8-channel analog output module

Hello everyone.
I am trying to test a analog output, but not getting the expected result.
In the HW conf. the config is current 4-20
in the logic Iam mult the output of a PID (0-100) by 276.48 t0 get 0-27648 and moving that into my output word PQW262.
when the value of PQW262 is CERO I get 4ma,messure acro terminal 3 and 6.
when I increse the value of PQW the ma go down to 1.6ma
Any Ideas about what I am doing wrong
see a couple of pictures attached




thanks

The picture Conf,is for the 2 analog outputs on the 314c-2dp wich are acting the same way.

I'm assuming that you have a 15 bit output such that 32767 produces a 20 mA output and .2 x that (6553.4) produces 4mA. So reverse engineering, I would seek to first produce 0 - 26214 (0 - 80%) of 32767 corrosponding to 0 - 16 mA. If your starting with 0 - 100%, then 26214/100=262.14
Therefore your math needs to produce the following:
(Raw Output x 262.14)+6553.4 which will produce your 0-16 mA and then offset it to 4-20mA.

I always model the math in Excel and then save it with the application program. Later, you can take the Raw values and inset them in Excel and it will tell you exactly what the system should be doing.

The kills three birds with a single stone:
1) Provides documentation
2) The model provides for troubleshooting
3) It is a great way to train the next persion who gets to take care of it.

Best Regards,

Bob A.

it is Simatic 332-5HF00-0AB0 8-point 12 bit Analog output card. manual says 4-20 = 0-27648

FAGARCIA said:

it is Simatic 332-5HF00-0AB0 8-point 12 bit Analog output card. manual says 4-20 = 0-27648

Click to expand...

I believe this card has 4 sided blocks on the side that have to be oriented correctly for voltage or current. Have you done that?

no.

I configure each channel to be 4-20 on the hw configuration only.

FAGARCIA said:

no.

I configure each channel to be 4-20 on the hw configuration only.

Click to expand...

I would check for any type of configuration block or jumpers on the card. I can't recall for certain and don't have the manuals in front of me, but I do know that some of the Analog modules have either a bank of jumpers or a 'block' that has to be oriented correctly for current or voltage. There are also a different set of terminals to wire to whether you are sourcing current or voltage, so check your wiring too.

If your current is dropping it certainly sounds like either a wiring or hardware configuration problem.

Is the measurement with a 'load'?
Is terminal 6 connected to the ground?
Is the 24VDC connected to terminal 1 (+) and 20 (-)?
Are the grounds (terminal 6 for example) connected to terminal 20 (-)?

I've seen some funny measurements with the 4-20mA cards. Until we wired em exaclty how it is shown in the manual.

Edit: The analog output cards from Siemens don't have the 4 side blocks. It seems only the analog input cards have em.

in the logic Iam mult the output of a PID (0-100) by 276.48 t0 get 0-27648 and moving that into my output word PQW262.

Click to expand...

Can you post the code for the above processing.

logic as requested

Looking at the values I realize that I am not really sendind 27648.
that number is the shown on the screen but the display was in floating point, when changed to decimal is a much bigger number.

My problem now is not the output card but the logic to convert the real to decimal.

I enter 0-27648 directly into the PQW an I get the right 4-20ma

Here's some code that will work:


As an alternative you could use FC106 (Unscale) from the Siemens library.