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analog signal interface

Created by: Johnluck at: 11/14/2012 11:24 AM (9 Replies)

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11/14/2012 11:24 AM	Rate (0)
Johnluck Experienced Member Joined: 3/29/2012 Last visit: 1/8/2025 Posts: 62 Rating: (0)	Please, can someone help me with this. I have two plant. i want the level on one plant to be display on the second plant HMI. I have run wire from one plant to another. I have unscaled the analog level signal on the first plant and I got my 4-20mA outputs which will be an input to the second plant. I scaled this 4-20mA signal on the second plant to the level i wanted to display on HMI which is 0-20000 but on monitoring the process on my programmer, the 4-20MA input signal from the first machine was not seen on the second machine, even though the $-20mA is physically present at the input. May be because I have different 24volts on each plant that is why I cannot process the signal from the first plant on the second plant. Does anybody know what i can do apart from using IP and PI converter to convert signal from the first plant to pressure first and then convert the pressure back to current using the 24v on the second plant. can anybody help me with what to do without the IP and PI converter. Thanks.
	johnluck
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11/14/2012 3:57 PM	Rate (0)
daad Silver Member Joined: 10/31/2011 Last visit: 11/26/2024 Posts: 400 Rating: (5)	Dear Johnluck, To apply potential on second PLC you have to synchronise zero volt of both side supply.Othr solution is to use signal isolatorhttps://www.automation.siemens.com/mcms/industrial-controls/en/control-devices-monitoring/schnittstellenwandler/pages/default.aspx?HTTPS=REDIR. Regards

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11/14/2012 4:30 PM	Rate (0)
Johnluck Experienced Member Joined: 3/29/2012 Last visit: 1/8/2025 Posts: 62 Rating: (0)	Thanks a lot. How can I get the part number for the interface converter SIRUS 3RS17 and secondly can you please assist on how to syncronise the zero volts of both panel. Thank you once again.
	johnluck
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11/14/2012 5:43 PM	Rate (0)
daad Silver Member Joined: 10/31/2011 Last visit: 11/26/2024 Posts: 400 Rating: (5)	Dear Johnluck, Here is model of analog signal isolator3RS1700-1AD00 and some other with similar specifications. 2nd answer is to sync zero by simply connecting GND of one module to other module.

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11/15/2012 9:48 AM	Rate (0)
Johnluck Experienced Member Joined: 3/29/2012 Last visit: 1/8/2025 Posts: 62 Rating: (0)	I got the part number yesterday. And on the zero volts syncronisation, i will say thank you so much. i will try that first, if it does not work then i will have to order the converter.
	johnluck
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11/27/2012 10:31 AM	Rate (0)
Johnluck Experienced Member Joined: 3/29/2012 Last visit: 1/8/2025 Posts: 62 Rating: (0)	i have try the zero volt syncronisation and I can monitor the level of one machine on the other now but there is a issue. The 4-20mA send from the first machine to the second machine was monitored and it was observed ranging from -327...to +327.... At exactly 16mA at the input of the second machine the reading has reached its maximum figure which is +327... so even when the level at the first machine has not reached its maximum, the level indicator on the second machine has reached its maximum. The level are not the same on both machine. I thought at 4mA i should have 0 at the input of the scaling not -327... and at 20mA i should have 27..... not +327.... Does anybody knows what is happening here and what I can do to handle this situation.
	johnluck
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11/27/2012 11:03 AM	Rate (0)
Atisim Posts: 8 Rating: (1)	Hi, You are right. you have to scale the 4-20ma signals properly, 4ma-0 and 20ma - 27648.hopefully your problem will be solved.
Atisim Posts: 8 Rating: (1)
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11/27/2012 3:13 PM	Rate (0)
Johnluck Experienced Member Joined: 3/29/2012 Last visit: 1/8/2025 Posts: 62 Rating: (0)	The problem I am actually facing is that despite the fact that i have 4-20mA at the PIW input the values i see at the input of the scaling fc FC105 is -32767 at 4mA and 32767 at 20mA. This is the value i want to scale to 0-20000. I know that FC105 do its calculation base on the following OUT = [ ((FLOAT (IN) – K1)/(K2–K1)) (HI_LIM–LO_LIM)] + LO_LIM* The constants K1 and K2 are set based upon whether the input value is BIPOLAR or UNIPOLAR. ·BIPOLAR: The input integer value is assumed to be between –27648 and 27648, therefore, K1 = –27648.0 and K2 = +27648.0 ·UNIPOLAR: The input integer value is assumed to be between 0 and 27648, therefore, K1 = 0.0 and K2 = +27648.0 If the input integer value is greater than K2, the output (OUT) is clamped to HI_LIM, and an error is returned. If the input integer value is less than K1, the output is clamped to LO_LIM, and an error is returned. now my input integer is greather than k1 which supose to be between 0 and 27648 and my output is at 20000. Another issue is that by the time I have 16mA at my PIW input, the scaling input value has already reached 32767. My question now is that what can I do to make the input reads between 0 and 27648 and to correspond with the changes in mA between 4 and 20 at the PIW word. The type of analog input module i am using is 2AI I 2WIRE ST (6ES7 134-4GB01-QAB0). Is there anything else i will do may be in the configuration or in the program to make me achieve my aim. Attached below is the snapshot of the scaling fc. thank you. Attachment C:\Documents and Settings\ngoyedelek\Desktop\siemen.zip (112 Downloads)
	johnluck
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11/27/2012 5:50 PM	Rate (0)
daad Silver Member Joined: 10/31/2011 Last visit: 11/26/2024 Posts: 400 Rating: (5)	dEAR jOHNLUCK, Without any deep search One option is to try to enable bibpolar bit of FC105 and it will give you same scalling. If still it persists then search again

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11/28/2012 12:10 PM	Rate (0)
Johnluck Experienced Member Joined: 3/29/2012 Last visit: 1/8/2025 Posts: 62 Rating: (0)	I think the bipolar bit will only have something to do with the output value range not the value I am getting at the input of the FC105.
	johnluck
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