Design Realization/Detailed Design - Medical Device Design: Innovation from Concept to Market - page 159

Model / Equations:
According to Jones (2008) a first-order filter can be represented as follows:
R

V in V out

C

1
2 π

The cutoff frequency occurs at (if

RC

Refs.
Jones D (2008), Practical Electronics , Made Up Press Ltd.
Calculations:

1
2 000
1
2 000

400

π

C

Assuming a simple 1 kW resistor

C 04 . F

µ

400 π

Conclusions:
Use a simple RC circuit with R = 1 k Ω and C = 0.4 μ F
If components unavailable recalculation will be required

Checked: (if appropriate) N/A

Signature:

Name: DJC Name:

Date: 24th June 2011 Date:

You should be referring to classic textbooks for your “human” specific data and models (see
Section 5.3.1.4.1 - Biomechanics).

8.4.1 Computer-Aided Analysis
In the previous section I mentioned some typical computer-aided analysis packages. Whereas
only a few short years ago they were solely available to multinationals and universities, most
(bar a few) are within the reach of most medium enterprises and certainly, if you have a
university close by, will be in the reach of everyone.

I will try to introduce them to you shortly, but there is one important concept you need to
fully appreciate. This concept is called GIGO - “garbage in, garbage out.” Very simply, these
software packages all rely on your assumptions being correct. Hence the use of a structured
pro forma (as described previously) is essential.

There is also another trap which is commonly called painting by numbers . Because these
analyses tend to produce pictures with lots of colors, they can fool the uninitiated into making
the wrong deduction (most commonly red is bad because red is danger); or even worse