal on 1(2,3,4,5,6,7,8)
out(-) signal on M (or other common of power supply 24V in your plant)

At least consider the galvanic separation from supply and output of your actuator: best is when the output loop is floating, in every condition you must check that out (-) and out (+) NEVER and NEVER are common witb the supply (at least the condition could be that out (-) and neutral (you have written about AC powered actuator) of actuator are joined together: in this condition neutral, and obviously out (-), must be grounded with M of PLC supply.

In our factory we started some years ago (4 or 5) to use current loop sensors and actuators (by explicit request of some customers) and before mount them on machine I'm get an entire day to put them on my workbench one sensor, one actuator, power supply, PLC CPU and subsequent I/O modules for wiring, testing, programming: is very bad modify the wiring on the machine when 100+ sensors are mounted and wired before ... All of this for tell you that current loop isn't hard to understand, isn't not a natural thing when for years you're see only voltage sensors, but if you put the needed time and the required hardware on bench isn't hard to deploy.

Regards
Gabriele Corrieri

 

Gabriele Corrieri's wiring categories are correct; so are the descriptions of the wiring for the active position feedback signal from the electric actuator.

The AC power to the actuator powers the DC power supply inside the actuator that powers any of the actuator's internal logic and its position feedback signal.

If you put a milliampmeter on the output of the position feedback signal, you'll get a mA reading if the actuator is AC powered. The position feedback signal does not need DC power from another source to operate, like your 2 wire loop powered sensors do.