Extending wires between Current Transformer and Panel Meeter help

Thread Starter

diebog

Joined Mar 23, 2013
223
No problem at all. I am still waiting on the meter to show up. Looks like this Thursday maybe. As far as hooking it up, it seems real simple and straight forward. Ill just have to play around with the software a bit to understand what does what.

I appreciate you checking in with me. I am very thankful for all your help!
 
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Thread Starter

diebog

Joined Mar 23, 2013
223
I finally got the Trumeter and spent some time configuring it with the software they have you download. But I have a few questions. Here are a couple data sheets http://truapm.com/wp-content/uploads/2015/03/APM-Quickstart-A3-Layout-PM-v1.1.pdf http://truapm.com/wp-content/uploads/2014/11/Process-Indicator-US.pdf



I pulled 24vDC from inside the panel where this is mounted, and connected those to the 12-24v DC PSU +-. So my question is how do I wire up the Current Transducer? Here are some data sheets on the CR Magnetics CR4220-50 I bought. http://www.crmagnetics.com/Assets/ProductPDFs/Developing Voltage From 4-20mA Current Loops.pdf
http://www.crmagnetics.com/Assets/ProductPDFs/CR4220-60 Series.pdf
http://www.crmagnetics.com/Assets/ProductPDFs/Developing Voltage From 4-20mA Current Loops.pdf
http://www.crmagnetics.com/Assets/ProductPDFs/Using the CR4220 Series Current Transmitter.pdf
http://www.crmagnetics.com/Assets/ProductPDFs/Developing Voltage From 4-20mA Current Loops.pdf

I realize voltage has to run through the CT and the drop is what the meter detects and then turns that into a number in retrospect to how it was setup. I set it up so 4-20mA=0-50 which is not actual amps but is just a number that's displayed. I was able to choose any 4 letter word so I put AMPS. I am just confused if I am supposed to wire the CT to the meter from the output or input on the meter? And on the CT there are 5 hookups If I remember correctly. Im pretty sure I just use the "+" and the "-" on the CT. So where does the voltage come from to flow from the Transducer to the Meter in the "loop" power? Am I going to need to tap into DC voltage where the CT is mounted? The data sheet for the meter said 0-10v if your using the Vinput. So I will need to step the 24v that the PSU inside the cabinet (where the CT is mounted) down to 10v, unless I am missing something.

Also the terminal "RST" on the meter is called a RESET in the data sheet, what is this for?




trumeter.png
 

Reloadron

Joined Jan 15, 2015
7,501
In this link which you posted they show the setup for the transducer. In that drawing your meter is what they call Instrumentation Resistance which is the I Input of your meter. Does that make sense to you?

Ron
 

Thread Starter

diebog

Joined Mar 23, 2013
223
Ya it makes sense to a point, but a few things I still am not clear on. The transducers data sheet says it needs 24v dc at 20ma. But the trumeter I bought, under the v input it's says 0-10v. So isn't that's saying to not input more than 10v in this loop?

And the transducer also says the total loop resistance (instrument plus wire) should not exceed 600 Ohms. On the trumeters data sheet under the impedance value it's says 100k Ohms for voltage and 15 Ohms for current. So doesn't that put me over right of the bat? Now adding the wires resistance would be even more. I used an online calculator for 100 ft of 18awg wire and it was over 600 Ohms. But when I phisically test the wires with one end tied together and using an DMM I get around .7 to 1 Ohm. 50 feet is a close guess on the length. If anything it's a few feet less than that. Am I missing something? Is this not going to work?
 

crutschow

Joined Mar 14, 2008
34,280
.....................
I used an online calculator for 100 ft of 18awg wire and it was over 600 Ohms. But when I phisically test the wires with one end tied together and using an DMM I get around .7 to 1 Ohm. 50 feet is a close guess on the length. If anything it's a few feet less than that. Am I missing something? Is this not going to work?
Your online calculator is way off.
This one gives a value of 0.639 ohms for 100' of 18AWG copper wire.
 

Reloadron

Joined Jan 15, 2015
7,501
Ya it makes sense to a point, but a few things I still am not clear on. The transducers data sheet says it needs 24v dc at 20ma. But the trumeter I bought, under the v input it's says 0-10v. So isn't that's saying to not input more than 10v in this loop?

