Ph to PLC
- Thread starter dontknow
- Start date
Tom Jenkins
Lifetime Supporting Member
You can always get a voltage signal out of a current signal by using a dropping resistor acrposs you input terminals. This is a 250 Ohm resistor that will produce 1-5 VDC at 4-20 mA current passing through it. Then you just have to use your programming to accommodate the 20% offset of 1 VDC in the input signal. You loose a little resolution, but the anaolg to digital conversion is going to be an order of magnitude more accurate than your pH probe anyway.
Ty for you're reply,
So if i use a 250 ohm resistor i will be able to see the values on the PLC?
only there is one problem.
my probe got a BNC connector. So how am i going to use a resistor and connect it to the PLC when im not permitted to destroy the BNC connector
Ty,
can the S7-1200 PLC read a value from 4-20mA?
I dont know how to find out.
or does it need to be converted to 0-5V?
nonuke
Member
- Join Date
- Sep 2005
- Posts
- 840
We use a lot of times the S7-1200 but we always configure the analog Input as a 0-10V signal and we use the 499 ohm resistor.
If you buy a PH probe, you will also need the PH transmitter to connect the probe to.
If the transmitter has a 0-10V signal output, you don't need the resistor.
If you buy a PH probe, you will also need the PH transmitter to connect the probe to.
If the transmitter has a 0-10V signal output, you don't need the resistor.
Ty,
do you know some good Ph Transmitters?
im searching atm but i cant find a good PH transmitter.
and what is a regular price for a PH transmitter?
nonuke
Member
- Join Date
- Sep 2005
- Posts
- 840
I think you should buy the transmitter from the same brand as the probe. It will be easier with the scales, connections etc.
What is the make and ref. of the probe?
I only know that the probe comes from applikon
and it was made in the USA, hopefully you can find something!
Probe guess. Contact this company in Germany for help with a selecting a signal conditioner.
ChrisWOvivo
Member
Isn't that a process monitoring / sampling instrument?
Usually pH probes are pipe mounted in-line, sometimes under a dome style housing.
How do you mount your probe in the process flow / substance to be measured?
Manual for probe.
PHTX-014 from Omega Engineering. Do you have an RTD for temperature compensation? Readings will be off if temperature of the liquid changes.
Use a 1000 Ohm RTD.
Link to manual for PHTX-014.
pH reference info from Omega.
PHTX-014 from Omega Engineering. Do you have an RTD for temperature compensation? Readings will be off if temperature of the liquid changes.
Use a 1000 Ohm RTD.
Link to manual for PHTX-014.
pH reference info from Omega.
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