I have a PLC 5 with a 1771-IFE analog input. I have a temperature transmitter wired to it. It converts 1000 ohm RTD signal into an analog output and has a range of -58 to 122 F. I am not sure what instruction(s) to use in my logic to get a farhenheit reading, which I will display on an HMI using Factory Talk. I tried a CPT instruction in which I multiplied the output value with a max range and divided that by 4095. No luck. I tried different max values with no luck. Thanks for any help. I am not a trained programmer, just an electrician moonlighting.
PLC 5 temperature logic
- Thread starter wstrizic
- Start date
bernie_carlton
Lifetime Supporting Member + Moderator
Assuming you mean that an input of 0 - 4095 represents -58 to 122 F then use the following
Farhenheit = ((Input * 180) / 4095) - 58
Farhenheit = ((Input * 180) / 4095) - 58
Thanks for your reply, bernie. I'm trying to install a 1000 ohm platinum RTD temperature transmitter. It has a range of -58 to 122 deg. F (-50 to 50 deg.C). I tried to calibrate the transmitter with the appropiate resistors, 803 ohm for -58 and 1193 ohm for 122, by adjusting the zero and span but I'm not getting anywhere. When I adjust the small resistor zero as low as I can, I get raw data of -336 on the analog card. When I use the bigger resistor and adjust the span as high as it will go, I get a raw data of 3000 on the analog card. Shouldn't I be getting 0 and 4095 respectively? I figured I just needed the right ladder logic to manipulate the raw data correctly but no luck so far. I've tried many different things with no success, including trying to get the correct celsius reading first. Thanks for any help you can spare.
xC0MMAND0x
Member
Why are you setting 803 ohm to -58 and 1183 ohm to 122?
Can you look at the raw input value (0 - 4095)?
0 *should* correspond to the low end (-58°F) and 4095 *should* correspond to the high end (122°F).
A total change of 177°F.
4095/177 = 0.043223443° (change per raw change)
So, the temperature in °F would be:
(0.043223443°)*(raw_input)-(55°)
Examples:
RAW INPUT / TEMPERATURE
0_________-55
100_________-50.67765568
200_________-46.35531136
300_________-42.03296703
400________ -37.71062271
500_________-33.38827839
600_________-29.06593407
700_________-24.74358974
800_________-20.42124542
1000________-11.77655678
2000________31.44688645
3000________74.67032967
4000________117.8937729
4095________122
Last edited:
Mickey
Lifetime Supporting Member
When calibrating a temperature transmitter you monitor the milliamp/voltage output and adjust it.
Forget about the PLCs raw data the milliamps/voltage need to be right first.
Can you tell us the brand and model number of your transmitter?
The transmitter may not have the adjustable range you want, check its specs.
How is the 1771-IFE configured voltage? current? range? jumper placement? software configuration?
Forget about the PLCs raw data the milliamps/voltage need to be right first.
Can you tell us the brand and model number of your transmitter?
The transmitter may not have the adjustable range you want, check its specs.
How is the 1771-IFE configured voltage? current? range? jumper placement? software configuration?
Last edited:
you sure you've configurated the analog board before?
I know if you are using the analog board 1771-ife, at first you must use the BTR and BTW function to get all information you need, check the attach.
In BTW I put the config vals. in N7:20 and I get results with BTR in n7:100.
I know if you are using the analog board 1771-ife, at first you must use the BTR and BTW function to get all information you need, check the attach.
In BTW I put the config vals. in N7:20 and I get results with BTR in n7:100.
The formula I ended up using is ((raw input/256)*11.25)-58. 256 being 4095/16 and 11.25 being 180/16. 16 being 20-4mA of course. I also had an issue with my power supply which turned out to be a wiring oversight. Thanks for all your help and suggestions!!
Similar Topics
Dear all,
I have below mentioned items,
1. Delta PLC DVP24Es2
2. Delta Thermal Module DVP 04TC-E2
3. Thermocouple Type J
Now i need to...
Hi everyone, Im planning to replace existing temperature controllers with a PLC.
The setup will be aprox 8 thermocuples, and the outputs are 8...
Hi;
I have installed a temperature and humidity sensor Autonics THD-R-C which gives 4-20mA signal out. The signal is connected with Fatek...
Hi All,
I need to get the temperature output from my sensors as an input to the PLC, and then run a linear actuator. The temperature sensors will...
Good day all,
i have a sensor, which is a dual humidity and temperature sensor.
I want to be able to connect this to a plc(probably Alen...