OT: Measure & Log resistance

Xsailor · Mar 10, 2010

Hi All,
We make medical devices and a recent request from a major client is to measure & log DC resistance values of each device.
I was hoping to do this online on the machine itself.

The machine makes about 7200 parts an hour. The idea is not to 'measure' the value but rather create a GO/NO GO kind of validation.

As a start, I am looking at 100 ohms - Parts above 100 oms will be marked and rejected (No GO).
I have the pneumatic actuator ready but was wondering which measurement 'style' will be most efficient & reasonable as I will have to retrofit about 14 stand-alone machines.

A few spare inputs/outputs are available on the S7 200 which controls the machine (Transistor Outputs).

Hints, Please.

Thanks
Xsailor

leitmotif · Mar 10, 2010

Xsailor said:
Hi All,
We make medical devices and a recent request from a major client is to measure & log DC resistance values of each device.
I was hoping to do this online on the machine itself.

The machine makes about 7200 parts an hour. The idea is not to 'measure' the value but rather create a GO/NO GO kind of validation.

As a start, I am looking at 100 ohms - Parts above 100 oms will be marked and rejected (No GO).
I have the pneumatic actuator ready but was wondering which measurement 'style' will be most efficient & reasonable as I will have to retrofit about 14 stand-alone machines.

A few spare inputs/outputs are available on the S7 200 which controls the machine (Transistor Outputs).

Hints, Please. Thanks Xsailor

You gave two different criteria
1. Measure and log
2. Measure and use for go no go with I assume no logging.

Another concept
measure
record to a buffer
take data from buffer and use it to print a label with the resistance value on it
stick label on product.

This way customer knows that you took the reading and when it comes time to service / calibrate etc in his shop they have a factory resistance value to work with.

Dan Bentler

Xsailor · Mar 10, 2010

Thanks Dan.
Good idea - but at 7200 pcs an hour, I might want to skip the labeling.

Any tips on the measurement - Does a voltage divider circuit sound silly?

Thanks for your help

Bobbias · Mar 10, 2010

Without any real knowledgeon the testing and such aspects, it certainly sounds electrically feasible. You could check the output voltage from the divider circuit and be able to tell how far off the tested resistance is from what you wanted, and use the difference to trip a GO/NoGo.

That would require an analog input though.

As for a digital way of doing it, I'm not sure what you could do.

kamenges · Mar 10, 2010

Something like this or one of it's cousins, maybe?

Keith

OT: Measure & Log resistance

Xsailor

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leitmotif

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Xsailor

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Bobbias

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kamenges

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