convert 0-10v to 4-20ma

[OkiePC]

We had a plug in octal base version that was great for ease of replacement on a standard din rail relay socket. They were fairly reliable and accurate, but could be tweaked with pots on the device, so they were easily tinkered with, and subject to exceesive plugging/unpluggin in. They were great "uh-oh" fixers because you could set the zero and span, and install one in minutes.

My favorite stuff for rugged reliability came from Wilkerson. wici.com. These were a gold mine of rugged reliability. I only replaced one in ten years of over 20 installations doing frequency to voltage in some nasty old tire plant panels.

http://www.plctalk.net/qanda/newreply.php?do=newreply&noquote=1&p=256437

We used something along the lines of The DinMOD.

If you can read and set jumpers/dipswitches, you can R&R one too. Very Industrially friendly stuff.

$240 bucks one time..."UL recognized permanent warranty"

Look at the electrical isolation specs on that thing!
Paul

 

[curlyandshemp]

LOL I am sorry to tell you but it do work.

Do you want me to make you a drawing ?

But as Tom Jenkins mentions first check the output impedance first.

again OHMs Law.
I = E/R

there is no way 4 ma can be derived from 0V @ 500 ohms. I believe all math courses I ever took stated that 0 divided by anything equals 0

Yes , please provide your wiring diagram.

 

[lbg_dk]

there is no way 4 ma can be derived from 0V @ 500 ohms.

I am sorry but there do I say that ?

In message #7 i write 0-20mA

I know that is not 4-20mA. But if it is to an PLC with 0-20mA input then it is very easy to fix in code.

I have now read my post from #7 again. English is my second language. Did i write some thing there was not "english" ?

Yes , please provide your wiring diagram.

Do you still want me to make a diagram 0-10V to 0-20mA ?

 

[rdrast]

You are also assuming, that a 0-10VDC device can even SOURCE 20mA. Most voltage outputs simply cannot source that level of current at all.

I am sorry but there do I say that ?

In message #7 i write 0-20mA

I know that is not 4-20mA. But if it is to an PLC with 0-20mA input then it is very easy to fix in code.

I have now read my post from #7 again. English is my second language. Did i write some thing there was not "english" ?

Do you still want me to make a diagram 0-10V to 0-20mA ?

 

[Tom Jenkins]

This thread is a perfect example of needing to understand how things work, not just the mathematics.

Example: If it takes nine months for one woman to have one baby, how long does it take two women to have one baby?

Ohms law indeed says that you could get 0-20 mA from a 0-10 VDC output by calculating the right resistance, and you can draw a circuit diagram in conformance with Kirkhoff's (spelling?) Law to prove it. It just won't work in the physical world. Voltage outputs, as rdast states, are limited current output devices. They won't put out 20 mA or even 4 mA in most cases.

 

[orense]

4-20 mA problem

Hello,

I have a strange problem. We have 4 gensets on a oil rig. We use a 4-20 mA signal from a Woodward 2301D speed controller to send the load signal back to a Siemens s7 plc. I connected one of the signals, and it worked out great. 2 wires, powered from the speedcontroller. Set the Siemens analog input card to C on the dip switch. Everything worked, signal was acurate. I am using FC90 analog input in the program.

The I came to the next one, connected it the same way. this time the signal went straight to 32767, when connected to the speed controller. Even when I removed one of the wires it was still 32767. When I removed both, it went to -32768.
I removed the signal and used my loop calibrator. No problem, showed 0 at 4 mA.
The cable between them should be about 20-25 meters.

It seems to be overpressuring the whole signal or something, but I am reading 4 mA in the loop. It is really strange...

Are any of you specialists on 4-20 and knows what this might be??

reg
Andreas

 

[John Soltesz]

Hello,

I have a strange problem. We have 4 gensets on a oil rig. We use a 4-20 mA signal from a Woodward 2301D speed controller to send the load signal back to a Siemens s7 plc. I connected one of the signals, and it worked out great. 2 wires, powered from the speedcontroller. Set the Siemens analog input card to C on the dip switch. Everything worked, signal was acurate. I am using FC90 analog input in the program.

The I came to the next one, connected it the same way. this time the signal went straight to 32767, when connected to the speed controller. Even when I removed one of the wires it was still 32767. When I removed both, it went to -32768.
I removed the signal and used my loop calibrator. No problem, showed 0 at 4 mA.
The cable between them should be about 20-25 meters.

It seems to be overpressuring the whole signal or something, but I am reading 4 mA in the loop. It is really strange...

Are any of you specialists on 4-20 and knows what this might be??

reg
Andreas

I am thinking ground loop. But, is it a single S7 and same AI card? Did both inputs show 32767? Did you measure the second speed controller output? Can you try connecting the first speed controller to the second input? And the second speed controller to the first PLC input? I have not used an S7. Is the AI card an isolated input type?
If you have a ground loop you would need an isolator for each signal or go to an isolated input card.

 

[irondesk40]

thanks for assistance.

Have another question that relates to this.

What is the advantange of using a rtd or a thermocouple, or using a thermocouple over a rtd.

In the past, I have used mostly j type thermocouplers.

 

[krk]

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