On July 22, 1999 spex was in its cold with the arrray focus motor attached. The page catalogs the data taken (steps &. voltage)
for the array focus mechanism.

1. How the data was obtained

The testStepper program's afocdata command was used to obtained the data. The measurement were obtained using the following method:

1.Positioned the mechanism to near 0 volts.
2. Run the testStepper's afocdata command, this command:
a. Sets the step counter set to 0.
b. at 5000 step intervals, the steps and voltage were recorded.
c. The recorded voltages are a mean of 5 samples from the AD16 IO board..
d. Format of the data line is: step mean_voltage std_voltage

These are the data files:

p1.dat - 1st set of positive voltage data. The mechanism ran into the limit after the 270000 step. All subsequent data was taken with max range of 255000 steps.
p2.dat - 2nd set of positive voltage data.
p3.dat - 2nd set of positive voltage data.
n1.dat - 1st set of negative voltage data.
n2.dat - 2nd set of negative voltage data.

2 Steps to volts equation

p1.skv was imported into regression program to obtain these coefficients:
Here coefficients for volts = f(step) for steps > 0.

a = 0.001953205923
b = 4.538756574e-6
c = -4.55124946e-13
d = 7.903804145e-17
e = -2.508697361e-22
f = 8.193271635e-28

p1.gp are the gunplot commands to plot the data & equation to a postscript file: p1.ps.
Here is the resulting PDF file: p1.pdf

n1.skv was imported into regression program to obtain these coefficients:
Here coefficients for volt = f(step) for step < 0.

a = 0.001593641981
b = 4.528740177e-6
c = 3.24032633e-12
d = 6.032176048e-17
e = 1.563936665e-22
f = 5.104790413e-28

n1.gp are the gunplot commands to plot the data & equation to a postscript file: n1.ps
Here is the resulting PDF file: n1.pdf

3. volts to steps

The xy axis were transposed to calculate the volts->steps.

p1_t.skv is the data from p1.dat with the x & y axis transposed.
4th degree polynomial fits best:
Here are the coefficients for steps = f(volts) for step > 0.

a = -1327.810288
b = 239170.8823
c = -91772.00397
d = 19778.22023
e = -1689.306409

p1_t.gp are the gunplot commands to plot the data & equation to a postscript file: p1_t.ps
Here is the resulting PDF file: p1_t.pdf

n1_t.skv is the data from n1.dat with the x & y axis transposed.
3rd degree polynomial fits best.
Here are the coefficients for steps = f(volts) for step < 0.

a = 2260.528447
b = 251532.1734
c = 78517.77997
d = 9591.936856

n1_t.gp are the gunplot commands to plot the data & equation to a postscript file: n1_t.ps
Here is the resulting PDF file: n1_t.pdf

Note:

The y = f( x ) represents a Nth degree polynomial fit. The equations would look like:

y = a + xb + x²c + x³d + x⁴e + ...

4. Cold vs Warm

After the dewar warmup, I took new mesurement of Volts vs Steps for the Array Focus. Here is the data for the warm dewar. warm.dat To compared it to the code data, I combine p1.dat and n1.dat into cold.dat. Here is the graphs as a postscript warm.ps or PDF warm.pdf.

I also compared the data fit on the grating's home sensor for warm and cold: grating_cold.dat and grating_warm.dat.
Here is a graph as grating.ps or PDF grating.pdf.

Written by Tony Denault.