Loop Resistance Questions

This is a diagram of how we connect transmitters to analog input modules.

Check if your transmitter is getting power (display should have some indication). If you have a milliamp meter (most digital multi-testers would have this), connect it in series with your transmitter. You should be able to read between 4 and 20 milliamps. Next, check between the + of the analog input card and COM. You should have about 250Ω there. If it's not there, check your module's manual. Maybe you need to change a DIP switch or jumper on the card.

regards,

Vulcan

Thank you for your valid comments ,still some doubts are pending as given below,

in my transmitter ther are 3 terminals by name ,"supply (+,-) and check",I gave supply 24v externally to supply to the supply terminals....and tok signal from third terminal(check).for my card needs a common in addition to signal I used supply common for this .

for checking loop resistace hw I need to connect the multimeter ,is in sereis ?do I want to check capacitance also .....?if yes how ?series or parallel .....?

one more thing my transmitter having no error ...its local display is fine and sowsreading correctly....

please do give me a solution?

Have you read the manual? The "Check" terminal is used for external meters, not for sending the milliamp signal to your analog input. Connect it as I showed in the drawing and it should work fine.

Normally, you won't need to check the capacitance. You're not working with DC not AC so capacitance should not be too much of an issue.

You have connected your supply to the + and - terminals. Of course it will work. Unfortunately, you didn't connect the analog input properly which is why you're not getting a good reading. If you look at my drawing, you'll see that the transmitter and analog input card are in series starting from the 24V supply, into the transmitter, into the analog input and then to COM.

Read the manual carefully. Everything you need to know is there.

regards,

Vulcan

Hi mr. Ramdas I think insted of checking loop resistance you can check this..first of all if there is a error in the transmitter the display will indiacte Er 01 to 07 based on the type of the error like over range, chip problem, HP-LP reverse configuration etc. if there is a error u need to rectify it.

2) if you have "brain terminal"( yakogawa transmitter's communicator) you can communicate with the transmitter , check & correct configuratrion.

3)to check the loop either you can feed 4- 20 Ma to the input card through Brain terminal with transmitter connected in or disconnect the transmitter and feed 4- 20 ma from portable source and check the micrologix if u r geting correct input if your loop is ok, you need check with the transmitter

I work for a company that builds process skids, most of which have dozens of 4-20ma instruments. We use an Altek 134-2 loop checker to confirm instrument operation. Sometimes, if the skid does not contain the system processor, this is all we have to check operation before shipping. Excellent tool for such purposes. With three 9 volt batteries, it will power the instrument and show ma return if it is functioning, or can be configured to replace the instrument to allow checking of the input card. If you forsee checking instruments frequently, invest in one of these. They save time over rigging up the equivalent test circuit. (24VDC supply/ma meter)