Chart Magnification
When using a strip-chart recorder with a time base, the
chart or X-axis speed should be selected to give a con-
venient record length for a test. A record of 5 to 15
inches (125 to 375 mm) is sufficient, but it can be as
long as desired.
By the use of chart magnification, the chart time axis
can indicate the displacement of the crosshead in either a
reduced or magnified manner.
The chart magnification ratio (M) is the ratio of the chart
time axis speed to crosshead speed, that is:
Magnification Ratio (M) =
Chart Time Axis Speed
Crosshead Speed
The following example illustrates the selection of chart
time axis and crosshead speeds, and then the Magnifica-
tion Ratio required.
EXAMPLE:
Material: Nylon
% extension/minute: 100%
Ultimate extension: 50% (approximate)
Gauge length: 250 mm
Crosshead speed:
= Gauge length x % ext./min.
= 250 mm x 100%/min.
= 250 mm/min.
Chart Magnification M10-94400-1
A-14
To Next Page
Loading...
Need help?
General
