Hooking up temp senor to PLC - Page 1
Forum section: electronics / beginners

author: Blackfield
author_rank: Newbie
timestamp: November 25, 2021, 06:39:50 pm
content: I've gotten my hands on some Allen Bradley PLC equipment and i'm trying to get in to it, but i need som help here.I've got this temperature sensorhttps://bdih-prod-assetcentralapi-assetcentral-rest-srv.cfapps.eu10.hana.ondemand.com/files/DLA/005056A500261EDAB08A8C6413EE94A9/BA01952TEN_0220.pdfand i have this PLC input Module (1794-IE8H)https://literature.rockwellautomation.com/idc/groups/literature/documents/um/1794-um063_-en-p.pdfThe io ethernet adapter is configured correctly in rslogix5000 and the module is powered by 24 v power suply.As i understand from the datasheet for the temp sensor I can hook it up with two wires to get a 4-20 mA signal. I've connected them to terminals 0 and 1 on the input module but i don't get any data for channel 0 in rslogix. Have i missunderstood something here? Do i still need to connect it to a wheatstone bridge or something like that?

author: Vtile
author_rank: Super Contributor
timestamp: November 25, 2021, 09:02:18 pm
content: Quickly using google it indicates you have analog voltage module. In case IIRC A-B it can be sinking or sourcing. You need to do more manual reading to give more specific details of module.If it is Sinking&sourcing variety you need to use IIRC HW config to set each channel to sink or source.Because you have mA transmitter you can not directly connect it to card with only voltage sink ability. You can go around that part by using ohms law and using resistor between channel terminals to get x to 10v from 4..20mA.Also you need to connect I/O cards +24v and ground (com) to get the card working.If your equipment is at mint condition you might want to sell them, as because chip-crisis some models are under the rock andprices for seller might be favourable. Ebay sells those 2nd preowned cards 1200-500 € + shipping at the moment.It seems I was falsely interpretting google result. It seems to be current input module, but anyway. One (not me, unless you pay for an hourly rate) needs to read manual to confirm it is not sourcing variety (assuming your transmitter is sourcing variety ... again not reading manuals for you) then according to manual you do wire everything and aldo check that HW config for module is correct. Screenshots might be helpfull.... and such get better answers faster.

author: Blackfield
author_rank: Newbie
timestamp: November 25, 2021, 11:07:33 pm
content: The hardware is configured correctly. The datasheets that i posted are all the documentation that is available and i thought that everything one would need to know would be in those two documents. I've read the datasheets through and through many many times and i still can't figure it out. The + and com power suply is wired as in page 51 in the datasheet of the input module. I connected it as indicated on page 18 in the sensor datasheet to terminals 0 and 1 on the input module as indicated on page 51 in its datasheet. Then there is also written on page 52 that terminals 0 1 2 are input 0 source, signal and return respectivly but the terminal 2 is not specified in the connection scematics pictures in the page above so i'm not sure what that is and googeling it didn't make me wiser. The only experince i have with tempsensors is with pt100-element in a wheatstone bridge to a mcu, and i don't really have any experince with this industrial stuff and 4-20 mA signaling, but since i had this opportunity i thought that I wanted to learn.

author: Manul
author_rank: Super Contributor
timestamp: November 25, 2021, 11:30:17 pm
content: First, are you absolutely sure you have 4-20mA version? There are also pt100 and "IO-Link" versions.

author: Blackfield
author_rank: Newbie
timestamp: November 25, 2021, 11:38:18 pm
content: It says " integrated transmitter (IO-Link and 4 to 20 m" in the datasheet so assume so

author: Manul
author_rank: Super Contributor
timestamp: November 25, 2021, 11:47:38 pm
content: There is version "with electronics" and without (pt100), I think it is different part numbers, but same datasheet.QuoteQuoteOnly you will know, you have the sensor.So you used two pin connection like below?

author: Blackfield
author_rank: Newbie
timestamp: November 25, 2021, 11:52:44 pm
content: It doesnt have any letter A B or C butbit says output io-link 4-20 mA on it. Yes i used that two wire connection.

author: Manul
author_rank: Super Contributor
timestamp: November 25, 2021, 11:58:40 pm
content: Ok, so take 24V (or 12V, or 15V, whatever you have) supply connect pin 2 to GND and pin 1 to +24V. Measure milliamps with multimeter. Is it in the range between 4 and 20 mA? Does it react to temperature change?

author: Blackfield
author_rank: Newbie
timestamp: November 26, 2021, 12:20:29 am
content: I will try that. But just so to make sure that im not completely missunderstanding the workings of theese devices. If hook up with two wires with some volage in the specified range between them the sensor should transmit some current in the 4-20 mA range proportional to the temperature. And the inputmodule shoud detect that current on if the "+" wire is connected to terminal 0 and the "-" wire is connected to teminal 1 for example. When i meassured there was 24v between terminal 0 and 1, which is what the powersuply gives.

author: Manul
author_rank: Super Contributor
timestamp: November 26, 2021, 12:34:34 am
content: Such 2 wire 4-20mA sensor will vary it's current consumption when powered. It's current consumption is the output signal.Keep polarity correct though.

author: Keivinstib
author_rank: Newbie
timestamp: November 26, 2021, 12:48:05 pm
content: All Ace PLCs with analog inputs (0-5V or 0-10V) can be used with this temperature sensor.For example, the Ace222V5 can use up to 12 temperature sensors !With our temperature sensor, we provide a pre-wired resistor of 10 kΩ.With 10 kΩ resistor you can work between -40 to 105 °C with 5 or 10 VDCNever apply more than 5 or 10 VDC (depending of your Ace PLC) on the analog inputs !We suggest to use :a Screw Terminal Board for connect your temperature sensors.a 5 VDC Power Supply for powered resistors and also the Ace PLC.