get_frame_compensation_function: get_frame_compensation_function

In tbgitoo/textureAnalyzerGels: Reading and analyzing texture analyzer data

get_frame_compensation_function

Description

Provides a compensation function that allows to estimate how much distance is lost at a given force due to TextureAnalyzer compliance. Relevant only for very hard subtrates, for hydrogels, this is typically negligeable.

Usage

get_frame_compensation_function(filename,min_force=5, max_force = 20)

Arguments

filename	Texture analyzer tab file containing compression data without sample, solely against the bench or other holder surface
min_force	Minimum force required for inclusion into slope regression region
max_force	Maximum force for inclusion into slope regression region

Details

The intended use of this function is to adjust the distance measurements to compensate for frame compliance. Indeed, frame compliance means that the set (=reported) travelling distance (motor steps) is slightly larger than the distance actually travelled by the chuck surface, a small part being lost due to frame compliance. This small part can be obtained from the Force if passed to the output function provided by the get_frame_compensation_function.

For soft samples, the frame compensation makes only a very minor difference and is not generally necessary; for very soft samples, buoyancy and capillary effects are generally more important.

Value

Distance compensation function. Takes the measured force as an argument, and indicates the equivalent chuck movement distance arising from frame compliance

Author(s)

Thomas+Marina Braschler

References

Filtering in the Time and Frequency Domains, Herman J. Blinchikoff, Anatol I. Zverev, Wiley, 1976

Examples

# Get the frame compensation function
path=system.file("sampleData",package="textureAnalyzerGels")
frame_compensation_function=get_frame_compensation_function(paste(path,"frame_stiffness.tab",sep="/"))

# Comparative plotting
data(sampleGel)
frame_stiffness = read_texture_analyzer_tab(paste(path,"frame_stiffness.tab",sep="/"),chuck_diameter=4e-3)
frame_stiffness_smooth=smooth_texture_analyzer_data(frame_stiffness, sd = 0.005,lm_region_upper_mm=0.05)
touch_point_frame_compensation=find_initial_touch_point(frame_stiffness_smooth)

plot(pressure ~ Distance, sampleGel,type="l",xlim=c(0,start_height_mm+0.5),main="Frame stiffness compensation",xlab="Distance [mm]", ylab="Stress [Pa]")
# This is the corresponding plot without sample
lines(frame_stiffness$Distance-touch_point_frame_compensation+start_height_mm, frame_stiffness$pressure,type="l",lty=2)
# Frame compensation
sampleGel$Distance_compensated = sampleGel$Distance-frame_compensation_function(sampleGel$Force)
lines(pressure ~ Distance_compensated, sampleGel,type="l",col="red")
# Frame compensation on the frame compensation measurement
frame_stiffness$Distance_compensated = frame_stiffness$Distance-frame_compensation_function(frame_stiffness$Force)
lines(frame_stiffness$Distance_compensated-touch_point_frame_compensation+start_height_mm, frame_stiffness$pressure,type="l",lty=2, col="red")

legend("topleft",legend=c("sample Gel","sample Gel compensated", "no sample control","no sample control compensated"), lty=c(1,1,2,2), col=c("black","red","black","red"))

tbgitoo/textureAnalyzerGels documentation built on March 30, 2022, 4:53 a.m.