4-20 mA loop power simulator help

I need a little help guys. I have built simulators before, oldskool, with resistors and pots. The one i am working on is for a 24vdc loop power circuit, I have built the oldskool one, and it worked. Hook it up to another circuit that is supposed to be identical and it overloads. I am working with Red Lion PAXP, for display and my loop power, I can get it to work on a M2383A, but when i hook up to a M2383B, overload. I guess i need new fangled technology.....

I have a schematic for a transmitter, would it work for a simulator, the transducer has two wires directly from the Red Lion PAXP? Red wire sends 24VDC, black wire receives 4-20mA signal.

http://freecircuitdiagram.com/2010/09/27/op90-4-ma-to-20-ma-current-loop-transmitter/

1) You might consider providing functional descriptions of the devices, along with a model number. I know a Red Lion PAXP is a panel meter, but I have no idea what an M2383A or B is.

2) Avoid the word 'it':

>can get it to work on a M2383A.

Get what to work on a M2383A?

So, I still don't understand what problem you ran into or why it didn't work.

3) For what it's worth, most panel meters take a 4-20mA signal; some model will provide loop power, some models not, some models only if the optional loop power supply is installed. I'm not sure what the PAXP does for loop power.

That freecircuit diagram provies a 20mA loop powered output for a 0-100mV input. Did you realize that it requires a 5V reference (upper left corner).

Red Lion PAXP pin 6 24vdc excitation (loop power), pin 4 20mA input

"it" was referring to the simulator i built, i will try to draw a schematic of the simulator. Not sure if i built it the correct way...but works.

The numbers M2383A and B are on the back of the PAXP meter. If i connect the simulator I built to the PAXP with the A, this simulator seems to work fine, if connected to a PAXP with a B the meter goes into the OLOL state (overload). the only difference I can see on these meters A or B.

i will post my schematic in the morning, unless I need to whip one up.

file:///C:/Documents%20and%20Settings/seth/Desktop/sim.bmp

The PAXP manual does not mention M2838. So who knows what it is? Can you take a photo?

Here's the wiring for a current input:

simulator schematic

The PAXP is connected to a transducer in normal operation. I am trying to build a simulator that replaces the transducer to test connections, wires and so on, in that circuit.

The same simulator has a separate circuit for freq. they use the same pot. I put a NPN transistor between Pin 6 (threshold) and Pin 7 (discharge) on the 555 timer to eliminate interference between the two circuits.

I have discovered different firmware versions for the PAXP. The meter that works with the above schematic is ver. 2.4, 2.5 does not work with this simulator nor does 2.6. Anyone have any ideas as to why, or a idea of what to build?

This is what i have figured out so far, the PAXI receives a freq. signal. The PAXP receives a 4-20mA signal. The transistor is there to stop interference from the 555 circuit when 4-20 is connected. But i still run into the problem of the different versions of firmware and why it works with V2.4 but not 2.5 or 2.6

Red Lion is a couple hours east of you, same time zone.

Why don't you call them and ask them. They're the ones who keep track of firmware changes.

No changes in the firmware that would cause this problem. Tech from Red Lion was very helpful, the problem was that I had, was a couple bad meters. They should have been thrown away but some how got put back on the shelf. If you check resistance across pin 4 (20mA input) and pin 5 (comm.) you should have 20 ohms. On two of these meters I didn't, V2.5 and V2.6, I have since checked my circuit with KNOWN good meters and all works fine. Thanks for your help danw.