Thursday, May 14, 2009

FRF matrix - a matrix containing data points from all the FRF measurements you've made on a structure. It would be a 3D matrix where each "slice" of the matrix is a different frequency bin (f1, f2, f3...). Each entry of that "slice" is the value of each FRF at each measurement location. Ideally, this should be a symmetric matrix since m(1,2) is ALWAYS equal to m(2,1), where m(1,2) is the response at location 2 due to excitation at location 1, and m(2,1) is the response at location 1 due to excitation at location 2.

Well conditioned matrix - a matrix whose inverse is insensitive to minor changes in values. Sometimes, when you have FRFs where some of the values are very large (100k G's e.g.) and others are very small (.1G, e.g.), the inverse is very sensitive to changes in those small numbers. Since in testing, those small measurements could be near the noise floor, their values could change arbitrarily, causing problems in the inverse calculation.

Deconvolution - is an algorithm-based process used to reverse the effects of convolution on recorded data. convolution is simply when you have an input that is multiplied by a transfer function to result in a different output. Deconvolution is simply when you have the output and transfer function and work backwards to get the input.

Thursday, March 19, 2009

When tapping a hole, you will get a lip of material around the hole. To stop this from happening, use a single flute countersink and bore out (you can do this by hand with aluminum) a small bit around your hole. You can do this post tapping if you want, but then you have to run the tap through again to make sure you did not screw up the thread.

The Single Flute Countersink set is next door above all the taps. 82deg for english, 90deg for metric.

Also, MANIFOLD...I never really knew what the definition was exactly. Maybe because it has multiple ones:

For basics, a manifold is "something having many different parts or features".

In Machinery, manifold means "a chamber having several outlets through which a liquid or gas is distributed or gathered".

Tuesday, March 17, 2009

What Brad is looking for when he asks for mass properties of a system so that he can design isolation system:

If isolators are already in place, give locations of isolators relative to origin.

Clearly specify the coordinate system.

Give him the inertial properties as aligned with the output coordinate system, along with mass, distance from origin to COG, etc.

This should all be included in one easy to reference document!

Friday, March 13, 2009

Parasolid and Step Files:

These are kernels that communicate and migrate 3D surface or solid data - NONPROPRIETARY information . They do not communicate things like features or extrusions, or material content!

If you want to see for yourself, just open them up in text editor! They are saved in an ASCII format. All the numbers in this file only communicate 3D locations.

Wednesday, March 4, 2009

OK...I need a way of remembering which is single-ended and which is differential.

Single-ended is when you have one wire and compare it to ground
Differential is when you have two wires and difference the two.

...now to remember this, only one of these has a "g" in it... sinGle-ended... and that's the one that references Ground.

ECTRON AMPLIFIERS (563H)
yes they are a pain to deal with.
To zero the bridge:
1. Short the input connection(pins B and C...pin layout can be found in schematic in back of manual).
2. Put gain to 1. Adjust RTO (referred-to-output) until output is zero.
3. Put gain at 1K. Adjust RTI (referred-to-input) until output is zero.
4. Put gain back to 1... if output is not zero, do steps 2 and 3 until it is.

Wednesday, February 25, 2009

I am learning about serial communication. Baud rate is the rate of transfer (bits per second). Data is transferred one bit at a time in "packets". A packet consists of a start bit, a stop bit, the data bits, and sometimes a parity bit. The receiving device and transmitting device must have the same settings (baud rate, # data bits, etc.) to successfully send data back and forth.

Friday, February 6, 2009

Learned all about transistors and "NPN open-collector ouputs"!

Transistors consist of a base, emitter, and collector. When no current is applied through the base to the emitter, no current flows from the collector to the emitter. However, when current does flow through the base to the emitter, a proportional amount of current flows from the collector to the emitter. The relationship is: Ib = B*Ic.
So... a little base current allows a much larger collector current to flow. (B approx = 100). Oftentimes, Ic can only go so high (depending on its source power). Thus, even if Ib is very high and via the relationship Ic should be huge, Ic will only go as high as it can based on the circuit its hooked up to.

NPN open-collector output:
Now, take the idea of a transistor and put it at the output of some circuit. More specifically, connect the circuit output up the the transistor "base", connect ground to the "emitter", and leave the collector open (hence open-collector output). Now, you have a connection (the collector) that is either a short circuit or an open circuit, depending on whether the base is receiving current from the circuit.
Use this feature to hook up any other circuit you want to the collector, without worrying about affecting the internal circuit!

NPN vs PNP: these are two types of transistors. They differ in that a NPN is typically closed unless a current is applied to "base", where as PNP is open unless a current is applied to "base"