Analog signal generators

[ReggieJohnson]

Thanks for the help on my last question, here's round two.The renewable energy system I'm building for is still in its development stage and we have some really bright and talented Mechanical Engineers, that being said, the focus of bring cost down is leading to some interesting sensor products being used. The field I/O devices are from MetzConnect, (EU I think) and mainly used in the HVAC industry. The analog input units can only handle voltage inputs, RTD's, 1-5 v, millivolt, etc. I need to find a signal generator to test (not calibrate) these inputs as well as 4-20 ma. that will be converted to 1-5v. My panels will be built in Nevada and programmed from Toronto via web so I need to send simulated signals to test the channels and verify comms are up. Any thoughts, good luck with a product, or pushing one of your own, let me know. I have a few weeks before getting started on the next design. Check these guys out, pretty cool stuff at the tip of the spear... Bright Energy Storage Technologies Bright Rail Energy SkyLouver Systems

[Mendon Systems]

It seems like the simplest way to solve your problem would be a second PLC with analog outputs and a simulation program to generate the signals that you need.

[RussB]

Sorry but I don't have time to do all of your research for you.

[ReggieJohnson]

#facepalm (Duh, big red truck).....Dick, thanks for getting me off that path to nowhere. Nobody to talk to around here except wife, kids and dogs. Still it would be nice to find a portable tester for field service. Russ thats not a plea for help......:) 15th Med, 1st Cav

[ReggieJohnson]

Dont know why my name isnt showing up, Reggie Johnson

[Mendon Systems]

I suppose you could use something like a Fluke 787 to do field simulation, but that would be limited to one analog channel at a time. It would probably be almost as easy just to make your simulation PLC into a portable unit. I'm sort of interested in your project. I have been building panels with a company near here for several years that is trying to develop something similar. Edited October 16, 2015 by Mendon Systems

[ReggieJohnson]

I guess its official catagory is daylight harvesting systems, they are using embedded PC to control but rest of system is pretty standard sensors, pumps, etc. Hit me up on skype, 775-434-7939 or email reggie@rwjc.us

[kaiser_will]

You want a programmable controller with various analog outputs so you can generate signals to verify the embedded PC controller logic functions properly? Could you use a 2nd embedded PC controller to generate analog signals? If that is not an option, then you will probably need test points identified and a written test procedure.

[ReggieJohnson]

This embedded PC doesnt have AO capability. I'm not sure I will be a big fan of these $100,00 PCB's inside an industrial panel anyway. I probably was over thinking this need. I could test the system with three of their sensors, a RTD, an anamometer, and a light level sensor. Thanks for trying to help.....

[kaiser_will]

It does sound like you have the need for a PLC panel to generate the signals. Is there a PLC platform you are comfortable with? I personally would specify an Allen-Bradley CompactLogix system. Add a basic PanelPC with the Logix software; configure networking to use the company LAN; install TeamViewer or similar remote connection software; then you can remotely connect, run your testing, verify proper performance. If you are an A-B integrator you get Logix5000 and FTViewME already; you could create a FTViewME application and run it, like having an HMI without having to buy an HMI.

[DanW]

Here's a static, single value test that I used once. If the value is not within some reasonable tolerance, it's a misconfigured input. Multiple voltage inputs can be fed in parallel from a common DC voltage source with only minor impedance errors. A 2 wire RTD can be simulated with a resistor, a 3 wire RTD simulated with a resistor and jumper. I use 120 ohm resistors because I buy them in bulk for terminating serial RS-485 networks. Pick a common value, they're pennies each from a electronic distributor. 4-20mA current signals can be done in multiples. Using 12mA as a midscale value, a conventional 24Vdc power supply can drive 2000 ohms at 12mA. If each analog input uses a 250 ohm input resistance, then the 24Vdc supply will drive current through 8 inputs in series. A low cost 1A DC supply could run dozens of these 8 channel series loops. This concept works for isolated inputs. Single ended inputs will see excessive common mode and either saturate at full scale or even burn out. When I've done this, I used extra analog input terminal blocks and wired them for the function needed, removed the field wired terminal block and stuck the test terminal block on for the test. Edited November 22, 2015 by DanW

[ReggieJohnson]

Awesome,.thanks