Plc

I am getting a 2E-1 on my reading from a gas detector the gas detector checks out good but the 2E-1 stays on. Does this mean there is a error or is the PLC is not communicating with the detector and what can I do to eliminate this to be able to get the reading from the detector. None of the other detectors show this on the screen. they are reading correctly. i have general monitors smart sensors gas detectors. the transmitters are reading 0% lel. combustble gas detectors. but at the computer screen we are getting 2E-1 readings on one head and drifts from 2E-1 to 7E-1 on another. we are try to find out what 2E-1 means. thanks for any help.

We're gonna need a whole lot more information than that to be able to help you.

What kind of gas detectors? What does a 2E-1 mean??
How are they interfaced to the PLC?

i edited my question. thanks for any advice

OZEE said:

We're gonna need a whole lot more information than that to be able to help you.

What kind of gas detectors? What does a 2E-1 mean??
How are they interfaced to the PLC?

Click to expand...

When I go to the General Monitors website I find several different sensors -- I can't guess which one you're using, sooo....

How are they connected to the PLC? Are they on some kind of a bus (ethernet, devicenet, controlnet, profibus, ...) or are they discrete IO (On/Off = Good/Bad)??

Again, not knowing anything about your sensor, I would guess that 2E-1 floating to 7E-1 would indicate a 0.2 - 0.7 reading of whatever it is sensing, but that's merely a guess...

it is general monitors smart sensor the gas head model is 10001-1.

i am not sure what the plc is i am a gas technician and i only know as far as the heads are. on my end i am reading the heads are good put the operators on this platform tends to think my detectors are shutting them down. and i think other wise but i am trying to find info on the plc to explain that it is in the plc it is a input/output plc.

it is s4000c gas monitors.

they go to a terminalbus than from termal bus to plc i get them to the terminalbus and sombody already had them to the plc from there.

the plc is a plc5

the s4000c is the monitors and the plc is plc5 and the monitors go back to a terminalbus than from there to the I/O module. of the plc

OZEE said:

When I go to the General Monitors website I find several different sensors -- I can't guess which one you're using, sooo....

How are they connected to the PLC? Are they on some kind of a bus (ethernet, devicenet, controlnet, profibus, ...) or are they discrete IO (On/Off = Good/Bad)??

Again, not knowing anything about your sensor, I would guess that 2E-1 floating to 7E-1 would indicate a 0.2 - 0.7 reading of whatever it is sensing, but that's merely a guess...

Click to expand...

Here is a link to the manual.

Without knowing exactly how it's communicating to the PLC, it's kinda hard to know how to help.

This unit can use either relay-closures to indicate the status to the PLC or either a 4-20ma signal or Modbus to indicate the lel.

It's three different troubleshooting techniques... We might have to see the PLC program to be able to give you some better clues.

we don't have a program that is somebody else. but thanks for the help so far. lot of questions already answered.

A wild guess, but the 2E-1 and 7E-1 are probably floating point numbers in scientific notation. 2E-1 would be 0.2 and 7E-1 would be 0.7

This could be zero drift on the transmitter, an improperly configured input channel, an bad input card, or any number of things.

This probably calls for an onsite investigation by someone with expertise in the PLCs.

that is what i was thinking that it had somthing to do with the programming and the plc but my lack of experience with the plc gave me doubt. i was thinking a relay in the modbus of the I/O was going bad if their is one or the plc programming is bad. becasue my gas detectors and transmitters are good.

The Modbus, for a "crude illustration", really doesn't have relays -- it's a digital protocol that shares alot of information regarding the sensors - though in this application it's just a constant feed of the lel.

One question I always like to start with -- Has it worked in the past? If so, what changed?

If it never worked right historically, then it's likely a config problem. Even if you've just changed the unit out from one that did work in the past, it could still be configured differently (specifically comm configuration)

If it used to work then we know the PLC code is working. Unless someone has intentionally changed the program, it did not change itself. If it used to work, the PLC code still works.

Now it isolates the problem to something between the sensor and the PLC -- the cabling. Modbus is a coax. If it's modbus, it needs to be terminated on both ends of the network. Are all of the connections tight? What gas are you dealing with -- it may be corrosive and may have damaged connectors or conductors...

The other piece in the middle is the comm card in the PLC -- what is it? Are there any lights flashing? Are there any red-lights? Anything that looks like an alarm?

Can you manually make an alarm happen on one of the other sensors and the PLC knows about it? If that's the case, then the cabling is good, the plc is good -- it's something related to the sensor...

Just some ramblings... Hope it helps...