On Fri, 27 Aug 2010 18:30:28 -0400, Wes
wrote:

Gerald Miller wrote:

I don't have that problem. I show up and the machine starts working which frustrates the
person that called me.

Wes
To the point where they don't want to pay for a service call.
Gerry :-)}
London, Canada


My customers are internal as in I'm on the inside dealing with issues inside the facility.

There has been one notable exception to my usual experiences. I have a test cell that
uses a temperature controller to cause programmed ramps of temperatures inside the test
cell.

On our older boxes, Labview running on the PC directly controls the heating system. The
newest stuff, well that was implemented by someone that isn't here anymore for many good
reasons.

Labview via a National Instruments DAQ card, changes the set point using 0-10v, the
chamber temp is read via a type J thermocouple, the scr heater controller is driven by a
4-20 MA signal from a Watlow controller. Labview needs to know what is happening so
another 0-10v output on the controller retransmits what the type J t/c on input 1 sees.

Well a month or so ago, the original controller died. It was only 5 years old but is now
out of production. So I buy something else Watlow makes and I have to wait a week for it
to be made since they can't get processor chips.

Well I get it, I install and configure it, it is working fine. Then I close the panel
door and the display winks out. FUG. It isn't a broken wire, I got a lemon. Any
vibration will reset it.

Okay fine. Try to order another one. Find out this month is the last time they are
making it. Next week the latest and greatest will be available and it costs 1/2. Well no
brainer, we can wait.

New controller shows up a day early, I stick it in, scratch my head reading the documents
and by the next day, it is working perfectly. I played with a couple parameters that
affect auto tune and that thing made a beautiful curve. Minimum overshoot, no
oscillations. Very nice. Only took about 3 trials to nail it.

Got noise problems though on process retransmit output. Prints show DAQ card wired single
ended. I check, wired diffential, AIN0 and AIN8 for those that have used a 6024E card.

Read manual for card. Insert a 3K resistor from AIN8 to AI Ground. Nice and stable now.

Pull controller, make a plate to close up the 1/8 din opening so the 1/16 din control
fits.

Wire up control, power up, I get a error that says the controller has an internal
malfunction. CHIT.

Strip the control down to boards and put back together. Fires up with input 2 error. No
chit, Input 2 should be 0-10v but the control thinks it is configured for a type J t/c.

I'm getting really good punching in the configuration by now. Call to watlow has them
telling me I have some sort of ground loop. I'll play with it tomorrow but since the
control cabinet and pc are 6 feet apart, I'm leaning to they are full of ****. I will
make sure all signal grounds are tied to a single ground in the control cabinet if they
are not already tomorrow.



Wes

I preferred Omrons or Eurotherms. Good luck.

Pete Keillor