impedance question

Its been a long long time since I done stuff like this. So my question is How does impendance on a analog output card (ie. Siemens Sm332) affect what can be directly connected to it. As in do you need a external resistor or anything else...

Given the specs:
Load impedance
- 1K for voltage out
- 1uF fo capactive load out
- 500 ohm current out
- 10mH with current output, inductive loading....

I think this is a really simple question for most of you. I like to see examples maybe with calculations.

Thanks.

These are maximum limits. The most the card can supply. For example, voltage out - at 1K, a 10.00 output voltage would be 10.00. 10V/1000 = 10mA output current. In other words, the most current the card can supply in voltage mode is 10mA. It probably can supply more, but they don't guarantee specs at greater than 10mA.
If maximum voltage is 5 volts, then maximum current is 20mA. This is more likely, and fits with the next spec of 500 ohm in current mode.

Thanks.

PM pulled to Forum

(Maybe I should have started a new thread, but close enough)

cotang said:

Thanks for the help with the impedance question. I was wondering if you can help me with the next one.
I have an analog module Siemens 331-7KF02-0AB0. I'm trying to find the load requirement for a 4-20mA setting. The impedance relative to the input is 150, 300, and 600 (from the tech spec) I'm not sure which one I should be using or if I'm even looking at the right part.
Any help is appreciated.
Thanks.

Click to expand...

4-20 mA translates to 1-5 volts or 2-10V inside the Analog Input card. Connect a 250 ohm resistor across the input terminals of a 1-5 volt input, and it becomes a 4-20 mA input. Typical is 250 ohms. AD uses 500 ohms.
The input resistance you describe is for Thermistors, Mode A.
You should use Mode D for 4-20 mA. See page 281 of S7-300 Automation System Module Data Manual, 02/2007, A5E00105505-05.

Download here.
When searhing for info, use the full part number. 6ES7331-7KF02-0AB0