And the transducer also says the total loop resistance (instrument plus wire) should not exceed 600 Ohms. On the trumeters data sheet under the impedance value it's says 100k Ohms for voltage and 15 Ohms for current. So doesn't that put me over right of the bat? Now adding the wires resistance would be even more. I used an online calculator for 100 ft of 18awg wire and it was over 600 Ohms. But when I phisically test the wires with one end tied together and using an DMM I get around .7 to 1 Ohm. 50 feet is a close guess on the length. If anything it's a few feet less than that. Am I missing something? Is this not going to work?
This is what things should look like:

Tru Meter Connect.png

Your meter allows for either a voltage input of +/- 10 Volts or a programmable current input. You will program the meter for a 4 to 20 mA current input. The current sensor outputs a 4 to 20 mA current loop and that is what the meter is reading. The voltage input impedance has nothing to do with any of this. Using the software for the meter you will program it so 4 mA = 0 Amps and 20 mA is whatever the full scale current is. I forgot the sensor range? :( Also, if we run multiple loops through the current transducer primary that needs considered as to full scale current for 20 mA. The RST on the meter is likely an external reset pin. Pretty common. Yes, this will work just fine.

Ron
 

Thread Starter

diebog

Joined Mar 23, 2013
223
That's makes more sense now. As far as the primary loops, I thought you said before to stay with 3 loops? Should I try it with one loop, or just go with 3.

And the sensor is 50amp rating.
 

Reloadron

Joined Jan 15, 2015
7,501
You know what I would start with a single pass through the sensor. So 4 to 20 mA is 0 to 50 Amps. Then if the motor current is always below 25 amps for example I would run a second loop for the primary. Then 4 to 20 mA is now 0 to 25 Amps. Glad it made more sense with the added cartoon. :)

Ron
 

Thread Starter

diebog

Joined Mar 23, 2013
223
The motor peaks at 50 or so amps right at start up and then with no load it's around 7 amps or so. And whith normal load I always kept it below 20 amps per the manufactures suggestion. Now this was all according to the old meter that originally came with this equipment. So those are probably not exact numbers. So I guess I should go with 2 loops sense it will always be below 25 amps? Or are you saying if the meter doesn't show more than 25 amps when it should be (like at startup) then I should add a loop?

I probably should just mess around with it then keep asking questions. :D
 

Reloadron

Joined Jan 15, 2015
7,501
I believe you covered it well here:
I probably should just mess around with it then keep asking questions. :D
Just set it up and let's get things workig and then see what we have. :)
Leave yourself enough slack in the main current carrying conductor to loop it as needed. This ne current sensor will work much better than the old system and offer up improved accuracy.

Ron
 

Thread Starter

diebog

Joined Mar 23, 2013
223
I got everything hooked up and turned the power on and right away the meter tabs out acting like the max current has been reached. So I checked everything and it's all hooked up right, so I looked into the software again to make sure I didn't have something configured wrong and it's set for current and 4-20mA equals 0-50 amps and besides changing brightness, how fast it reacts and 2 alarm modes that can be set, there isn't any other options. Looking through the data sheet again, I think that the max current working voltage of 1.5 has to do mean something. I know you said it didn't have any effect here, but what else would cause the meter to read max when the motor isn't even running?

Even when I turn the motor on, nothing changes on the meter. My guess is because it's already showing the max. So what am I doing wrong? I tried 2 wraps of the primary, I ran them through he opposite way just incase I had them backwards, but no change. I made sure 24v was going through the CT. The meter only will go back to zero when I remove the positve input which is the negitive out from the CT. When I touch the wire back on the terminal it jumps rigt back up to max. So the meter is working, or at least the numbers are moving and it is measuring something.

I also checked he CT pos and neg terminals with nothing connected for continuity and there was none. But when I have everything connected and turned on, there is continuity betweent those two terminals. This probably means nothing, just figured I might find something like maybe the CT is bad or something.

I've got so much time and money invested in this, I have to find a way to make it work. Any ideas?
 

Reloadron

Joined Jan 15, 2015
7,501
If you have a meter that measures mA and most hand held DMMs do I would break the current loop and place your DMM in series with the current loop and see how much current is running through the loop. Also, I know you say it is setup and wired correctly but check it again. Actually you can disconnect the current loop from the meter and just place your DMM in there and measure the loop current. With nothing happening you should be seeing 4mA on your DMM. Let me know what you get.

