Created Date: February 28,2007

Created by: FACTSTech

AZRoger,

You will need 2 FC-11 signal conditioners for isolation. One transmitter driving the 2 FC-11 inputs, then wire each output respectively to the analog module channels.

As for the Track & Hold can be changed on the fly. Are you looking for a peak or valley at 1 minute intervals or looking for the max & min value? If the latter, the module takes care of this for you, i.e. input current is 4.83mA, then jumps to 5.62 mA, this current value would then be displayed in Vmemory, when the next higher value jumps data jumps to the new value.

Broken transmitter bits are only 8 X's

Created Date: March 01,2007

Created by: AZRoger

FACTSTech,

Wow. I had no idea these current loop modules were so tough to use. I was already having trouble getting (a) the recommended 32mA fuse from AD and (b) fuse holders in quantities less than 50. Now I can't split one of the inputs without two $89 signal conditioners. http://forum1.automationdirect.com/board/frown.gif

Let's try another approach. Substitute the F2-8AD3DA-2 analog voltage module. I'll use an external resistor to convert my 4-20mA transmitter's output to volts. The -2 module has 1 Meg Ohm input impedance. There should be no problem hooking two of these inputs to the same voltage source. Right?

This leaves one question. Each input in the module can track either min or max but not both at the same time. That's why I am trying to use two inputs looking at the same transmitter. For each minute of sampling, I want to capture both min and max for the same minute from the same transmitter. This means two inputs, right?

After each minute's data is saved, I need to reset the input for the next interval. On page 16-15, the Track and Hold bits are described. It says they can be changed "on the fly ". How really "on the fly " is that?

Can I have a rung that sets the control bits to 11 (for reset) and then immediately sets then back to 10 (Max) or 01 (Min)? Will this cause the reset to occur?

Or must I wait for one scan between requesting reset and going back to Max or Min tracking?

Roger

Created Date: March 05,2007

Created by: FACTSTech

Roger,

I was going to suggest using the voltage module and one loop resistor, but it seemed you wanted to use the current module.

Yes you must use 2 separate inputs to do min/max as you are describing in your application.

As for "on the fly " this is what it means

1st scan reset (11) 2nd scan set channel #1 (01)and channel #2 (10). They will then capture the min/max data, then for your next DUT, reset scan, set channels scan.

Created Date: March 06,2007

Created by: AZRoger

FACTSTech,

I have ordered the -2 (voltage) part and it should be here shortly. My transmitters are 4-20mA so I mentioned a current part in my topic header. I got too specific in my original question about how to use the module. We could have come to your "use the voltage part with a loop resistor " suggestion a couple posts earlier. Thanks for the clarifications.

Roger

Created Date: February 28,2007

Created by: AZRoger

Hi,

While deciding on an analog module, I discovered that this one has "Track and Hold " functions. I'm trying to capture minimum and maximum values on a 1 minute cycle. I had planned lots of sampling in the ladder logic with a "save and reset " function each minute. This module would make that lots easier.

I'd like to hook one transmitter to two inputs. This would allow one to track the max and one the min. I read the following post from long ago about hooking more than one input to the same transmitter.

http://forum1.automationdirect.com/board/Forum1/HTML/000179.html

That thread says you need to hook the inputs in series to get them both to see the same 4-20mA signal. That won't work with this module. All the inputs share a common ground inside the module.

However, if I hook them in parallel, both inputs should see half the current. This assumes that both inputs have equally exactly 100 ohm shunt resistors. If I can live with 2-10 mA (1/2 scale) wouldn't this work? The 8-in/4-out module allows 14 or 16 bit accuracy as well as the more usual 12 bit. Couldn't I use the engineering unit scaling routine to get the right values? With 14 bit input, I could even get twice the accuracy as the regular 12 bit even though I'm seeing only 1/2 the current.

Assuming the wiring and scaling stuff is OK, I have a programming question. The track and hold control bits are in V-memory. To perform my once-a-minute processing, I think I need to reset the Track and Hold bits on one scan and then reactivate them on the next. No immediate I/O function exists for V-memory. Is this correct?

Finally, using the pointer method with 8 inputs, is there any practical use for the 24 input Xs that aren't the "broken transmitter " indicators?

I can save a lot of ladder logic if this works as I hope. My fingers are crossed.

Roger