4-20ma current transmitter

[scarg]

Greetings,

Does anyone know of a relatively inexpensive handheld unit that will out put a (user) variable 4-20 ma current to test signal acceptance on a Hitachi L100 VFD? By inexpensive I mean <$100 or so. Not something that I will use often but it would be valuable for testing equipment for proper factory setup and troubleshooting in the field.

Best Regards,

Steve

 

[jraef]

By a battery that is easy to connect to, a dropping resistor and a 10-turn potentiometer. Depending on the battery voltage you end up finding, size the resistor and pot with the burden resistance of your VFD analog input so that as you change the pot resistance, you induce a flow of current between 0 and 25ma. Use Ohms law combined with the availability of components at your disposal to figure out what combination to select, then just test it with a multimeter to see where the range is. I built mine for about $6 total with parts from an electroics &quot;junk&quot; dealer, and $3 was for the 6V lantern battery! (I use that because it has the spring terminals that are easy to clamp on to with aligator clips)

Quando Omni Flunkus Moritati

 

[jbartos]

Suggestion: Visit

http://www.thomasregister.com

and type Transmitters: Current under Product or Service, which will return 9 companies to approach to

 

[OperaHouse]

Use a 7805 regulator in current mode. This has three terminals IN, OUT and COMMON. Use a 0.1 cap from IN and OUT to COMMON. Use two 9V alkaline batteries in series. Connect + to IN. Place a resistor from IN to COMMON. Use ohms law to figure out the current with 5V. Selector switch or pot can give you diferent currents. Just remember, pot has to be able th take 20 ma. Common and bat minus are your current leads. Doesn't even need a switch. DVM verifies current.