Shortcuts in troubleshooting 1

[DmanD]

Hi All,

Please, suggest for troubleshooting circuits having different types of sensors e.g. fluid level, proximity, limit switch etc.;output going to relay which sends 24V input to PLC.

Also how to troubleshoot the 2 point or 3 point sensors with power ON or OFF.

Thanks,
D'man

 

[itsmoked]

Generally you get the manual for the sensor of interest and a voltmeter. You make sure the sensor is provided with its proper excitation voltages and then you measure the output. Make an estimate from the manual of what you would expect and if it is close move on to the next sensor. If the sensor is an on/off sensor try to do something to place it in its next state, like advance the conveyor a little. For a temperature sensor you might want to raise or lower the temp and make sure the sensor's output moves in that direction.

I don't know what you mean by a 2 or 3 point sensor...


Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[automatic2]

Divide the circuit between inputs and outputs. On the troubled half, check that supply power is stable. Then check that it's output has relation to it's input stimulus. You may have to isolate the device to confirm.

 

[nbucska]

D'man


Plesae read FAQ240-1032
WEB: <

http://geocities.com/nbucska/>

 

[DmanD]

Dear all,
Thanks for your replies. I am quite specific in my querry. I need to test the proximity sensors and magnetic switches in emergency like situations. The original manuals have not been preserved by great people who knew all. I have only a multimeter and electrical common sense at my disposal.Thats why I was asking for shortcuts in testing these.

Anyway I got some ideas.

Thanks a lot
D'man

 

[nbucska]

d'man
Specific == well defined. To be "specific", please list the
sensors by maker and type ( they have to be tested, too !)

You mention "different type of sensors" and (one )
output. How are the many outputs combined or selected
into one output?

What is the whole DUT ? can you describe how it is
suppose to work?




Plesae read FAQ240-1032
WEB: <

http://geocities.com/nbucska/>

 

[waross]

Hi D'man
Often a quick and easy test depends on the application. For instance, a proximity sensor may be easy to test on the bench with a piece of scrap steel. It is more challenging to test if it is screwed into a hole in a flywheel housing and is counting passing gear teeth. Even if the proximity detector is in perfect condition the application will fail if the spacing is not correct and the spacing cannot be measured direectly.
The more information you can provide us the better will be the quality of your answers.
yours

 

[nbucska]

Waross: this is what I am trying to explain in my FAQ

ALL:
Do you know any way to make people read a short FAQ
instead of wasting our time ?



Plesae read FAQ240-1032
WEB: <

http://geocities.com/nbucska/>

 

[itsmoked]

Hi nbucska.

While I find your FAQ to be totally true... I think it is too subtle with respect to these poor questions. I think if posters are too dim to "up front" ask clear questions while providing suitable detail then they are not going to make the connection in your FAQ with a discussion about units and decimal point creep. I think you need a clearer "provide us details about your project" aspect to your FAQ.. I would leave your present FAQ for the specific use of decimal creep and write a new one striving for "brief".


Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hi nbucska
I thought your faq was well done. Thanks.
I understand your frustration. I find that part of the challenge of Engineering Tips is overcoming the various "people problems" we face.
One of these people problems is poor English language skills by someone who may be an excellent engineer or technitian but unfortunately speaks English as a second, or fourth language.
I'm in a Latin American environment where sharing or volunteering information is apparently not part of the culture. I know your frustration, I face it on a monthly basis face to face with clients and it's hard to stay cool.
I think the appropriate responce on our part is to ask leading questions to elicit the needed information.
Your experience and knowledge are obvious by the quality of your usual replies.
respectfully

 

[Ashereng]

Your FAQ is a good example.

Getting someone to read something is difficult. Even after reading it, getting them to follow it is more difficult.

Unfortunately, people disregard rules, advise and good examples for various reasons.

Maybe a topic for a new post?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[DmanD]

Hi,
1.The proximity sensor is a PepperlFuchs make 230Volt sensor with a maximum sensing distance of about 15mm. I have got 10 pieces of these. All show correct result while in workshop but fail in the crane(workplace).
2.The liquid level sensor gives the output to Phoenix miniature relay which sends an input to 24V PLC. The PLC output should cut OFF a 440Volt Power supply when the LIquid level sensor senses high level. This is not happening. And I have not much of an idea how to test this circuit.


I hope the information will be of some help.

Thanks,
D'man

 

[GTstartup]

These work pretty well for testing installed prox switches.

http://www.suns-usa.com/st-800.htm?gclid=CPK2p-rYoIQCFUOLOAoduWGZgA

BTW in my experience failed prox switches can be attributed to two causes:

1. Incorrect Gap

2. High Temp

 

[waross]

I agree with GTstartup;
Check your gaps and wiring. Make sure that the polarity is correct.

great people who knew all

I have seen such people deliberatetly change the wiring colours several times in a conductor run. It may be well to use another conductor or use the ground to verify the continuity of the conductors. Also, when the proximity sensor is in place on the crane, test it with a piece of scrap iron. If it works in the field the problem is probably the gap. If it works in the shop but not in the field, see my comments about wiring.
When we get the proximity sensors working, we'l try the others.
yours

 

[DmanD]

Ya you are very correct - wiring was the problem. I had a nice workout in testing all the wiring done. The downtime and cost involved are also big. It will go down the company history as a legend.

I am going for the fluid level sensor with the same gameplan. But it is proving more difficult due to lack of space. Also shorting the two terminals of the fluis sensor is not giving any result at the relay.

Thanks a lot
D'man

 

[Skogsgurra]

To say the truth. I was only confused by that FAQ and I cannot see how it would have helped in this case - or several other cases.

I am not sure that I should say this again, but here goes: Use SI. That takes that kind of problems away.

Gunnar Englund

http://www.gke.org