Looks to be programmed correctly. I would only use 1 decimal place but it looks fine.

Ron
 

Thread Starter

diebog

Joined Mar 23, 2013
223
Ill check that tomorrow with a DMM.

So this figure below of 1.5v has nothing to do with what I am doing right?
data sheet.png

But then on this one where the red lines are it says 24v max
data sheet 2.png
 

Reloadron

Joined Jan 15, 2015
7,501
The dip switches apparently set the input, you want a current input. The max current input is 50 mA and the input impedance for current in 15 Ohms. As to the red 24 volts you labeled that is just telling you the Outputs are Open Collector 24 Volts MAX. Nothing having to do with what you want. We are not using the outputs.

As to the 1.5 volts you are seeing? The Current Input has a 15 Ohm impedance. You are running a current loop through that input. The max current is 50 mA (even though we are using 20 mA max). So what you get is .050 Amp * 15 Ohms = 0.75 Volt maximum across those terminals. They are only telling you that the Max is 1.5 Volts which we never see with a 4 to 20 mA loop. My guess is you have something incorrectly wired, we will find it. The only way the meter can over range is with an excessive input. This stuff is not difficult, believe me.

Make sure the switches are set for a current input and we know the software is set for 4 to 20 mA.

Ron
 

Thread Starter

diebog

Joined Mar 23, 2013
223
I guess I am still confused about the 24 volts that are bing input into the CT. So if 24v goes through the CT and to the meter, wouldn't it be 24v across those terminals? With both pos and neg disconnected from the current input on the meter I get 24v dc on those two wires. So that's where I am getting confused about the max working voltage of 1.5v for the current input.

And as far as the dip switches go, the data sheet says with all 4 in their off position its setup for custom defined in software program. So they shouldn't have any effect on this. I checked them and they are all in the off position.

With it all hooked up I have right at 21vdc across the terminals
 
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Thread Starter

diebog

Joined Mar 23, 2013
223
I checked the mA with 2 DMM and with the wire coming from the CT disconnected I am getting 5mA to ground. And 1.7mA to the + terminal on the back of the trumeter (where the wire was disconnected from) which is apart of the current loop through the trumeter and it does the same thing, maxes out the display to 50amps. As soon as I remove the wire the display on the trumeter goes back to zero.
 

Thread Starter

diebog

Joined Mar 23, 2013
223
Another test I just did was with one primary wrap and with the DMM hooked up to the CT and ground I got 23ma at startup and 7ma running with no load. Then when shut down it went down to 4.8 or so ma. With 2 primary wraps it went to max of around 30mA at startup and 9mA running no load. 3 wraps I got 24mA and 11.5 running no load.
 

Reloadron

Joined Jan 15, 2015
7,501
I guess I am still confused about the 24 volts that are bing input into the CT. So if 24v goes through the CT and to the meter, wouldn't it be 24v across those terminals? With both pos and neg disconnected from the current input on the meter I get 24v dc on those two wires. So that's where I am getting confused about the max working voltage of 1.5v for the current input.

And as far as the dip switches go, the data sheet says with all 4 in their off position its setup for custom defined in software program. So they shouldn't have any effect on this. I checked them and they are all in the off position.
The below is what you have:

CR4220 Current Transducer.png

You have a VDC of 24 volts in series with the current transducer. The current transducer outputs a current into the loop. The 15 Ohm resistor is your meter input resistance and is part of the loop. The loop current is 4 to 20 mA. There isn't much to this and these are very common circuits. Configured as above across the meter terminals you should measure between (4 mA * 15 Ohms = 60 mV and 20 mA * 15 Ohms = 300 mV). The only way this can't work is if it is wired wrong. If you just measure the resistance across the current input to the meter with the meter Off you should see about 15 Ohms.

Ron
 

Reloadron

Joined Jan 15, 2015
7,501
Another test I just did was with one primary wrap and with the DMM hooked up to the CT and ground I got 23ma at startup and 7ma running with no load. Then when shut down it went down to 4.8 or so ma. With 2 primary wraps it went to max of around 30mA at startup and 9mA running no load. 3 wraps I got 24mA and 11.5 running no load.
Start with a single pass. With no current the loop should be 4.0 mA. With current, the motor running, you will obviously see above 4 mA.

Ron
 
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