Daily Archives: Thursday, 29-Jan-2004

Nothing Will Evolve in Georgia

I moved to Georgia from Tennessee almost two years ago. I like living here a lot more than I thought I ever would and for now I consider this my home until I die. I’m happy here. I’m just not happy with everything happening here.

It seems that from here on out Kathy Cox, our state schools superintendent, doesn’t want things to continue to evolve here. She want them to "biologically change over time". I’m not joking.

New middle and high school science standards proposed by state Schools Superintendent Kathy Cox strike references to "evolution" and replace them with the term “biological changes over time,” a revision critics say will further weaken learning in a critical subject.

Now, for the most part, these new proposed standards are a step forward for Georgia. The change in the state wide curriculum is something that has been needed for some time. However, this one little deference to the creationist crowd is a big step backwards and a stumbling block for getting this improved curriculum approved. I’m hoping it gets ammended in the next few days. Kathy Cox isn’t commenting on it publicly as of this morning.

Choosing the Proper Sensor.


Okay, I know I said monday that I would make some comments on proximity switches and photoeyes “tomorrow” and that that tomorrow was yesterday. Between seasonal depression due to cold wet weather and some other items I needed to take care of it didn’t get done. I’m still working on it.

What brought this up was the customer I was working with had some bad experiences with the proximity switches they were using prior to this equipment upgrade and decided to use only photoeyes on the upgrade. That’s sort of like saying that you’ve had bad luck using open-end wrenches in the past and you are only going to use boxed-end wrenches in the future. Both will tighten and loosen a nut but there are applications where either one will be inappropriate.

Proximity switches are great for locating an object in a small specific area where photo eyes are great for finding out if a boundry has been crossed. Each type of sensor can be broken down into a dozen or more specific sensors for a very specific job.

Proximity switches can work off of inductance or capacitance. Inductive proximity switches are only going to be able to sense metallic objects while capacitance type sensors can detect almost anything.

Photoeyes can be broken down into multiple groups. Through photoeyes use an emmiter and a reciever mounted opposite of each other and provide a clearly defined line that it will sense objects crossing. Reflective photoeyes use their emmited light reflected back to them from a reflector to indicate a "clear" condition and are useful when a clearly defined line isn’t necessary and the objects being sensed may have holes that a through photoeye could "look" through. Diffuse photoeyes use reflective light to indicate a "blocked" condition. Light reflected back from the object being sensed is how these work.

The thing is that these are specialty devices that need to be chosen based on the application. If you are having problems with photoeyes or proximity switches in your application it is likely that the proper devices was never specified. The makers of these devices, like Banner Engineering or IFM Efector, are very good at helping you choose the device suitible for your sensing needs. Listen to their advice.

Oh, and when a controls engineer that has been specifiying sensors for the last eighteen years tells you you need to use a prox instead of a photo eye for an application, listen to him.


French cabinet backs scarf ban


There have been misguided attempts in the US by school administrators attempting to remove individual student’s rights to wear clothing or jewelry showing ones religious affiliation. This is usually over their misinterpretation of the seperation of Church and State. In France it looks like this policy may become the national law.

Now, the French can do what they want to do, they are a sovereign country and it’s citizens do have a say in who is making these laws, but I believe this is going to cause them more problems than it is going to resolve.