Analog output or 4-20mA from Scada Vs Fluke DC handsheld Vs Remote

Hi,

I am having actuator 240 V, that can take analog output of 4-20 mA signal.

Case 1, Fluke 4 to 20 mA battery operated 6V
it is very stable, no drifting

Case 2, A PLC 4 to 20 mA simulated by 24 V

It shows when the actuator go to the last position, it keep on drifting forward and backward

Current measure with Multi-meter shows consistent current reading. However the Voltage seems higher at 8 mA about 22 Volt.

Case 3, use another source using Potentiometer to generate 4-20 mA 24 V,

It is stable, no drifting
the voltage at 8 mA is 16 Volt.


We checked the mA using Fluke multimeter, all constant. What could be possible caused the drifting on case 2 .

You are probably overlooking some requirements for the actuator analog control inputs, e.g. related signal grounding. Can't be answered without complete information about the actuator.

Current measure with Multi-meter shows consistent current reading.

Click to expand...

Did you also check for possibly superimposed AC current?

Hi,

Enewbie said:

Hi,
...
Case 2, A PLC 4 to 20 mA simulated by 24 V
It shows when the actuator go to the last position, it keep on drifting forward and backward
Current measure with Multi-meter shows consistent current reading. However the Voltage seems higher at 8 mA about 22 Volt.
...
What could be possible caused the drifting on case 2 .

Click to expand...

You need to describe how you simulate the 4 to 20 mA by 24 Volts in case 2 for your question to be answered.

--Akanimo.

FvM said:

You are probably overlooking some requirements for the actuator analog control inputs, e.g. related signal grounding. Can't be answered without complete information about the actuator.


Did you also check for possibly superimposed AC current?

Click to expand...

FvM said:

You are probably overlooking some requirements for the actuator analog control inputs, e.g. related signal grounding. Can't be answered without complete information about the actuator.


Did you also check for possibly superimposed AC current?

Click to expand...

The actuator is to drive the stroke for increase and decrease the stroke so pump flow would increase/ decrease

This is the Service manual
https://www.dropbox.com/sh/pg4uofh3dycu0ul/AAAbasgleLxJqM3lOP0EHkxba?dl=0

This the measurement of the mA local ( stable) vs Remote (not stable) through same cable.

https://youtu.be/c8cHpQ7Q22Y

This the switching local to Remote through same cable when motor not running

https://youtu.be/OSb5En0Jba8
https://pulsa.salesmrc.com/Details.aspx?ID=3110

Akanimo said:

Hi,


You need to describe how you simulate the 4 to 20 mA by 24 Volts in case 2 for your question to be answered.

--Akanimo.

Click to expand...

it is by Ac to Dc 24 V converter simulate the 4-20mA from PLC scada

- - - Updated - - -

According to the board of the actuator


"It would provide approximately 160 ohms of resistance to a current loop. It will also accept voltage
signals in the 0-4 volt DC range. The Analog Input is electrically isolated from all other inputs,
outputs and earth ground"

160 Ohm is input impedance, anyone can enlighten this ?

If we are generating the 4-20mA, correct me if I am wrong, as I try to measure the voltage in the input signal it it does varies at high at 20mA and almost 0 at 4mA.

R= 160 Ohm
V= I. R

I= V/R

I constant
if we are sending 20 mA flow through a 160 Ohm, V = I.R = It would drop 3.2 Volt

if we are sending 4 mA flow through a 160 Ohm, V = I.R = It would drop 0.64 Volt

Therefore, 4-20ma through a 160 Ohm resistor will drop 0.64 to 3.2 V


Does the voltage is critical in mA and shall I make sense on the voltage reading in order to troubuleshoot this

Hi,

I've read the thread a few times. To be honest I can't find out what you descripb, what are the three cases for, what you want to achieve and where the problem is.

Maybe a simple sketch could help to clarify...

Klaus

it is by Ac to Dc 24 V converter simulate the 4-20mA from PLC scada

Click to expand...

Still unclear how you are generating a constant DC current with an AC/DC converter. What do you particularly mean with "simulate" in this regard?

FvM said:

Still unclear how you are generating a constant DC current with an AC/DC converter. What do you particularly mean with "simulate" in this regard?

Click to expand...

I am using a 4 to 20mA current loop which is sending via remotely by Scada, from the power source of 24 Volt.

It is just sending the signal 4 mA and the actuator would rotate Clockwise to 0 % where 20mA, the actuator would rotate counter clockwise to 100 %



What we suspect there is interference in the 4-20mA input, how we can identify the rootcause

Enewbie said:

Hi,

Case 3, use another source using Potentiometer to generate 4-20 mA 24 V,

It is stable, no drifting
the voltage at 8 mA is 16 Volt.


We checked the mA using Fluke multimeter, all constant. What could be possible caused the drifting on case 2 .

Click to expand...

From case 3, it doesn't seem like the current and voltage should have any linear relationship since 8mA is 25% and 16V can only be 25% if 13.333V is 0%. Moreover, it wouldn't have worked with a 6V calibrator. I wouldn't really bother about voltage except it is out of bounds.

Like you said, it may be interference.
Reaffirm that you have followed "Installation guidelines for EMC compliance" as listed in the ECA datasheet.

**broken link removed**
picture of "Installation guidelines for EMC compliance."


--Akanimo.

Akanimo said:

From case 3, it doesn't seem like the current and voltage should have any linear relationship since 8mA is 25% and 16V can only be 25% if 13.333V is 0%. Moreover, it wouldn't have worked with a 6V calibrator. I wouldn't really bother about voltage except it is out of bounds.

Like you said, it may be interference.
Reaffirm that you have followed "Installation guidelines for EMC compliance" as listed in the ECA datasheet.

**broken link removed**
picture of "Installation guidelines for EMC compliance."


--Akanimo.

Click to expand...

Anyway to confirm or for me to understand the source of interference or any tools that can measure.

I think i might be wrong as i am using fluke 789 processmeter to create analogue 4 to 20ma. It is stable. It used 6 Bolt battery like photo.

I really no idea why there is noise.
Btw ur attachment unable to open.

Take a look at the "Installation guidelines for EMC compliance." section in the ECA manual you attached.
I think it is on page 8.

I just snipped and attached that section. Sorry that it is not opening.

Akanimo said:

Take a look at the "Installation guidelines for EMC compliance." section in the ECA manual you attached.
I think it is on page 8.

I just snipped and attached that section. Sorry that it is not opening.

Click to expand...

Hi Akanimo,

I am not able to open the attachment, My interference seeemed coming from VFD to the analog signal input